0001692115-22-000005 | 10-K | XBRL Viewer | Southwest GAS Holdings INC

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CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Regulated operations plant:
Gas plant	$ 8,901,575	$ 8,384,000
Less: accumulated depreciation	(2,538,508)	(2,419,348)
Construction work in progress	183,485	211,429
Net regulated operations plant	6,546,552	6,176,081
Other property and investments	153,093	143,611
Current assets:
Cash and cash equivalents	38,691	41,070
Accounts receivable, net of allowances	510,800	146,861
Accrued utility revenue	84,900	82,400
Income taxes receivable, net	7,826	11,155
Deferred purchased gas costs	291,145	2,053
Prepaid and other current assets	242,243	152,748
Total current assets	835,502	436,287
Noncurrent assets:
Goodwill	10,095	10,095
Deferred income taxes	121	455
Deferred charges and other assets	405,021	490,562
Total noncurrent assets	415,116	500,657
Total assets	7,950,263	7,256,636
Capitalization:
Common stock	49,112	49,112
Additional paid-in capital	1,618,911	1,410,345
Accumulated other comprehensive loss, net	(46,913)	(61,135)
Retained earnings	906,827	835,146
Total Southwest Gas Holdings, Inc. equity	2,527,937	2,233,468
Redeemable noncontrolling interests	196,717	165,716
Long-term debt, less current maturities	2,440,603	2,438,206
Total capitalization	4,968,540	4,671,674
Commitments and contingencies (Note 10)
Current liabilities:
Current maturities of long-term debt	275,000	0
Short-term debt	250,000	57,000
Accounts payable	234,070	161,646
Customer deposits	56,127	67,920
Income taxes payable, net	6,734	12,556
Accrued general taxes	53,064	48,640
Accrued interest	22,926	20,495
Deferred purchased gas costs	0	54,636
Other current liabilities	146,422	146,046
Total current liabilities	1,037,609	556,525
Deferred income taxes and other credits:
Deferred income taxes and investment tax credits, net	638,828	581,100
Accumulated removal costs	424,000	404,000
Other deferred credits and other long-term liabilities	881,286	1,043,337
Total deferred income taxes and other credits	1,944,114	2,028,437
Total capitalization and liabilities	$ 7,950,263	$ 7,256,636

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Common stock, par (in USD per share)	$ 1	$ 1
Common stock, authorized (in shares)	120,000,000	120,000,000
Common stock, issued (in shares)	60,422,081	57,192,925
Common stock, outstanding (in shares)	60,422,081	57,192,925

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating revenues:
Gas operating revenues	$ 1,521,790	$ 1,350,585	$ 1,368,939
Utility infrastructure services revenues	2,158,661	1,948,288	1,750,978
Total operating revenues	3,680,451	3,298,873	3,119,917
Operating expenses:
Net cost of gas sold	430,907	342,837	385,164
Operations and maintenance	438,550	406,382	422,174
Depreciation and amortization	253,398	235,295	215,620
Taxes other than income taxes	80,343	63,460	62,328
Utility infrastructure services expenses	1,955,467	1,729,429	1,573,227
Total operating expenses	1,203,198	1,047,974	1,085,286
Operating income	318,592	302,611	283,653
Other income and (expenses):
Net interest deductions	(97,560)	(101,148)	(95,026)
Other income (deductions)	(4,559)	(6,590)	9,517
Total other income and (expenses)	(102,119)	(107,738)	(85,509)
Income before income taxes	216,473	194,873	198,144
Income tax expense	29,338	35,755	34,973
Net income	187,135	159,118	163,171
Net income attributable to noncontrolling interests	6,423	6,661	2,711
Net income attributable to Southwest Gas Holdings, Inc.	$ 200,779	$ 232,324	$ 213,936
Earnings per share:
Basic (in USD per share)	$ 3.39	$ 4.15	$ 3.94
Diluted (in USD per share)	$ 3.39	$ 4.14	$ 3.94
Weighted average shares:
Basic (in shares)	59,145	55,998	54,245
Diluted (in shares)	59,259	56,076	54,312

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 187,135	$ 159,118	$ 163,171
Defined benefit pension plans:
Net actuarial gain (loss)	44,974	(43,730)	(54,026)
Amortization of prior service cost	729	878	966
Amortization of net actuarial loss	33,894	28,751	17,766
Prior service cost	0	0	(1,426)
Regulatory adjustment	(67,027)	5,650	28,077
Net defined benefit pension plans	12,570	(8,451)	(8,643)
Forward-starting interest rate swaps (“FSIRS”):
Amounts reclassified into net income	1,652	2,467	2,541
Net forward-starting interest rate swaps	1,652	2,467	2,541
Foreign currency translation adjustments	20	1,713	2,038
Total other comprehensive income (loss), net of tax	14,222	(5,984)	(6,102)
Comprehensive income	201,357	153,134	157,069
Comprehensive income attributable to noncontrolling interests	6,423	6,661	2,711
Comprehensive income attributable to Southwest Gas Holdings, Inc.	$ 215,021	$ 228,053	$ 209,872

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	$ 187,135	$ 159,118	$ 163,171
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	253,398	235,295	215,620
Deferred income taxes	53,237	44,997	33,681
Changes in current assets and liabilities:
Accounts receivable, net of allowances	(22,806)	3,933	(10,737)
Accrued utility revenue	(2,500)	(3,300)	(1,900)
Deferred purchased gas costs	(343,728)	36,239	(58,491)
Accounts payable	57,764	9,618	(27,473)
Accrued taxes	7,753	(1,527)	8,895
Other current assets and liabilities	(70,271)	48,545	89,171
Gains on sale of equipment	(6,906)	(1,848)	(5,473)
Changes in undistributed stock compensation	6,392	5,294	5,146
Equity AFUDC	0	(4,724)	(4,161)
Changes in deferred charges and other assets	(28,743)	(44,291)	(31,767)
Changes in other liabilities and deferred credits	(72,386)	(65,136)	(13,361)
Net cash provided by operating activities	25,245	424,061	367,794
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(601,983)	(692,216)	(778,748)
Acquisition of businesses, net of cash acquired	(2,354,260)	0	(47,638)
Changes in customer advances	15,973	14,033	19,001
Other	(32)	771	(95)
Net cash used in investing activities	(586,042)	(677,412)	(759,842)
CASH FLOW FROM FINANCING ACTIVITIES:
Issuance of common stock, net	213,641	139,245	157,946
Dividends paid	(111,400)	(104,500)	(95,900)
Issuance of long-term debt, net	297,318	446,508	297,222
Retirement of long-term debt	0	(125,000)	0
Change in credit facility and commercial paper	(20,000)	0	0
Change in short-term portion of credit facilities	(48,000)	(104,000)	59,000
Issuance of short-term debt	1,850,000	0	0
Withholding remittance – share-based compensation	(1,263)	(2,736)	(1,858)
Other	(1,820)	(1,262)	(825)
Net cash provided by financing activities	558,418	253,932	400,575
Effects of currency translation on cash and cash equivalents	160	228	158
Change in cash and cash equivalents	(2,379)	581	8,527
Cash and cash equivalents at beginning of period	41,070	40,489	31,962
Cash and cash equivalents at end of period	38,691	41,070	40,489
SUPPLEMENTAL INFORMATION:
Interest paid, net of amounts capitalized	90,240	96,726	88,658
Income taxes paid (received), net	$ (13,529)	$ (19,603)	$ 678

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Southwest Gas Holdings, Inc.	Common Stock	Additional paid-in capital	Accumulated other comprehensive loss	Retained earnings	Noncontrolling interest
Beginning balance (in shares) at Dec. 31, 2018			53,026,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)			1,981,000
Ending balance (in shares) at Dec. 31, 2019			47,482,000
Beginning balance at Dec. 31, 2018			$ 54,656	$ 1,065,242	$ (49,049)	$ 717,155	$ (452)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances			1,981	161,620
Change in ownership of noncontrolling interest				(452)			452
Foreign currency exchange translation adjustment					2,038
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax					(8,643)
FSIRS amounts reclassified to net income, net of tax	$ 2,541				2,541
Net income (loss)						163,171
Dividends declared						(97,600)
Ending balance at Dec. 31, 2019	$ 2,005,152	$ 2,505,914	$ 49,112	1,229,083	(55,151)	782,108	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 2,180
Common stock issuances (in shares)			2,186,000
Ending balance (in shares) at Dec. 31, 2020	57,192,925		47,482,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances			$ 2,186	142,218
Foreign currency exchange translation adjustment					1,713
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax					(8,451)
FSIRS amounts reclassified to net income, net of tax	$ 2,467				2,467
Net income (loss)						159,118
Redemption value adjustment	74,513					(74,513)
Dividends declared						(105,300)
Ending balance at Dec. 31, 2020	$ 2,233,468	2,674,953	$ 49,112	1,410,345	(61,135)	835,146	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 2,280
Common stock issuances (in shares)			3,229,000
Ending balance (in shares) at Dec. 31, 2021	60,422,081		47,482,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances			$ 3,229	219,298
Promissory notes in association with redeemable noncontrolling interest	$ (4,237)
Foreign currency exchange translation adjustment					20
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax					12,570
FSIRS amounts reclassified to net income, net of tax	1,652				1,652
Net income (loss)						187,135
Redemption value adjustment	12,016					(12,016)
Dividends declared						(114,600)
Ending balance at Dec. 31, 2021	$ 2,527,937	$ 2,953,820	$ 49,112	$ 1,618,911	$ (46,913)	$ 906,827	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 2,380

CONSOLIDATED BALANCE SHEETS - Southwest - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Regulated operations plant:
Gas plant	$ 8,901,575	$ 8,384,000
Less: accumulated depreciation	(2,538,508)	(2,419,348)
Construction work in progress	183,485	211,429
Net regulated operations plant	6,546,552	6,176,081
Other property and investments	153,093	143,611
Current assets:
Cash and cash equivalents	38,691	41,070
Accounts receivable, net of allowances	510,800	146,861
Accrued utility revenue	84,900	82,400
Income taxes receivable, net	7,826	11,155
Deferred purchased gas costs	291,145	2,053
Receivable from parent	15,166	13,956
Prepaid and other current assets	242,243	152,748
Total current assets	835,502	436,287
Noncurrent assets:
Goodwill	10,095	10,095
Deferred charges and other assets	405,021	490,562
Total noncurrent assets	415,116	500,657
Total assets	7,950,263	7,256,636
Capitalization:
Common stock	49,112	49,112
Additional paid-in capital	1,618,911	1,410,345
Accumulated other comprehensive loss, net	(46,913)	(61,135)
Retained earnings	906,827	835,146
Total Southwest Gas Holdings, Inc. equity	2,527,937	2,233,468
Long-term debt, less current maturities	2,440,603	2,438,206
Total capitalization	4,968,540	4,671,674
Commitments and contingencies (Note 10)
Current liabilities:
Current maturities of long-term debt	275,000	0
Short-term debt	250,000	57,000
Accounts payable	234,070	161,646
Customer deposits	56,127	67,920
Accrued general taxes	53,064	48,640
Accrued interest	22,926	20,495
Deferred purchased gas costs	0	54,636
Payable to parent	0	142
Other current liabilities	146,422	146,046
Total current liabilities	1,037,609	556,525
Deferred income taxes and other credits:
Deferred income taxes and investment tax credits, net	638,828	581,100
Accumulated removal costs	424,000	404,000
Other deferred credits and other long-term liabilities	881,286	1,043,337
Total deferred income taxes and other credits	1,944,114	2,028,437
Total capitalization and liabilities	$ 7,950,263	$ 7,256,636

CONSOLIDATED STATEMENTS OF INCOME - Southwest - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Gas operating revenues	$ 1,521,790	$ 1,350,585	$ 1,368,939
Operating expenses:
Net cost of gas sold	430,907	342,837	385,164
Operations and maintenance	438,550	406,382	422,174
Depreciation and amortization	253,398	235,295	215,620
Taxes other than income taxes	80,343	63,460	62,328
Total operating expenses	1,203,198	1,047,974	1,085,286
Operating income	318,592	302,611	283,653
Other income and (expenses):
Interest Expense	(97,560)	(101,148)	(95,026)
Other income (deductions)	(4,559)	(6,590)	9,517
Total other income and (expenses)	(102,119)	(107,738)	(85,509)
Income before income taxes	216,473	194,873	198,144
Income tax expense	29,338	35,755	34,973
Net income	$ 187,135	$ 159,118	$ 163,171

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - Southwest - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net income	$ 187,135	$ 159,118	$ 163,171
Defined benefit pension plans:
Net actuarial gain (loss)	44,974	(43,730)	(54,026)
Amortization of prior service cost	729	878	966
Amortization of net actuarial loss	33,894	28,751	17,766
Prior service cost	0	0	(1,426)
Regulatory adjustment	(67,027)	5,650	28,077
Net defined benefit pension plans	12,570	(8,451)	(8,643)
Forward-starting interest rate swaps (“FSIRS”):
FSIRS amounts reclassified to net income, net of tax	1,652	2,467	2,541
Net forward-starting interest rate swaps	1,652	2,467	2,541
Total other comprehensive income (loss), net of tax	14,222	(5,984)	(6,102)
Comprehensive income	$ 201,357	$ 153,134	$ 157,069

CONSOLIDATED STATEMENTS OF CASH FLOWS - Southwest - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	$ 187,135	$ 159,118	$ 163,171
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	253,398	235,295	215,620
Deferred income taxes	53,237	44,997	33,681
Changes in current assets and liabilities:
Accounts receivable, net of allowances	(22,806)	3,933	(10,737)
Accrued utility revenue	(2,500)	(3,300)	(1,900)
Deferred purchased gas costs	(343,728)	36,239	(58,491)
Accounts payable	57,764	9,618	(27,473)
Accrued taxes	7,753	(1,527)	8,895
Other current assets and liabilities	(70,271)	48,545	89,171
Changes in undistributed stock compensation	6,392	5,294	5,146
Equity AFUDC	0	(4,724)	(4,161)
Changes in deferred charges and other assets	(28,743)	(44,291)	(31,767)
Changes in other liabilities and deferred credits	(72,386)	(65,136)	(13,361)
Net cash provided by operating activities	25,245	424,061	367,794
CASH FLOW FROM INVESTING ACTIVITIES:
Payments to Acquire Property, Plant, and Equipment	(601,983)	(692,216)	(778,748)
Changes in customer advances	15,973	14,033	19,001
Other	(32)	771	(95)
Net cash used in investing activities	(586,042)	(677,412)	(759,842)
CASH FLOW FROM FINANCING ACTIVITIES:
Contributions from parent	202,583	177,922	159,936
Dividends paid	(111,400)	(104,500)	(95,900)
Issuance of long-term debt, net	297,318	446,508	297,222
Retirement of long-term debt	0	(125,000)	0
Change in credit facility and commercial paper	(20,000)	0	0
Change in short-term portion of credit facilities	193,000	(137,000)	42,000
Withholding remittance – share-based compensation	(1,263)	(2,736)	(1,858)
Other	(1,820)	(1,262)	(825)
Net cash provided by financing activities	558,418	253,932	400,575
Change in cash and cash equivalents	(2,379)	581	8,527
Cash and cash equivalents at beginning of period	41,070	40,489	31,962
Cash and cash equivalents at end of period	38,691	41,070	40,489
SUPPLEMENTAL INFORMATION:
Interest paid, net of amounts capitalized	90,240	96,726	88,658
Income taxes paid (received), net	$ (13,529)	$ (19,603)	$ 678

CONSOLIDATED STATEMENTS OF EQUITY - Southwest - USD ($) $ in Thousands	Total	Common Stock	Additional paid-in capital	Accumulated other comprehensive loss	Retained earnings
Common stock, outstanding (in shares)		53,026,000
Beginning balance at Dec. 31, 2018		$ 54,656	$ 1,065,242	$ (49,049)	$ 717,155
Share-based compensation			3,905		(618)
Contributions from Southwest Gas Holdings, Inc.			159,936
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax				(8,643)
FSIRS amounts reclassified to net income, net of tax	$ 2,541			2,541
Net income					163,171
Dividends declared to Southwest Gas Holdings, Inc.					(97,600)
Ending balance at Dec. 31, 2019	2,005,152	$ 49,112	1,229,083	(55,151)	782,108
Common stock, outstanding (in shares)		47,482,000
Share-based compensation			3,340		(780)
Contributions from Southwest Gas Holdings, Inc.			177,922
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax				(8,451)
FSIRS amounts reclassified to net income, net of tax	2,467			2,467
Net income					159,118
Dividends declared to Southwest Gas Holdings, Inc.					(105,300)
Ending balance at Dec. 31, 2020	$ 2,233,468	$ 49,112	1,410,345	(61,135)	835,146
Common stock, outstanding (in shares)	57,192,925	47,482,000
Share-based compensation			5,983		(854)
Contributions from Southwest Gas Holdings, Inc.			202,583
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax				12,570
FSIRS amounts reclassified to net income, net of tax	$ 1,652			1,652
Net income					187,135
Dividends declared to Southwest Gas Holdings, Inc.					(114,600)
Ending balance at Dec. 31, 2021	$ 2,527,937	$ 49,112	$ 1,618,911	$ (46,913)	$ 906,827
Common stock, outstanding (in shares)	60,422,081	47,482,000

- Definition

Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
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+ Details

Background, Organization, and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Background, Organization, and Summary of Significant Accounting Policies

Note 1 - Background, Organization, and Summary of Significant Accounting Policies

Nature of Operations. This is a combined annual report of Southwest Gas Holdings, Inc. and its subsidiaries (the “Company”) and Southwest Gas Corporation and its subsidiaries (“Southwest” or the “natural gas distribution” segment). The notes to the consolidated financial statements apply to both entities. Southwest Gas Holdings, Inc., a Delaware corporation, is a holding company, owning all of the shares of common stock of Southwest, all of the shares of common stock of Centuri Group, Inc. (“Centuri” or the “utility infrastructure services” segment), and all of the membership interests in the newly acquired Dominion Energy Questar Pipeline, LLC and related entities through the newly formed entity, MountainWest Pipelines Holding Company (herein referred to interchangeably as “Questar Pipelines” or “MountainWest”). Questar Pipelines is a third segment, referred to as the “pipeline and storage” segment. Southwest was previously referred to as the natural gas operations segment; with the addition of the Questar Pipelines natural gas interstate transmission and storage services, Southwest, primarily consisting of intrastate natural gas service to customers, will be referred to as indicated above.

In October 2021, the Company entered into an agreement with Dominion Energy Questar Corporation, a wholly owned subsidiary of Dominion Energy, Inc., to acquire all equity interests in Questar Pipelines. On December 31, 2021, the Company completed the acquisition of Questar Pipelines. As a result of the acquisition closing on December 31, 2021, the Company’s Consolidated Statements of Income and Consolidated Statements of Cash Flows do not reflect results of operations or operating activities of Questar Pipelines otherwise occurring during 2021. Subsequent to the completion of the acquisition, and as noted above, the Company formed MountainWest, a wholly owned subsidiary, owning all of the membership interests in Questar Pipelines. Questar Pipelines, and the businesses underlying it, will be renamed under the MountainWest branding in the first half of 2022. See Note 15 - Business Acquisitions for additional information. The acquired operations further diversify the Company’s business in the midstream sector, with an expansion of interstate natural gas pipelines and underground storage services, primarily composed of regulated operations under the jurisdiction of the Federal Energy Regulatory Commission (the “FERC”), thereby expanding natural gas transportation services into Utah, Wyoming, and Colorado. The total consideration for the acquisition was $1.576 billion, including transaction costs paid on behalf of the seller and an estimated post-closing payment. The Company initially financed the purchase of this acquisition with a $1.6 billion draw under the 364-day term loan entered into in November 2021. See Note 8 - Debt for more information.

On March 1, 2022, the Company announced that its Board of Directors (the “Board”) determined to separate Centuri from Southwest Gas Holdings, Inc. and has authorized management to complete the separation within the next nine to twelve months. Management intends to evaluate various alternatives to determine the optimal structure to maximize stockholder value. Depending on the form the separation takes, it will likely be subject to a number of conditions.

Southwest is engaged in the business of purchasing, distributing, and transporting natural gas for customers in portions of Arizona, Nevada, and California. Public utility rates, practices, facilities, and service territories of Southwest are subject to regulatory oversight. The timing and amount of rate relief can materially impact results of operations. Natural gas purchases and the timing of related recoveries can materially impact liquidity. Results for the natural gas distribution segment are higher during winter periods due to the seasonality incorporated in its regulatory rate structures.

Centuri is a strategic utility infrastructure services company dedicated to partnering with North America’s gas and electric providers to build and maintain the energy network that powers millions of homes across the United States (“U.S.”) and Canada. Centuri derives revenue primarily from installation, replacement, repair, and maintenance of energy networks. Centuri operations are generally conducted under the business names of NPL Construction Co. (“NPL”), NPL Canada Ltd. (“NPL Canada”), New England Utility Constructors, Inc. (“Neuco”), Linetec Services, LLC (“Linetec”), and Riggs Distler & Company, Inc. (“Riggs Distler”). Utility infrastructure services activity is seasonal in many of Centuri’s operating areas. Peak periods are the summer and fall months in colder climate areas, such as the northeastern and midwestern U.S. and in Canada. In warmer climate areas, such as the southwestern and southeastern U.S., utility infrastructure services activity continues year round. Centuri completed the acquisition of Drum Parent LLC, formerly Drum Parent, Inc. (“Drum”), including Drum’s most significant operating subsidiary, Riggs Distler, in August 2021, thereby expanding Centuri’s electric infrastructure services footprint in the northeast and mid-Atlantic regions of the U.S. See Note 15 - Business Acquisitions for more information.

MountainWest includes Dominion Energy Questar Pipeline, LLC, along with its subsidiary, Dominion Energy Overthrust Pipeline, LLC, and an equity interest in White River Hub, LLC, which is not consolidated, along with non-regulated businesses providing analytical and measurement services, and natural gas gathering.

Basis of Presentation. The Company follows accounting principles generally accepted in the United States (“U.S. GAAP”) in accounting for all of its businesses. Unless specified otherwise, all amounts are in U.S. dollars. Accounting for regulated operations conforms with U.S. GAAP as applied to rate-regulated companies and as prescribed by federal agencies and commissions of the various states in which the rate-regulated companies operate. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets

and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Consolidation. The accompanying financial statements are presented on a consolidated basis for Southwest Gas Holdings, Inc. and all subsidiaries and Southwest Gas Corporation and all subsidiaries as of December 31, 2021 (except those accounted for using the equity method as discussed below). All significant intercompany balances and transactions have been eliminated with the exception of transactions between Southwest and Centuri in accordance with accounting treatment for rate-regulated entities.

Centuri, through its subsidiaries, holds a 50% interest in W.S. Nicholls Western Construction Ltd. (“Western”), a Canadian infrastructure services company that is a variable interest entity. Centuri determined that it is not the primary beneficiary of the entity due to a shared-power structure; therefore, Centuri does not consolidate the entity and has recorded its investment, and results related thereto, using the equity method. The investment in Western, related earnings, and dividends received from Western in 2021 and 2020 were not significant. Centuri’s maximum exposure to loss as a result of its involvement with Western was estimated at $12.6 million as of December 31, 2021.

MountainWest, through its subsidiaries, holds a 50% noncontrolling interest in White River Hub, LLC, a FERC-regulated transporter of natural gas with facilities that connect with six interstate pipeline systems and a major processing plant in Colorado. As noted above, Questar Pipelines does not consolidate the entity and has recorded its investment using the equity method. The investment in White River Hub is approximately $25.6 million, the related proportional earnings and dividends for which are not expected to be significant to the Company. The investment is included in Other property and investments on the Company’s Consolidated Balance Sheet at December 31, 2021.

Fair Value Measurements. Certain assets and liabilities are reported at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.

U.S. GAAP states that a fair value measurement should be based on the assumptions that market participants would use in pricing the asset or liability and establishes a fair value hierarchy that ranks the inputs used to measure fair value by their reliability. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to fair values derived from unobservable inputs (Level 3 measurements). Financial assets and liabilities are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement. The three levels of the fair value hierarchy are as follows:

Level 1 – quoted prices (unadjusted) in active markets for identical assets or liabilities that a company has the ability to access at the measurement date.

Level 2 – inputs other than quoted prices included within Level 1 that are observable for similar assets or liabilities, either directly or indirectly.

Level 3 – unobservable inputs for the asset or liability. Unobservable inputs are used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at the measurement date.

The Company primarily used quoted market prices and other observable market pricing information (exclusive of purchase accounting adjustments as noted in Note 15 - Business Acquisitions) in valuing cash and cash equivalents, long-term debt outstanding, and assets of the qualified pension plan and the postretirement benefits other than pensions required to be recorded and/or disclosed at fair value. The Company uses prices and inputs that are current as of the measurement date, and recognizes transfers between levels at either the actual date of an event or a change in circumstance that caused the transfer.

Net Regulated Operations Plant. Net regulated operations plant includes gas plant at original cost, less the accumulated provision for depreciation and amortization, plus any unamortized balance of acquisition adjustments. Original cost generally includes contracted services, material, payroll, and related costs such as taxes and certain benefits, general and administrative expenses, and an allowance for funds used during construction, less contributions in aid of construction. See also Depreciation and Amortization below.

Other Property and Investments. Other property and investments on Southwest’s and the Company’s Consolidated Balance Sheets includes:


	December 31,
(Thousands of dollars)	2021		2020
Net cash surrender value of COLI policies	$	149,947	$	140,874
Other property	3,146		2,737
Total Southwest Gas Corporation	153,093		143,611
Non-regulated property, equipment, and intangibles	1,616,392		1,089,414
Non-regulated accumulated provision for depreciation and amortization	(512,343)		(422,741)
Other property and investments	59,337		23,961
Total Southwest Gas Holdings, Inc.	$	1,316,479	$	834,245

Included in the table above are the net cash surrender values of company-owned life insurance (“COLI”) policies. These life insurance policies on members of management and other key employees are used by Southwest to indemnify itself against the loss of talent, expertise, and knowledge, as well as to provide indirect funding for certain nonqualified benefit plans. The term non-regulated in regard to assets and related balances in the table above is in reference to the non-rate regulated operations of Centuri, and to a more limited extent, MountainWest.

Intangible Assets. Intangible assets (other than goodwill) are amortized using the straight-line method to reflect the pattern of economic benefits consumed over the estimated periods benefited. The recoverability of intangible assets is evaluated when events or circumstances indicate that a revision of estimated useful lives is warranted or that an intangible asset may be impaired. These intangible assets are included in Other property and investments on the Company’s Consolidated Balance Sheets. Centuri’s intangible assets (other than goodwill) have finite lives and are associated with businesses previously acquired (including Riggs Distler). The balances at December 31, 2021 and 2020, respectively, were as follows:


	December 31, 2021
(Thousands of dollars)	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Customer relationships	$	393,834	$	(42,886)	$	350,948
Trade name and trademarks	79,650		(7,093)		72,557
Customer contracts backlog	4,500		(1,500)		3,000
Total	$	477,984	$	(51,479)	$	426,505

	December 31, 2020
Customer relationships	$	154,757	$	(29,237)	$	125,520
Trade name and trademarks	23,618		(8,954)		14,664
Customer contracts backlog	270		(270)		—
Noncompete agreements	1,931		(1,931)		—
Total	$	180,576	$	(40,392)	$	140,184

Amortization expense for the acquired intangible assets listed above for the years ended December 31, 2021, 2020, and 2019 was $17.3 million, $10.8 million, and $10.7 million, respectively.

The estimated future amortization of the intangible assets for the next five years and thereafter is as follows:


(Thousands of dollars)
2022	$	29,814
2023	26,814
2024	26,814
2025	26,769
2026	26,580
Thereafter	289,714
Total	$	426,505

See Note 2 - Regulated Operations Plant and Leases for additional information regarding natural gas distribution intangible assets.

Cash and Cash Equivalents. For purposes of reporting consolidated cash flows, cash and cash equivalents include cash on hand and financial instruments with original maturities of three months or less. Such investments are carried at cost, which approximates market value. Cash and cash equivalents of the Company include $20 million of money market fund investments at December 31, 2021, and an insignificant amount at December 31, 2020. The money market fund investments for Southwest were insignificant at both balance sheet dates. These investments fall within Level 2 of the fair value hierarchy, due to the asset valuation methods used by money market funds.

Typical non-cash investing activities for the Company and Southwest include capital expenditures that were not paid as of year end that are included in accounts payable totaling approximately $19.4 million. Additionally for Southwest, non-cash investing activities include customer advances applied as contributions toward utility construction activity, such amounts were not significant for the periods presented herein. Also, see Note 2 - Regulated Operations Plant and Leases for information related to right-of-use (“ROU”) assets obtained in exchange for lease liabilities, which are non-cash investing and financing activities. ROU assets and lease liabilities are also subject to non-cash impacts as a result of other factors, such as lease terminations and modifications.

Income Taxes. The asset and liability method of accounting is utilized for the recognition of income taxes. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are anticipated to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the enactment date. For regulatory and financial reporting purposes, investment tax credits (“ITC”) related to gas utility operations are deferred and amortized over the life of related fixed assets. As of December 31, 2021, the Company had cumulative book earnings of approximately $59 million in its foreign jurisdiction. Management previously asserted and continues to assert that all the earnings of Centuri’s Canadian subsidiaries will be permanently reinvested in Canada. As a result, no U.S. deferred income taxes have been recorded related to cumulative foreign earnings.

The Financial Accounting Standards Board (the “FASB”) issued guidance to allow an accounting policy election of either (i) treating taxes attributable to future taxable income related to Global Intangible Low-Taxed Income (“GILTI”) as a current period expense when incurred or (ii) recognizing deferred taxes for temporary differences expected to reverse as GILTI in future years. The Company has elected to treat GILTI as a current period cost when incurred and has considered the estimated 2021 GILTI impact, which was immaterial, to its 2021 tax expense.

Deferred Purchased Gas Costs. The various regulatory commissions have established procedures to enable the rate-regulated companies to adjust billing rates for changes in the cost of natural gas purchased. The difference between the current cost of gas purchased and the cost of gas recovered in billed rates is deferred. Generally, these deferred amounts are recovered or refunded within one year.

In mid-February 2021, the central U.S. (from south Texas to North Dakota and the eastern Rocky Mountains) experienced extreme cold temperatures, which increased natural gas demand and caused supply issues due to wellhead freeze-offs, power outages, or other adverse operating conditions upstream of Southwest’s distribution systems. These conditions caused daily natural gas prices to reach unprecedented levels. During this time, Southwest secured natural gas supplies, albeit at substantially higher prices, maintaining service to its customers. The incremental cost for these supplies was approximately $250 million, funded using a 364-day $250 million term loan executed in March 2021 (see Note 8 - Debt). The incremental gas costs were included, for collection from customers, as part of the purchased gas adjustment (“PGA”) mechanisms.

Prepaid and other current assets. Prepaid and other current assets for Southwest and the Company include, among other things, accrued purchased gas costs of $52 million in 2021 and $29 million in 2020, and gas pipe materials and operating supplies of $62.9 million in 2021 and $50 million in 2020 (carried at weighted average cost). Additionally, at the Company, there was $4.5 million in gas pipe materials and operating supplies in 2021 relating to Questar Pipelines, for a total of $67.4 million.

In the third quarter of 2021, the Company and Southwest classified certain assets associated with its previous corporate headquarters as held for sale. As a result, the Company and Southwest reclassified approximately $31 million from Net regulated operations plant to Prepaid and other current assets on their respective Consolidated Balance Sheets during the third quarter of 2021; this was a non-cash item and therefore did not impact the Company’s or Southwest’s respective Consolidated Statements of Cash Flows.

Goodwill. As required by U.S. GAAP, goodwill is assessed for impairment annually, or more frequently, if circumstances indicate impairment to the carrying value of goodwill may have occurred. The goodwill impairment analysis was conducted as of October 1st using a qualitative assessment, as permitted by U.S. GAAP. Management of the Company and Southwest considered its reporting units and segments and determined that they remained consistent between periods presented below, and that no change was necessary with regard to the level at which goodwill is assessed for impairment. The Company and Southwest determined that it is not more likely than not that the fair values of the reporting units were less than their carrying amounts in either 2021 or 2020. Thus, no impairment was recorded in either year.

The Riggs Distler acquisition that was completed in August 2021 (see further discussion in Note 15 - Business Acquisitions) was deemed a stock purchase for tax purposes, and as a result, only pre-acquisition goodwill that was historically tax-deductible by Riggs Distler will continue to be deductible for tax purposes by the Company. The Questar Pipelines acquisition in December 2021 (also included in Note 15 - Business Acquisitions) was considered an asset purchase for tax purposes. As a result, goodwill associated with Questar Pipelines is expected to be tax deductible. Given the Company’s acquisition of Questar Pipelines occurred on December 31, 2021, the Company will assess related goodwill in association with the annual impairment assessment processes starting in 2022. Goodwill in Southwest’s natural gas distribution segment and in all of the Company’s operations, is reflected in their Consolidated Balance Sheets as follows (and as applicable):


(Thousands of dollars)	Natural Gas Distribution		Utility Infrastructure Services		Pipeline and Storage		Total Company
Balance, December 31, 2019	$	10,095	$	332,928	$	—	$	343,023
Foreign currency translation adjustment	—		2,161		—		2,161
Balance, December 31, 2020	10,095		335,089		—		345,184
Additional goodwill from Riggs Distler acquisition	—		449,501		—		449,501
Additional goodwill from Questar Pipelines acquisition	—		—		986,179		986,179
Foreign currency translation adjustment	—		468		—		468
Balance, December 31, 2021	$	10,095	$	785,058	$	986,179	$	1,781,332

Other Current Liabilities. Management recognizes in its balance sheets various liabilities that are expected to be settled through future cash payment within the next twelve months, including certain regulatory liabilities (refer to Note 5 - Regulatory Assets and Liabilities), customary accrued expenses for employee compensation and benefits, and declared but unpaid dividends.

Accumulated Removal Costs. Approved regulatory practices allow Southwest and Questar Pipelines to include in depreciation expense a component intended to recover removal costs associated with regulated operations plant retirements. In accordance with the Securities and Exchange Commission (“SEC”) position on presentation of these amounts, management reclassifies estimated removal costs from Accumulated depreciation to Accumulated removal costs within the liabilities section of the Consolidated Balance Sheets. Management regularly updates the estimated accumulated removal costs as amounts fluctuate between periods depending on the level of replacement work performed (and actual cost experience) compared to the estimated cost of removal in rates.

Gas Operating Revenues. Southwest recognizes revenue when it satisfies its performance by transferring gas to the customer. Natural gas is delivered and “consumed” by the customer simultaneously. Revenues are recorded when customers are billed. Customer billings are substantially based on monthly meter reads and include certain other charges assessed monthly, and are calculated in accordance with applicable tariffs and state and local laws, regulations, and related agreements. An estimate of the margin associated with natural gas service provided, but not yet billed, to residential and commercial customers from the latest meter read date to the end of the reporting period is also recognized as accrued utility revenue. Revenues also include the net impacts of margin tracker/decoupling accruals based on criteria in U.S. GAAP for rate-regulated entities associated with alternative revenue programs. All of Southwest’s service territories have decoupled rate structures, which are designed to eliminate the direct link between volumetric sales and revenue, thereby mitigating the impacts of unusual weather variability and conservation on margin. See Note 3 - Revenue.

Utility Infrastructure Services Revenues. The majority of Centuri contracts are performed under unit-price contracts. Generally, these contracts state prices per unit of installation. Typical installations are accomplished in a few weeks or less. Revenues are recorded as installations are completed. Revenues are recorded for long-term fixed-price contracts in a pattern that reflects the transfer of control of promised goods and services to the customer over time. The amount of revenue recognized on fixed-price contracts is based on costs expended to date relative to anticipated final contract costs. Changes in job performance, job conditions, and final contract settlements are factors that influence management’s assessment of total contract value and the total estimated costs to complete those contracts. Revisions in estimates of costs and earnings during the course of work are

reflected in the accounting period in which the facts requiring revision become known. If a loss on a contract becomes known or is anticipated, the entire amount of the estimated ultimate loss is recognized at that time in the financial statements. Some unit-price contracts contain caps that if encroached, trigger revenue and loss recognition similar to a fixed-price contract model. See Note 3 - Revenue.

Intercompany Transactions. Centuri recognizes revenues generated from contracts with Southwest (see Note 13 - Segment Information). The accounts receivable balance, revenues, and associated profits are included in the consolidated financial statements of the Company and Southwest and were not eliminated during consolidation in accordance with accounting treatment for rate-regulated entities.

Utility Infrastructure Services Expenses. Centuri’s utility infrastructure services expenses in the Consolidated Statements of Income includes payroll expenses, office and equipment rental costs, subcontractor expenses, training, job-related materials, gains and losses on equipment sales, and professional fees.

Net Cost of Gas Sold. Components of net cost of gas sold include natural gas commodity costs (fixed-price and variable-rate), pipeline capacity/transportation costs, and actual settled costs of natural gas derivative instruments, where relevant. Also included are the net impacts of PGA deferrals and recoveries, which by their inclusion, result in net cost of gas sold overall that is comparable to amounts included in billed gas operating revenues. Differences between amounts incurred with suppliers, transmission pipelines, etc. and amounts already included in customer rates, are temporarily deferred in PGA accounts pending inclusion in customer rates.

Operations and Maintenance Expense. Operations and maintenance expense includes Southwest’s operating and maintenance costs associated with serving utility customers and maintaining its distribution and transmission systems, uncollectible customer accounts expense, administrative and general salaries and expense, employee benefits expense excluding relevant non-service cost components, and legal expense (including injuries and damages).

Depreciation and Amortization. Regulated operations plant depreciation is computed on the straight-line remaining life method at composite rates considered sufficient to amortize costs over estimated service lives, including components which compensate for removal costs (net of salvage value), and retirements, as approved by the appropriate regulatory agency. When plant is retired from service, the original cost of plant, including cost of removal, less salvage, is charged to the accumulated provision for depreciation. See also discussion regarding Accumulated Removal Costs above. Other regulatory assets, including acquisition adjustments, are amortized when appropriate, over time periods authorized by regulators. Non-regulated operations, including utility infrastructure services-related property and equipment are depreciated on a straight-line method based on the estimated useful lives of the related assets. Costs and gains related to refunding regulated operations debt and debt issuance expenses are deferred and amortized over the weighted-average lives of the new issues and become a component of interest expense.

Allowance for Funds Used During Construction (“AFUDC”). AFUDC represents the cost of both debt and equity funds used to finance regulated operations plant construction. AFUDC is capitalized as part of the cost of regulated operations plant. The debt portion of AFUDC is reported in the Company’s and Southwest’s Consolidated Statements of Income as an offset to Net interest deductions and the equity portion is reported as Other income. Regulated operations plant construction costs, including AFUDC, are recoverable as part of authorized rates through depreciation when completed projects are placed into operation, and general rate relief is requested and granted. AFUDC, disaggregated by type, included in the Company’s and Southwest’s Consolidated Statements of Income are presented in the table below:


(Thousands of dollars)	2021			2020			2019
AFUDC:
Debt portion	$	1,046		$	3,202		$	4,558
Equity portion	—			4,724			4,161
AFUDC capitalized as part of regulated operations plant	$	1,046		$	7,926		$	8,719
AFUDC rate	0.96		%	5.51		%	5.36		%

Debt and equity AFUDC were impacted in 2021 by the amount of short-term debt outstanding based on the regulatory formula for each component.

Other Income (Deductions). The following table provides the composition of significant items included in Other income (deductions) on the Consolidated Statements of Income:


(Thousands of dollars)	2021		2020		2019
Southwest Gas Corporation – natural gas distribution segment:
Change in COLI policies	$	8,800	$	9,200	$	17,400
Interest income	5,113		4,015		6,356
Equity AFUDC	—		4,724		4,161
Other components of net periodic benefit cost	(14,021)		(20,022)		(15,059)
Miscellaneous income and (expense)	(4,451)		(4,507)		(3,341)
Southwest Gas Corporation – total other income (deductions)	(4,559)		(6,590)		9,517
Utility infrastructure services segment:

Foreign transaction gain (loss)	(22)		(16)		546
Equity in earnings of unconsolidated investment – Western	226		80		439
Miscellaneous income and (expense)	863		(271)		(519)
Centuri – total other income (deductions)	1,067		(207)		466
Corporate and administrative	(7)		8		102
Consolidated Southwest Gas Holdings, Inc. - total other income (deductions)	$	(3,499)	$	(6,789)	$	10,085

Included in the table above is the change in COLI policies (including net death benefits recognized). Current tax regulations provide for tax-free treatment of life insurance (death benefit) proceeds. Therefore, changes in the cash surrender value components of COLI policies, as they progress towards the ultimate death benefits, are also recorded without tax consequences.

Derivatives. In managing its natural gas supply portfolios, Southwest has historically entered into fixed- and variable-price contracts, which qualify as derivatives. Additionally, Southwest previously utilized fixed-for-floating swap contracts (“Swaps”) to supplement its fixed-price contracts. The fixed-price contracts, firm commitments to purchase a fixed amount of gas in the future at a fixed price, qualify for the normal purchases and normal sales exception that is allowed for contracts that are probable of delivery in the normal course of business, and are exempt from fair value reporting. The variable-price contracts qualify as derivative instruments; however, because the contract price is the prevailing price at the future transaction date, no fair value adjustment is required. In consultation with its regulators, management does not currently anticipate entering into new Swaps in the near term; the remaining Swaps matured in October 2020. Southwest does not utilize derivative financial instruments for speculative purposes, nor does it have trading operations.

Previously, Southwest entered into two forward-starting interest rate swaps (“FSIRS”). One of the FSIRS became fully amortized in the third quarter of 2020, with one FSIRS remaining to be amortized in 2022. The settled position for the remaining FSIRS is immaterial and will continue to be amortized from Accumulated other comprehensive income (loss) into interest expense.

Foreign Currency Translation. Foreign currency-denominated assets and liabilities of consolidated subsidiaries are translated into U.S. dollars at exchange rates existing at the respective balance sheet dates. Translation adjustments resulting from fluctuations in exchange rates are recorded as a separate component of accumulated other comprehensive income within stockholders’ equity. Results of operations of foreign subsidiaries are translated using the monthly weighted-average exchange rates during the respective periods. Gains and losses resulting from foreign currency transactions are included in Other income and (expenses) of the Company. Gains and losses resulting from intercompany foreign currency transactions that are of a long-term investment nature are reported in Other comprehensive income, if applicable.

Earnings Per Share. Basic earnings per share (“EPS”) in each period of this report were calculated by dividing net income attributable to Southwest Gas Holdings, Inc. by the weighted-average number of shares during those periods. Diluted EPS includes additional weighted-average common stock equivalents (performance shares and restricted stock units). Unless otherwise noted, the term “Earnings Per Share” refers to Basic EPS. A reconciliation of the denominator used in Basic and Diluted EPS calculations is shown in the following table:


(In thousands)	2021	2020	2019
Weighted average basic shares	59,145	55,998	54,245
Effect of dilutive securities:
Management Incentive Plan shares	—	—	12
Restricted stock units (1)	114	78	55
Weighted average diluted shares	59,259	56,076	54,312

(1) The number of securities granted for 2021, 2020, and 2019 includes 104,000, 69,000, and 46,000 performance shares, respectively, the total of which was derived by assuming that target performance will be achieved during the relevant performance period.

Redeemable Noncontrolling Interests. In connection with the acquisition of Linetec in November 2018, the previous owner retained a 20% equity interest in Linetec, the reduction of which is subject to certain rights based on the passage of time or upon the occurrence of certain triggering events. Additionally, in November 2021, certain members of Riggs Distler management acquired a 1.42% interest in Drum Parent LLC, formerly Drum Parent, Inc., which is subject to certain rights based on the passage of time or upon the occurrence of certain triggering events. See Note 14 - Redeemable Noncontrolling Interests.

Recent Accounting Standards Updates.

Accounting pronouncements adopted in 2021:

In December 2019, the FASB issued ASU 2019-12 “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes.” The update simplifies the accounting for income taxes by removing certain exceptions to the general principles, as well as improving consistent application in Topic 740 by clarifying and amending existing guidance. The Company and Southwest adopted the update in the first quarter of 2021, the impact of which was not material to the consolidated financial statements of the Company or Southwest.

In October 2021, the FASB issued ASU 2021-08 “Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers.” The update amongst other amendments, improves the guidance related to the recognition and measurement of contract assets and liabilities acquired during a business acquisition. The Company and Southwest adopted the update early on a retrospective basis as of January 1, 2021, as permitted, and concluded the impact was not material to the consolidated financial statements of the Company or Southwest. See Note 15 - Business Acquisitions.

Recently issued accounting pronouncements that will be effective in 2022:

In March 2020, the FASB issued ASU 2020-04 “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting.” The update provides optional guidance for a limited time to ease the potential burden in accounting for, or recognizing the effects of, reference rate reform on financial reporting, including when modifying a contract (during the eligibility period covered by the update to the topic) to replace a reference rate affected by reference rate reform. The update applies only to contracts and hedging relationships that reference the London Interbank Offered Rate (“LIBOR”) or another reference rate expected to be discontinued due to reference rate reform. The guidance was eligible to be applied upon issuance on March 12, 2020, and can generally be applied through December 31, 2022, but to date, no further updates have occurred that would extend the optional guidance to the full tenor of LIBOR expiration dates occurring after 2022. Management will monitor the impacts this update might have on the Company’s and Southwest’s consolidated financial statements and disclosures, and will reflect such appropriately, in the event that the optional guidance is elected. See also LIBOR discussion in Note 8 - Debt.

In August 2020, the FASB issued ASU 2020-06 “Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging— Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity.” The update, amongst other amendments, improves the guidance related to the disclosures and earnings per share for convertible instruments and contracts in an entity’s own equity. The update is effective for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years; early adoption was permitted. Management is evaluating the impacts this update might have on the Company’s consolidated financial statements and disclosures.

Subsequent Events. Management monitors events occurring after the balance sheet date and prior to the issuance of the financial statements to determine the impacts, if any, of events on the financial statements to be issued or disclosures to be made, and has reflected them where appropriate.

Regulated Operations Plant and Leases

12 Months Ended

Dec. 31, 2021

Regulated Operations [Abstract]

Regulated Operations Plant and Leases

Note 2 - Regulated Operations Plant and Leases

Net Regulated Operations Plant

Major classes of regulated operations plant and their respective balances as of December 31, 2021 and 2020 were as follows:


	December 31,				December 31,
(Thousands of dollars)	2021		2020		2021		2020
	Southwest Gas Holdings, Inc.*				Southwest Gas Corporation
Gas plant:
Storage	$	437,793	$	101,203	$	103,874	$	101,203
Transmission	1,917,529		400,657		397,590		400,657
Distribution	7,506,489		7,078,656		7,506,489		7,078,656
General	530,346		515,879		496,643		515,879
Software and software-related intangibles	380,372		270,883		380,372		270,883
Other	17,161		16,722		16,607		16,722
	10,789,690		8,384,000		8,901,575		8,384,000
Less: accumulated depreciation and amortization	(3,397,736)		(2,419,348)		(2,538,508)		(2,419,348)
Construction work in progress	202,068		211,429		183,485		211,429
Net regulated operations plant	$	7,594,022	$	6,176,081	$	6,546,552	$	6,176,081

*Southwest Gas Holdings, Inc. includes the regulated operations plant associated with the Questar Pipelines acquisition.

Regulated operations plant depreciation is computed on the straight-line remaining life method at composite rates considered sufficient to amortize costs over estimated service lives, including components which are intended to compensate for removal costs (net of salvage value), and retirements, based on the processes of regulatory proceedings and related regulatory commission approvals and/or mandates. In 2021, 2020, and 2019, annual regulated operations depreciation and amortization expense in regard to Southwest averaged 2.7% of the original cost of depreciable and amortizable property. Transmission and distribution plant are associated with the core natural gas delivery infrastructure, and combined, constitute the majority of gas plant. Annual regulated operations depreciation expense for Southwest averaged approximately 2.3% of the original cost of depreciable transmission and distribution plant during the period 2019 through 2021. Questar Pipelines plant was subject to the business acquisition on December 31, 2021.

Depreciation and amortization expense on gas plant, including intangibles, was as follows:


(Thousands of dollars)	2021		2020		2019
Depreciation and amortization expense	$	230,245	$	215,636	$	197,358

Included in the figures above is amortization of regulated operations intangibles of $17.7 million, $13.7 million, and $13.2 million for the years ended December 31, 2021, 2020, and 2019, respectively. The amounts above exclude regulatory asset and liability amortization.

Leases

Determinations are made as to whether an arrangement is a lease at inception. ROU assets represent the right to use an underlying asset for the lease term; lease liabilities represent obligations to make lease payments arising from the lease. Operating lease ROU assets and lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. When leases do not provide an implicit interest rate, an incremental borrowing rate based on information available at commencement is used in determining the present value of lease payments; an implicit rate, if readily determinable, is used. Lease terms utilized in the computations may include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. When lease agreements include non-lease components, they are included with the lease component and accounted for as a single component, for all asset classes.

Southwest’s leases are comprised primarily of operating leases of buildings, land, and equipment. Southwest has no finance leases and no significant short-term leases. Southwest’s leases have a remaining term of up to 5 years, some of which include optional renewal periods. Southwest is currently not a lessor in any significant lease arrangements.

Centuri has operating and finance leases for corporate and field offices, construction equipment, and transportation vehicles. Centuri is currently not a lessor in any significant lease arrangements. Centuri’s leases have remaining lease terms of up to 17 years. Some of these include options to extend the leases, generally for optional terms of up to 5 years, and some include options to terminate the leases within 1 year. Centuri’s equipment leases may include variable payment terms in addition to the fixed lease payments if machinery is used in excess of the standard work periods. These variable payments are not probable of occurring under the current operating environment and have not been included in consideration of lease payments. During 2021, the presentation of short-term lease cost changed to include all short-term costs associated with leases with a term of less than one month as compared to the historical presentation of only including short-term lease costs for leases with a duration of over one month and less than one year. The lease costs associated with leases with terms of less than one month were $66.4 million and $67 million for the years ended December 31, 2020 and 2019, respectively. As of December 31, 2021, Centuri executed lease agreements that had not yet commenced. These lease agreements primarily relate to real estate leases that have terms ranging from January 2022 through December 2032. Total future lease payments over the lease terms are approximately $1.7 million.

There were no significant operating or finance leases acquired on December 31, 2021 as part of the Questar Pipelines acquisition.

The components of lease expense were as follows:


(Thousands of dollars)	2021		2020		2019
Southwest:
Operating lease cost	$	1,021	$	1,251	$	1,531

Centuri:
Operating lease cost	15,279		14,294		12,235

Finance lease cost:
Amortization of ROU assets	2,138		140		137
Interest on lease liabilities	278		37		34
Total finance lease cost	2,416		177		171
Short-term lease cost	103,800		19,806		16,217
Total lease cost - Southwest Gas Holdings, Inc.	$	122,516	$	35,528	$	30,154

Supplemental cash flow information related to leases for the years ended December 31, 2021, 2020 and 2019 was as follows:


	2021
(Thousands of dollars)	Southwest		Centuri		Total
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	744	$	14,669	$	15,413
Operating cash flows from finance leases	—		278		278
Financing cash flows from finance leases	—		3,547		3,547

ROU assets obtained in exchange for lease obligations:
Operating leases	$	609	$	11,597	$	12,206
Finance leases	—		3,332		3,332


	2020
(Thousands of dollars)	Southwest		Centuri		Total
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	766	$	12,889	$	13,655
Operating cash flows from finance leases	—		36		36
Financing cash flows from finance leases	—		199		199

ROU assets obtained in exchange for lease obligations:
Operating leases	$	1,547	$	19,372	$	20,919
Finance leases	—		361		361


	2019
(Thousands of dollars)	Southwest		Centuri		Total
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	1,278	$	11,166	$	12,444
Operating cash flows from finance leases	—		33		33
Financing cash flows from finance leases	—		212		212

ROU assets obtained in exchange for lease obligations:
Operating leases	$	862	$	23,825	$	24,687
Finance leases	—		13,839		13,839

Supplemental information related to leases, including location in the Consolidated Balance Sheets, is as follows:


(Thousands of dollars)	December 31,
	2021			2020
Southwest:
Operating leases:
Net regulated operations plant	$	2,072		$	2,195

Other current liabilities	$	607		$	656
Other deferred credits and other long-term liabilities	1,500			1,586
Total operating lease liabilities	$	2,107		$	2,242

Weighted average remaining lease term (in years)	4.22			4.24
Weighted average discount rate	4.90		%	4.49		%

Centuri:
Operating leases:
Other property and investments	$	80,638		$	81,010

Other current liabilities	$	12,185		$	10,032
Other deferred credits and other long-term liabilities	72,930			75,247
Total operating lease liabilities	$	85,115		$	85,279

Finance leases:
Other property and investments	$	30,705		$	752

Other current liabilities	$	8,858		$	202
Other deferred credits and other long-term liabilities	20,585			490
Total finance lease liabilities	$	29,443		$	692

Weighted average remaining lease term (in years)
Operating leases	7.57			10.08
Finance leases	3.92			2.12

Weighted average discount rate
Operating leases	3.95		%	4.05		%
Finance leases	2.58		%	5.55		%

The following are schedules of maturities of lease liabilities as of December 31, 2021:


(Thousands of dollars)	Operating Leases
Southwest:
2022	$	639
2023	522
2024	499
2025	483
2026	220
Thereafter	—
Total lease payments	2,363
Less imputed interest	256
Total	$	2,107


(Thousands of dollars)	Operating Leases		Finance Leases
Centuri:
2022	$	15,200	$	9,494
2023	13,402		7,940
2024	11,321		6,476
2025	9,228		3,987
2026	7,878		2,108
Thereafter	45,529		1,008
Total lease payments	102,558		31,013
Less imputed interest	17,443		1,570
Total	$	85,115	$	29,443

Revenue

12 Months Ended

Dec. 31, 2021

Revenue from Contract with Customer [Abstract]

Revenue

Note 3 - Revenue

The following information about the Company’s revenues is presented by segment. Southwest encompasses the natural gas distribution segment and Centuri encompasses the utility infrastructure services segment. The pipeline and storage segment related to Questar Pipelines was acquired on the last day of 2021.

Natural Gas Distribution Segment:

Southwest recognizes revenue when it satisfies its performance by transferring gas to the customer. Revenues also include the net impacts of margin tracker/decoupling accruals based on criteria in U.S. GAAP for rate-regulated entities associated with alternative revenue programs. Revenues from customer arrangements and from alternative revenue programs are described below.

Southwest acts as an agent for state and local taxing authorities in the collection and remittance of a variety of taxes, including sales and use taxes and surcharges. These taxes are not included in Gas operating revenues. Management uses the net classification method to report taxes collected from customers to be remitted to governmental authorities.

Southwest generally offers two types of services to its customers: tariff sales and transportation–only service. Tariff sales encompass sales to many types of customers (primarily residential) under various rate schedules, subject to cost-of-service ratemaking, which is based on the rate-regulation of state commissions and the FERC. Southwest provides both the commodity and the related distribution service to nearly all of its approximate 2.2 million customers, and only several hundred customers (who are eligible to secure their own gas) subscribe to transportation-only service. Also, only a few hundred customers have contracts with stated periods. Natural gas is delivered and consumed by the customer simultaneously. The provision of service is represented by the turn of the meter dial and is the primary representation of the satisfaction of performance obligations of Southwest. The amount billable via regulated rates (both volumetric and fixed monthly rates as part of rate design) corresponds to the value to the customer, and management believes that the amount billable (amount Southwest has the right to invoice) is appropriate to utilize for purposes of recognizing revenue. Estimated amounts remaining unbilled since the last meter read date are restricted from being billed due only to the passage of time and therefore are also recognized for service provided through the balance sheet date. While natural gas service is typically recurring, there is generally not a contract term for utility service. Therefore, the contract term is not generally viewed to extend beyond the service provided to date, and customers can generally terminate service at will.

Transportation-only service is also governed by tariff rate provisions. Transportation-only service is generally only available to very large customers under requirements of Southwest’s various tariffs. With this service, customers secure their own gas supply and Southwest provides transportation services to move the customer-supplied gas to the intended location. Southwest concluded that transportation/transmission service is suitable to an “over time” recognition model. Rate structures under Southwest’s regulation for transportation customers include a combination of volumetric charges and monthly “fixed” charges (including charges commonly referred to as capacity charges, demand charges, or reservation charges) as part of the rate design of regulated jurisdictions. These types of fixed charges represent a separate performance obligation associated with standing ready over the period of the month to deliver quantities of gas, regardless of whether the customer takes delivery of any quantity of gas. The performance obligations under these circumstances are satisfied over the course of the month under an output measure of progress based on time, which correlates to the period for which the charges are eligible to be invoiced.

Under its regulation, Southwest enters into negotiated rate contracts for those customers located in proximity to another pipeline, which pose a threat of bypassing its distribution system. Southwest may also enter into similar contracts for customers otherwise able to satisfy their energy needs by means of alternative fuel to natural gas. Less than two dozen customers are party to contracts with rate components subject to negotiation. Many rate provisions and terms of service for these less common types of contracts are also subject to regulatory oversight and tariff provisions. The performance obligations for these customers are satisfied similarly to those for other customers by means of transporting/delivering natural gas to the customer. Many or most of the rate components, and structures, for these types of customers are the same as those for similar customers without negotiated rate components; and the negotiated rates are within the parameters of the tariff guidelines. Furthermore, while some of these contracts include contract periods extending over time, including multiple years, as amounts billable under the contract are based on rates in effect for the customer for service provided to date, no significant financing component is deemed to exist.

As indicated above, revenues also include the net impacts of margin tracker/decoupling accruals. All of Southwest’s service territories have decoupled rate structures (also referred to as alternative revenue programs) that are designed to eliminate the direct link between volumetric sales and revenue, thereby mitigating the impacts of unusual weather variability and conservation on margin. The primary alternative revenue programs involve permissible adjustments for differences between stated tariff benchmarks and amounts billed through revenue from contracts with customers via existing rates. Such adjustments are recognized monthly in revenue and in the associated regulatory asset/liability accounts in advance of rate adjustments intended to collect or return amounts recognized. Revenues recognized for the adjustment to the benchmarks noted are required to be presented separately from revenues from contracts with customers, and as such, are provided below and identified as related to alternative revenue programs (which excludes recoveries from customers).

Gas operating revenues on the Consolidated Statements of Income of both the Company and Southwest include revenue from contracts with customers, which is shown below disaggregated by customer type, and various categories of revenue:


	December 31,
(Thousands of dollars)	2021		2020		2019
Residential	$	1,035,612	$	958,520	$	972,788
Small commercial	270,214		221,541		249,117
Large commercial	57,371		44,633		48,935
Industrial/other	42,313		26,242		22,074
Transportation	92,240		88,215		92,380
Revenue from contracts with customers	1,497,750		1,339,151		1,385,294
Alternative revenue program deferrals	13,181		12,140		(25,112)
Other revenues (a)	10,859		(706)		8,757
Total Gas operating revenues	$	1,521,790	$	1,350,585	$	1,368,939

(a) Amounts include late fees and other miscellaneous revenues, and may also include the impact of certain regulatory mechanisms, such as cost-of-service components in current customer rates that are expected to be returned to customers in future periods. Also includes the impacts of a temporary moratorium on late fees and disconnection for nonpayment during the COVID-19 pandemic and impacts between periods, once lifted; 2020 and 2019 include amounts related to tax reform savings reserves/adjustments.

Utility Infrastructure Services Segment:

The majority of Centuri contracts are performed under unit-price contracts. Generally, these contracts state prices per unit of installation. Typical installations are accomplished in a few weeks or less. Revenues are recorded as installations are completed. Revenues are recorded for long-term fixed-price contracts in a pattern that reflects the transfer of control of promised goods and services to the customer over time. The amount of revenue recognized on fixed-price contracts is based on costs expended to date relative to anticipated final contract costs (a method of recognition based on inputs). Some unit-price contracts contain caps that if encroached, trigger revenue and loss recognition similar to a fixed-price contract model.

Centuri is required to collect taxes imposed by various governmental agencies on the work performed for its customers. These taxes are not included in Utility infrastructure services revenues. Management uses the net classification method to report taxes collected from customers to be remitted to governmental authorities.

Centuri derives revenue from the installation, replacement, repair, and maintenance of energy distribution systems. Centuri has operations in the U.S. and Canada. The primary focus of Centuri operations is replacement of natural gas distribution pipe and electric service lines, as well as new infrastructure installations. In addition, Centuri performs certain industrial construction activities for various customers and industries. Centuri has two types of agreements with its customers: master services agreements (“MSAs”) and bid contracts. Most of Centuri’s customers supply many of their own materials in order for Centuri to complete its work under the contracts.

An MSA identifies most of the terms describing each party’s rights and obligations that will govern future work authorizations. An MSA is often effective for multiple years. A work authorization is issued by the customer to describe the location, timing, and any additional information necessary to complete the work for the customer. The combination of the MSA and the work authorization determines when a contract exists and revenue recognition may begin. Each work authorization is generally a single performance obligation as Centuri is performing a significant integration service.

A bid contract is typically a one-time agreement for a specific project that has all necessary terms defining each party’s rights and obligations. Each bid contract is evaluated for revenue recognition individually. Control of assets created under bid contracts generally passes to the customer over time. Bid contracts often have a single performance obligation as Centuri is providing a significant integration service.

Centuri’s MSA and bid contracts are characterized as either fixed-price contracts or unit-price contracts for revenue recognition purposes. The cost-to-cost input method is used to measure progress towards the satisfaction of a performance obligation for fixed-price contracts. Input methods result in the recognition of revenue based on the entity’s expended effort toward satisfaction of the performance obligation relative to the total expected effort to satisfy it in full. For unit-price contracts, an output method is used to measure progress towards satisfaction of a performance obligation (based on the completion of each unit that is required under the contract).

Actual revenues and project costs can vary, sometimes substantially, from previous estimates due to changes in a variety of factors, including unforeseen circumstances. These factors, along with other risks inherent in performing fixed-price contracts may cause actual revenues and gross profit for a project to differ from previous estimates, and could result in reduced profitability or losses on projects. Changes in these factors may result in revisions to costs and earnings, the impacts for which are recognized in the period in which the changes are identified. Once identified, these types of conditions continue to be evaluated for each project throughout the project term, and ongoing revisions in management’s estimates of contract value, cost, and profit are recognized as necessary in the period determined.

Centuri categorizes work performed under MSAs and bid contracts into three primary service types: gas construction, electrical construction, and other construction. Gas construction includes work involving previously existing gas pipelines and the installation of new pipelines or service lines. Electrical construction includes work involving installation and maintenance of transmission and distribution lines, including storm restoration services. Other construction includes all other work and can include industrial and water utility services.

Contracts can have compensation/consideration that is variable. For MSAs, variable consideration is evaluated at the customer level as the terms creating variability in pricing are included within the MSA and are not specific to a work authorization. For multi-year MSAs, variable consideration items are typically determined for each year of the contract and not for the full contract term. For bid contracts, variable consideration is evaluated at the individual contract level. The expected value method or most likely amount method is used based on the nature of the variable consideration. Types of variable consideration include liquidated damages, delay penalties, performance incentives, safety bonuses, payment discounts, and volume rebates. Centuri will typically estimate variable consideration and adjust financial information, as necessary.

Change orders involve the modification in scope, price, or both to the current contract, requiring approval by both parties. The existing terms of the contract continue to be accounted for under the current contract until such time as a change order is approved. Once approved, the change order is either treated as a separate contract or as part of the existing contract, as appropriate, under the circumstances. When the scope is agreed upon in the change order but not the price, Centuri estimates the change to the transaction price.

The following tables display Centuri’s revenue from contracts with customers disaggregated by service type and contract type:


	December 31,
(Thousands of dollars)	2021		2020		2019
Service Types:
Gas infrastructure services	$	1,302,340	$	1,261,160	$	1,238,974
Electric power infrastructure services	525,202		411,826		247,717
Other	331,119		275,302		264,287
Total Utility infrastructure services revenues	$	2,158,661	$	1,948,288	$	1,750,978


	December 31,
(Thousands of dollars)	2021		2020		2019
Contract Types:
Master services agreement	$	1,652,978	$	1,490,009	$	1,383,377
Bid contract	505,683		458,279		367,601
Total Utility infrastructure services revenues	$	2,158,661	$	1,948,288	$	1,750,978

Unit price contracts	$	1,369,082	$	1,356,640	$	1,380,256
Fixed price contracts	267,742		157,701		112,924
Time and materials contracts	521,837		433,947		257,798
Total Utility infrastructure services revenues	$	2,158,661	$	1,948,288	$	1,750,978

The following table provides information about contracts receivable and revenue earned on contracts in progress in excess of billings (contract assets), both of which are included within Accounts receivable, net of allowances, and provides information about amounts billed in excess of revenue earned on contracts (contract liabilities), which are included in Other current liabilities as of December 31, 2021 and 2020 on the Company’s Consolidated Balance Sheets:


	December 31,
(Thousands of dollars)	2021		2020
Contracts receivable, net	$	296,005	$	278,316
Revenue earned on contracts in progress in excess of billings	214,774		96,996
Amounts billed in excess of revenue earned on contracts	11,860		4,507

The revenue earned on contracts in progress in excess of billings (contract asset) primarily relates to Centuri’s rights to consideration for work completed but not billed and/or approved at the reporting date. These contract assets are transferred to contracts receivable when the rights become unconditional. These contract assets are recoverable from Centuri’s customers based upon various measures of performance, including achievement of certain milestones, completion of specified units or completion of a contract. In addition, many of Centuri’s time and materials arrangements are billed in arrears pursuant to contract terms that are standard within the industry, resulting in contract assets and/or unbilled receivables being recorded, as revenue is recognized in advance of billings. Due to the lag in invoicing associated with contractual provisions (or other economic or market conditions that may impact a customer’s business), Centuri’s ability to bill and subsequently collect amounts due may be impacted. These changes may result in the need to record an estimated valuation allowance to adjust contract asset balances to their net realizable value. During 2021, in connection with the acquisition of Riggs Distler, Centuri recorded $47.5 million of contract assets.

The amounts billed in excess of revenue earned (contract liability) primarily relate to the advance consideration received from customers for which work has not yet been completed. This contract liability balance decreased subsequent to December 31, 2020 due to revenue recognized of approximately $4.5 million that was included in this balance as of January 1, 2021, after which time it became earned and the balance was reduced. This decrease was offset by increases due to cash received, net of revenue recognized during the period related to contracts that commenced during the period, as well as $12.7 million of contract liabilities assumed related to the acquisition of Riggs Distler. See Note 15 - Business Acquisitions for additional information.

For contracts that have an original duration of one year or less, Centuri does not consider/compute an interest component based on the time value of money. Further, because of the short duration of these contracts, the Company has not disclosed the transaction price for the remaining performance obligations as of the end of each reporting period or when the Company expects to recognize the revenue.

As of December 31, 2021, Centuri has 26 contracts with an original duration of more than one year. The aggregate amount of the transaction price allocated to the unsatisfied performance obligations of these contracts as of December 31, 2021 was $105.3 million. Centuri expects to recognize the remaining performance obligations over approximately the next two years; however, the timing of that recognition is largely within the control of the customer, including when the necessary equipment and materials required to complete the work will be provided by the customer.

Utility infrastructure services contracts receivable consists of the following:


	December 31,
(Thousands of dollars)	2021		2020
Billed on completed contracts and contracts in progress	$	292,770	$	273,778
Other receivables	3,492		6,692
Contracts receivable, gross	296,262		280,470
Allowance for doubtful accounts	(257)		(2,154)
Contracts receivable, net	$	296,005	$	278,316

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

+ Details

Receivables and Related Allowances

12 Months Ended

Dec. 31, 2021

Receivables [Abstract]

Receivables and Related Allowances

Note 4 - Receivables and Related Allowances

Business activity with respect to natural gas utility operations is conducted with customers located within the three-state region of Arizona, Nevada, and California. Southwest’s accounts receivable are short-term in nature, with billing due dates customarily not extending beyond one month, with customers’ credit worthiness assessed upon account creation by evaluation of other utility service or their credit file, and related payment history. Although Southwest seeks generally to minimize its credit risk related to utility operations by requiring security deposits from new customers, imposing late fees, and actively pursuing collection on overdue accounts, some accounts are ultimately not collected. Customer accounts are subject to collection procedures that vary by jurisdiction (late fee assessment, notice requirements for disconnection of service, and procedures for actual disconnection and/or reestablishment of service). After disconnection of service, accounts are customarily written off approximately two months after disconnection if the account remains inactive. Dependent upon the jurisdiction, reestablishment of service requires both payment of previously unpaid balances and additional deposit requirements. Provisions for uncollectible accounts are recorded monthly based on experience, consideration of current and expected future conditions, customer and rate composition, and write-off processes. They are included in the ratemaking process as a cost of service. The Nevada jurisdictions have a regulatory mechanism associated with the gas-cost-related portion of uncollectible accounts. Such amounts are deferred and collected through a surcharge in the ratemaking process. Southwest lifted the moratorium on disconnection of natural gas service for non-payment in Arizona and Nevada in September 2021, which was initiated (at the same time as a moratorium on late fees) in March 2020 in response to the COVID-19 pandemic. The moratorium on disconnection in California ended in November 2021. Southwest recommenced assessing late fees on past-due balances in Arizona and Nevada in April 2021, and in California in August 2021. Southwest is actively working with customers experiencing financial hardship by means of flexible payment options, partnering with assistance agencies and participating in state funded arrearage payment assistance programs. Management continues to monitor expected credit losses in light of the impact of COVID-19. The allowance as of December 31, 2021 reflects the expected impact from the pandemic on balances as of that date, including consideration of customers’ current and future ability to pay those amounts that are due.

MountainWest’s accounts receivable are also short-term with billing due dates customarily not extending beyond one month. Accounts receivable acquired in the Questar Pipelines acquisition were recorded at their estimated realizable value on December 31, 2021. See Note 15 - Business Acquisitions for additional information.

Utility infrastructure services accounts receivable are recorded at face amounts less an allowance for doubtful accounts. Centuri’s customers are generally investment-grade gas and electric utility companies for which Centuri has historically recognized an insignificant amount of write-offs. Centuri’s accounts receivable balances carry standard payment terms of up to 60 days. Centuri maintains an allowance that is estimated based on historical collection experience, current and estimated future economic and market conditions, and a review of the current status of each customer's accounts receivable balance. Account balances are monitored at least monthly, and are charged off against the allowance when management determines it is probable the balance will not be recovered. Centuri has not been significantly impacted, nor does it anticipate it will experience significant difficulty in collecting amounts due, given the nature of its customers, as a result of the current environment surrounding COVID-19.

The table below contains information about Southwest’s gas utility customer accounts receivable balance (net of allowance) at December 31, 2021 and 2020, and the percentage of customers in each of the three states, which was consistent with the prior year.


	December 31,
(Thousands of dollars)	2021		2020
Gas utility customer accounts receivable balance	$	169,114	$	145,108

The following table represents Southwest customers by state at December 31, 2021:


Percent of customers by state:
Arizona	53	%
Nevada	37	%
California	10	%

Southwest activity in the allowance account for uncollectibles is summarized as follows:


(Thousands of dollars)	Allowance for Uncollectibles
Balance, December 31, 2018	$	2,168
Additions charged to expense	3,507
Accounts written off, less recoveries	(3,580)
Balance, December 31, 2019	2,095
Additions charged to expense	4,693
Accounts written off, less recoveries	(2,454)
Balance, December 31, 2020	4,334
Additions charged to expense	5,415
Accounts written off, less recoveries	(6,490)
Balance, December 31, 2021	$	3,259

At December 31, 2021, the utility infrastructure services segment (Centuri) had $510.8 million in combined customer accounts and contracts receivable. Both the allowance for uncollectibles and write-offs related to Centuri customers have been insignificant and are not reflected in the table above.

Regulatory Assets and Liabilities

12 Months Ended

Dec. 31, 2021

Regulated Operations [Abstract]

Regulatory Assets and Liabilities

Note 5 - Regulatory Assets and Liabilities

Southwest is subject to the regulation of the Arizona Corporation Commission (“ACC”), the Public Utilities Commission of Nevada (“PUCN”), the California Public Utilities Commission (“CPUC”), and the FERC. Questar Pipelines is subject to the regulation of the FERC. Accounting policies of both entities conform to U.S. GAAP applicable to rate-regulated entities and reflect the effects of the ratemaking process. Accounting treatment for rate-regulated entities allows for deferral as regulatory assets, costs that otherwise would be expensed, if it is probable that future recovery from customers will occur. If rate recovery is no longer probable, due to competition or the actions of regulators, the related regulatory asset is required to be written off. Regulatory liabilities are recorded if it is probable that revenues will be reduced for amounts that will be refunded to customers through the ratemaking process. Management records regulatory assets and liabilities based on decisions of the commissions noted above, including the issuance of regulatory orders and precedents established by these commissions. The regulated operations have generally been successful in seeking recovery of regulatory assets, and regularly file rate cases or other administrative filings in the various jurisdictions, in some cases, to establish the basis for recovering regulatory assets reflected in accounting records.

The following table represents existing regulatory assets and liabilities:


	December 31,
	2021		2020		2021		2020
(Thousands of dollars)	Southwest Gas Holdings*				Southwest Gas Corporation
Regulatory assets:
Accrued pension and other postretirement benefit costs (1)	$	339,356	$	427,550	$	339,356	$	427,550

Deferred purchased gas costs (2)	291,145		2,053		291,145		2,053
Settled interest rate hedges (3)	31,278		—		—		—
Accrued purchased gas costs (4)	51,631		29,000		51,631		29,000
Unamortized premium on reacquired debt (5)	16,283		17,124		16,283		17,124
Accrued absence time (9)	16,975		15,565		16,975		15,565
Margin, interest- and tax-tracking (10)	22,709		4,759		22,709		4,759
Other (12)	62,233		45,596		60,798		45,596
	831,610		541,647		798,897		541,647
Regulatory liabilities:
Deferred purchased gas costs (2)	(5,736)		(54,636)		—		(54,636)
Accumulated removal costs (6)	(482,558)		(404,000)		(424,000)		(404,000)

Unamortized gain on reacquired debt (7)	(7,108)		(7,644)		(7,108)		(7,644)
Regulatory excess deferred/other taxes and gross-up (8)	(511,567)		(461,023)		(446,333)		(461,023)
Margin, interest- and property tax-tracking (10)	(8,523)		(17,132)		(8,523)		(17,132)
Unrecognized other postretirement benefit costs (11)	(17,815)		—		—		—
Other (12)	(10,321)		(3,503)		(8,573)		(3,503)
Net regulatory liabilities	$	(212,018)	$	(406,291)	$	(95,640)	$	(406,291)

*Southwest Gas Holdings, Inc. includes the regulatory assets and liabilities acquired as part of the Questar acquisition.

(1)Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovery period is greater than five years. (See Note 11 - Pension and Other Postretirement Benefits).

(2)Balance recovered or refunded on an ongoing basis with interest.

(3)Reflects Questar Pipelines interest rate cash flow hedges entered into in association with the issuance of the $180 million principal balance 4.875% unsecured senior notes due in 2041 that are amortized to interest expense over the life of this debt instrument. The current portion is included in Prepaid and other current assets and the long-term portion is included in Deferred charges and other assets on the Company's December 31, 2021 Consolidated Balance Sheet.

(4)Included in Prepaid and other current assets on the Consolidated Balance Sheets. Balance recovered or refunded on an ongoing basis.

(5)Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovered over life of debt instruments.

(6)Included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets. In 2021, substantially all incremental amounts relating to Questar Pipelines is also included in Other deferred credits and other long-term liabilities, except $2 million which is included in Other current liabilities on the Company’s Consolidated Balance Sheet.

(7)Included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets. Amortized over life of debt instruments.

(8)Includes remeasurement/reduction of the net accumulated deferred income tax liability from U.S. tax reform. The reduction (excess accumulated deferred taxes, or “EADIT”) became a regulatory liability with tax gross-up. EADIT reduces rate base, and is expected to be returned to utility customers in accordance with IRS and regulatory requirements. Included generally, in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets, except for $29 million in 2021 which is in Other current liabilities. Amount also includes difference in current taxes required to be returned to customers and a separate $2.6 million gross-up related to contributions in aid of construction.

(9)Regulatory recovery occurs on a one-year lag basis through the labor loading process. Included in Prepaid and other current assets on the Consolidated Balance Sheets.

(10)Margin tracking/decoupling mechanisms are alternative revenue programs; revenue associated with under-collections (for the difference between authorized margin levels and amounts billed to customers through rates currently) is recognized as revenue so long as recovery is expected to take place within 24 months. Total category asset balances are included in Prepaid and other current assets and Deferred charges and other assets on the Consolidated Balance Sheets. Total category liability balances are included in Other current liabilities and Other deferred credits and other long-term liabilities.

(11)Reflects a regulatory liability for Questar Pipelines for the collection of postretirement benefit costs allowed in rates in excess of expenses incurred. Included in Other deferred credits and other long-term liabilities on the Company’s December 31, 2021 Consolidated Balance Sheet.

(12)The following tables detail the components of Other regulatory assets and liabilities. Other regulatory assets are included in either Prepaid and other current assets or Deferred charges and other assets on the Consolidated Balance Sheets (as indicated). Recovery periods vary. Other regulatory liabilities are included in either Other current liabilities or Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets (as indicated).


	December 31,
	2021		2020		2021		2020
(Thousands of dollars)	Southwest Gas Holdings				Southwest Gas Corporation
Other Regulatory Assets:
State mandated public purpose programs (including low income and conservation programs) (a) (e)	$	15,239	$	11,527	$	15,239	$	11,527
Infrastructure replacement programs and similar (b) (e)	6,545		7,731		6,545		7,731
Environmental compliance programs (c) (e)	6,807		5,235		6,807		5,235
Pension tracking mechanism (b)	10,281		3,075		10,281		3,075
Other (d)	23,361		18,028		21,926		18,028
	$	62,233	$	45,596	$	60,798	$	45,596

a)Included in Prepaid and other current assets on the Consolidated Balance Sheets.

b)Included in Deferred charges and other assets on the Consolidated Balance Sheets.

c)In 2021, approximately $5.8 million of these balances included in Prepaid and other current assets and $1 million included in Deferred charges and other assets on the Consolidated Balance Sheets. In 2020, approximately $4.2 million included in Prepaid and other current assets and $998,000 included in Deferred charges and other assets on the Consolidated Balance Sheets.

d)In 2021, for Southwest Gas Corporation, $6.7 million included in Prepaid and other current assets and $15.2 million included in Deferred charges and other assets on the Consolidated Balance Sheets. For the Company in 2021, $7.7 million included in Prepaid and other current assets and $15.6 million included in Deferred charges and other assets on the Consolidated Balance Sheets. In 2020, $3.6 million included in Prepaid and other current assets and $14.4 million included in Deferred charges and other assets on the Consolidated Balance Sheets.

e)Balance recovered or refunded on an ongoing basis, generally with interest.


	December 31,
	2021		2020		2021		2020
(Thousands of dollars)	Southwest Gas Holdings				Southwest Gas Corporation
Other Regulatory Liabilities:
State mandated public purpose programs (including low income and conservation programs) (a) (c)	$	(1,886)	$	(834)	$	(1,886)	$	(834)
Environmental compliance programs (c) (d)	(4,182)		(405)		(4,182)		(405)

Other (b) (c)	(4,253)		(2,264)		(2,505)		(2,264)
	$	(10,321)	$	(3,503)	$	(8,573)	$	(3,503)

a)Included in Other current liabilities on the Consolidated Balance Sheets.

b)Included in Other deferred credits and other long-term liabilities, except $13,000 which is included included in Other current liabilities on the Consolidated Balance Sheets.

c)Balance typically recovered or refunded on an ongoing basis, generally with interest.

d)In 2021 and 2020, included in Other current liabilities on the Consolidated Balance Sheets.

Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI")

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI")

Note 6 - Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI")

The following information provides insight into amounts impacting the Company’s Other comprehensive income (loss), both before and after-tax impacts, within the Consolidated Statements of Comprehensive Income, which also impact Accumulated other comprehensive income (“AOCI”) in the Consolidated Balance Sheets and the Consolidated Statements of Equity.

Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss)


	Year Ended December 31,
	2021						2020						2019
(Thousands of dollars)	Before- Tax Amount		Tax (Expense) or Benefit (1)		Net-of- Tax Amount		Before- Tax Amount		Tax (Expense) or Benefit (1)		Net-of- Tax Amount		Before- Tax Amount		Tax (Expense) or Benefit (1)		Net-of- Tax Amount
Defined benefit pension plans:
Net actuarial gain/(loss)	$	59,176	$	(14,202)	$	44,974	$	(57,539)	$	13,809	$	(43,730)	$	(71,087)	$	17,061	$	(54,026)
Amortization of prior service cost	959		(230)		729		1,155		(277)		878		1,271		(305)		966
Amortization of net actuarial (gain)/loss	44,597		(10,703)		33,894		37,830		(9,079)		28,751		23,376		(5,610)		17,766
Prior service cost	—		—		—		—		—		—		(1,878)		452		(1,426)
Regulatory adjustment	(88,194)		21,167		(67,027)		7,435		(1,785)		5,650		36,944		(8,867)		28,077
Pension plans other comprehensive income (loss)	16,538		(3,968)		12,570		(11,119)		2,668		(8,451)		(11,374)		2,731		(8,643)
FSIRS (designated hedging activities):
Amounts reclassified into net income	2,174		(522)		1,652		3,247		(780)		2,467		3,344		(803)		2,541
FSIRS other comprehensive income (loss)	2,174		(522)		1,652		3,247		(780)		2,467		3,344		(803)		2,541
Total other comprehensive income (loss) –Southwest Gas Corporation	18,712		(4,490)		14,222		(7,872)		1,888		(5,984)		(8,030)		1,928		(6,102)
Foreign currency translation adjustments:
Translation adjustments	20		—		20		1,713		—		1,713		2,038		—		2,038
Foreign currency other comprehensive income (loss)	20		—		20		1,713		—		1,713		2,038		—		2,038
Total other comprehensive income (loss) – Southwest Gas Holdings, Inc.	$	18,732	$	(4,490)	$	14,242	$	(6,159)	$	1,888	$	(4,271)	$	(5,992)	$	1,928	$	(4,064)

(1) Tax amounts are calculated using a 24% rate. With regard to foreign currency translation adjustments, the Company has elected to indefinitely reinvest the earnings of Centuri’s Canadian subsidiaries in Canada, thus preventing deferred taxes on such earnings. As a result of this assertion, and no repatriation of earnings anticipated, the Company is not recognizing a tax effect or presenting a tax expense or benefit for currency translation adjustments in Other comprehensive income (loss).

Approximately $416,000 of realized losses (net of tax) related to the remaining balance of Southwest’s previously settled FSIRS, included in AOCI at December 31, 2021, will be reclassified into interest expense within the next 3 months (the remainder of the amortization period for the balance) as the related interest payments on long-term debt occur.

The following table represents a rollforward of AOCI, presented on the Company’s Consolidated Balance Sheets and its Consolidated Statements of Equity:


	Defined Benefit Plans						FSIRS						Foreign Currency Items
(Thousands of dollars)	Before-Tax		Tax (Expense) Benefit (4)		After-Tax		Before- Tax		Tax (Expense) Benefit (4)		After-Tax		Before- Tax		Tax (Expense) Benefit		After-Tax		AOCI
Beginning Balance AOCI December 31, 2020	$	(77,720)	$	18,653	$	(59,067)	$	(2,719)	$	651	$	(2,068)	$	132	$	—	$	132	$	(61,003)
Net actuarial gain/(loss)	59,176		(14,202)		44,974		—		—		—		—		—		—		44,974
Translation adjustments	—		—		—		—		—		—		20		—		20		20
Other comprehensive income before reclassifications	59,176		(14,202)		44,974		—		—		—		20		—		20		44,994
FSIRS amount reclassified from AOCI (1)	—		—		—		2,174		(522)		1,652		—		—		—		1,652
Amortization of prior service cost (2)	959		(230)		729		—		—		—		—		—		—		729
Amortization of net actuarial loss (2)	44,597		(10,703)		33,894		—		—		—		—		—		—		33,894

Regulatory adjustment (3)	(88,194)		21,167		(67,027)		—		—		—				—		—		(67,027)
Net current period other comprehensive income (loss) attributable to Southwest Gas Holdings, Inc.	16,538		(3,968)		12,570		2,174		(522)		1,652		20		—		20		14,242
Ending Balance AOCI December 31, 2021	$	(61,182)	$	14,685	$	(46,497)	$	(545)	$	129	$	(416)	$	152	$	—	$	152	$	(46,761)

(1)The FSIRS reclassification amount is included in Net interest deductions on the Company’s Consolidated Statements of Income.

(2)These AOCI components are included in the computation of net periodic benefit cost (see Note 11 - Pension and Other Postretirement Benefits for additional details).

(3)The regulatory adjustment represents the portion of the activity above that is expected to be recovered through rates in the future (the related regulatory asset is included in Deferred charges and other assets on the Company’s Consolidated Balance Sheets).

(4) Tax amounts are calculated using a 24% rate.

The following table represents a rollforward of AOCI, presented on Southwest’s Consolidated Balance Sheets:


	Defined Benefit Plans						FSIRS
(Thousands of dollars)	Before-Tax		Tax (Expense) Benefit (9)		After- Tax		Before- Tax		Tax (Expense) Benefit (9)		After- Tax		AOCI
Beginning Balance AOCI December 31, 2020	$	(77,720)	$	18,653	$	(59,067)	$	(2,719)	$	651	$	(2,068)	$	(61,135)
Net actuarial gain/(loss)	59,176		(14,202)		44,974		—		—		—		44,974
Other comprehensive loss before reclassifications	59,176		(14,202)		44,974		—		—		—		44,974
FSIRS amount reclassified from AOCI (6)	—		—		—		2,174		(522)		1,652		1,652
Amortization of prior service cost (7)	959		(230)		729		—		—		—		729
Amortization of net actuarial loss (7)	44,597		(10,703)		33,894		—		—		—		33,894

Regulatory adjustment (8)	(88,194)		21,167		(67,027)		—		—		—		(67,027)
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation	16,538		(3,968)		12,570		2,174		(522)		1,652		14,222
Ending Balance AOCI December 31, 2021	$	(61,182)	$	14,685	$	(46,497)	$	(545)	$	129	$	(416)	$	(46,913)

(6) The FSIRS reclassification amount is included in Net interest deductions on Southwest’s Consolidated Statements of Income.

(7) These AOCI components are included in the computation of net periodic benefit cost (see Note 11 - Pension and Other Postretirement Benefits for additional details).

(8) The regulatory adjustment represents the portion of the activity above that is expected to be recovered through rates in the future (the related regulatory asset is included Deferred charges and other assets on Southwest’s Consolidated Balance Sheets).

(9) Tax amounts are calculated using a 24% rate.

The following table represents amounts (before income tax impacts) included in AOCI (in the tables above), that have not yet been recognized in net periodic benefit cost:


	Year Ended December 31,
(Thousands of dollars)	2021		2020
Net actuarial loss	$	(399,010)	$	(502,783)
Prior service cost	(1,528)		(2,487)
Less: amount recognized in regulatory assets	339,356		427,550
Recognized in AOCI	$	(61,182)	$	(77,720)

See Note 11 - Pension and Other Postretirement Benefits for more information on the defined benefit pension plans and Note 1 - Background, Organization, and Summary of Significant Accounting Policies for more information on the FSIRS.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496171-112644

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496171-112644

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (d)
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Common Stock

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Common Stock

Note 7 - Common Stock

Shares of the Company’s common stock are publicly traded on the New York Stock Exchange, under the ticker symbol “SWX.” Share-based compensation related to Southwest and Centuri is based on awards to be issued in shares of Southwest Gas Holdings, Inc.

On April 8, 2021, the Company entered into a Sales Agency Agreement between the Company and BNY Mellon Capital Markets, LLC and J.P. Morgan Securities LLC (the “Equity Shelf Program”) for the offer and sale of up to $500 million of common stock from time to time in an at-the-market offering program. The shares are issued pursuant to the Company’s automatic shelf registration statement on Form S-3 (File No. 333-251074). There was no activity in the program during the quarter ended December 31, 2021. The following table provides the life-to-date activity under the Equity Shelf Program for the period ended December 31, 2021:


Gross proceeds	$	158,180,343
Less: agent commissions	(1,581,803)
Net proceeds	$	156,598,540
Number of shares sold	2,302,407
Weighted average price per share	$	68.70

As of December 31, 2021, the Company had up to $341,819,657 of common stock available for future issuance under the program. Net proceeds from the sale of shares of common stock under the Equity Shelf Program are intended for general corporate purposes, including the acquisition of property for the construction, completion, extension, or improvement of pipeline systems and facilities located in and around the communities served by Southwest. Net proceeds during the twelve months ended December 31, 2021 were contributed to, and reflected in the records of, Southwest (as a capital contribution from Southwest Gas Holdings, Inc.).

Aside from the equity shelf registration, in December 2020, the Company and Southwest jointly filed with the SEC an automatic shelf registration statement (File No. 333-251074), or a “Universal Shelf,” which became effective upon filing and includes a prospectus detailing the Company’s ability to offer and sell, from time to time in amounts at prices and on terms that will be determined at the time of such offering, any combination of common stock, preferred stock, debt securities (which may or may not be guaranteed by one or more of its directly or indirectly wholly owned subsidiaries if indicated in the relevant prospectus supplement), guarantees of debt securities issued by Southwest, depository shares, warrants to purchase common stock, preferred stock or depository shares issued by the Company or debt securities issued by the Company or Southwest, units and rights. Additionally as part of the Universal Shelf, Southwest may offer and sell, from time to time in amounts at prices and on terms that will be determined at the time of such offering, any combination of debt securities (which may or may not be guaranteed by one or more of its directly or indirectly wholly owned subsidiaries if indicated in the relevant prospectus supplement) and guarantees of debt securities issued by the Company or by one or more of its directly or indirectly wholly owned subsidiaries if indicated in the relevant prospectus supplement.

During the quarter ended March 31, 2021, the Company sold essentially all of the remaining common stock available for sale under a previously effective equity shelf program.

During 2021, the Company issued approximately 48,000 shares of common stock through the Restricted Stock/Unit Plan and Omnibus Incentive Plan.

Additionally during 2021, the Company issued 173,000 shares of common stock through the Dividend Reinvestment and Stock Purchase Plan, raising proceeds of approximately $11.8 million.

As of December 31, 2021, there were 4.3 million shares of common stock registered and available for issuance under the provisions of the various stock issuance plans, which does not include the amount of common stock available that is separately disclosed with respect to the Equity Shelf Program above.

On October 10, 2021, the Company’s Board authorized and declared a dividend of one preferred stock purchase right (a “Right”) for each share of common stock outstanding, $1 par value per share, of the Company to stockholders of record at the close of business on October 21, 2021. Each right entitles the registered holder to purchase from the Company one ten-thousandth (a “unit”) of a share of Series A Junior Participating Preferred Stock, no par value per share, of the Company at a purchase price of $321.70 per unit, subject to adjustment. Generally, the Rights become exercisable in the event any person or group of affiliated or associated persons acquires beneficial ownership of 10% (20% in the case of a passive institutional investor) or more of the Company’s common stock without the approval of the Board, and until such time, are inseparable from and trade with the Company’s common stock. The Rights have a de minimis fair value. The Rights were issued pursuant to the Rights Agreement dated October 10, 2021 (the “Rights Agreement”), between the Company and Equiniti Trust Company, as rights agent. The Rights expire at the close of business on October 9, 2022 or upon an earlier merger or other acquisition transaction involving the Company, redemption, or exchange as provided in the Rights Agreement.

Debt

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Debt

Note 8 - Debt

Long-Term Debt

Long-term debt is recognized in the Company’s and Southwest’s Consolidated Balance Sheets generally at the carrying value of the obligations outstanding. However, details surrounding the fair value and individual carrying values of instruments are discussed below and provided in the table that follows.

Carrying amounts of long-term debt and related estimated fair values as of December 31, 2021 and 2020 are disclosed in the following table. The fair value hierarchy is described in Note 1 - Background, Organization, and Summary of Significant Accounting Policies.


	December 31,
	2021				2020
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
(Thousands of dollars)
Southwest Gas Corporation:
Debentures:
Notes, 6.1%, due 2041	$	125,000	$	166,380	$	125,000	$	174,858
Notes, 3.875%, due 2022	250,000		250,603		250,000		258,825
Notes, 4.875%, due 2043	250,000		307,538		250,000		317,190
Notes, 3.8%, due 2046	300,000		329,055		300,000		347,046
Notes, 3.7%, due 2028	300,000		325,191		300,000		344,553
Notes, 4.15%, due 2049	300,000		342,030		300,000		370,278
Notes, 2.2%, due 2030	450,000		440,838		450,000		474,552
Notes 3.18%, due 2051	300,000		292,116		—		—
8% Series, due 2026	75,000		92,623		75,000		99,723
Medium-term notes, 7.78% series, due 2022	25,000		25,122		25,000		26,663
Medium-term notes, 7.92% series, due 2027	25,000		31,555		25,000		33,802
Medium-term notes, 6.76% series, due 2027	7,500		8,949		7,500		9,613
Unamortized discount and debt issuance costs	(19,959)				(17,822)
	2,387,541				2,089,678
Revolving credit facility and commercial paper	130,000		130,000		150,000		150,000
Industrial development revenue bonds:
Tax-exempt Series A, due 2028	50,000		50,000		50,000		50,000
2003 Series A, due 2038	50,000		50,000		50,000		50,000
2008 Series A, due 2038	50,000		50,000		50,000		50,000
2009 Series A, due 2039	50,000		50,000		50,000		50,000
Unamortized discount and debt issuance costs	(1,938)				(1,472)
	198,062				198,528
Less: current maturities	(275,000)				—
Southwest Gas Corporation total long-term debt, less current maturities	$	2,440,603			$	2,438,206
Southwest Gas Holdings, Inc.:
Centuri secured term loan facility	$	1,117,138	$	1,117,841	$	226,648	$	230,824
Centuri secured revolving credit facility	103,329		103,749		26,626		26,645
MountainWest unsecured senior notes, 3.53%, due in 2028	102,078		102,078		—		—
MountainWest unsecured senior notes, 4.875%, due in 2041	199,926		199,926		—		—
MountainWest unsecured senior notes, 3.91%, due in 2038	147,735		147,735		—		—
Other debt obligations	51,665		50,003		81,973		84,246
Unamortized discount and debt issuance costs	(24,466)				(820)
Less: current maturities	(22,324)				(40,433)
Southwest Gas Holdings, Inc. total long-term debt, less current maturities	$	4,115,684			$	2,732,200

The fair values of Southwest's and the Company’s revolving credit facilities and Southwest’s Industrial Development Revenue Bonds (“IDRBs”) are categorized as Level 1 based on the FASB’s fair value hierarchy, due to the ability to access similar debt arrangements at measurement dates with comparable terms, including variable/market rates. Additionally, Southwest’s revolving credit facility and IDRBs have interest rates that reset frequently. The fair values of Southwest’s debentures (which include senior and medium-term notes) and the Company's term loan facility and unsecured senior notes as of December 31, 2021 were determined utilizing a market-based valuation approach, where fair values are determined based on evaluated pricing data, and as such are categorized as Level 2 in the hierarchy. Prior to amending its secured revolving credit and term loan facility in the third quarter 2021 (see below), the Company’s credit facility as it relates to Centuri was categorized as Level 3, as fair values were based on a conventional discounted cash flow methodology utilizing current market pricing yield curves.

Southwest has a $400 million credit facility that is scheduled to expire in April 2025. Southwest designates $150 million of associated capacity as long-term debt and the remaining $250 million for working capital purposes. Interest rates for the credit facility are calculated at either the Secured Overnight Financing Rate (“SOFR”) or an “alternate base rate” (as updated per its amended agreement below), plus in each case an applicable margin that is determined based on Southwest’s senior unsecured debt rating. At December 31, 2021, $130 million was outstanding on the long-term portion (no borrowings were outstanding under the commercial paper program discussed below). The effective interest rate on the long-term portion of the credit facility was 1.24% at December 31, 2021. Borrowings under the credit facility ranged from none at various times throughout 2021 to a high of $275 million during the first quarter of 2021.

On December 28, 2021, Southwest amended its credit facility agreement; total borrowing capacity under the amended agreement remained at $400 million. The amended agreement replaced the LIBOR interest rate benchmark with the SOFR interest rate benchmark. Under the amended agreement, the applicable margin ranges from 0.750% to 1.500% for loans bearing interest with reference to SOFR and from 0.000% to 0.500% for loans bearing interest with reference to an alternative base rate. At December 31, 2021, the applicable margin is 1.125% for loans with reference to SOFR and 0.125% for loans bearing interest with reference to the alternative base rate. Southwest is also required to pay a commitment fee on the unfunded portion of the commitments based on its senior unsecured long-term debt rating. The commitment fee on the unfunded portion of the commitments ranges from 0.075% to 0.200% per annum, and was not significant for the year ended December 31, 2021. The amended agreement contains certain representations and warranties and affirmative and negative covenants similar to those contained in the previous agreement. In addition, the amended agreement contains a financial covenant requiring Southwest to maintain a ratio of funded debt to total capitalization not to exceed 0.70 to 1.00 as of the end of any quarter of any fiscal year.

Southwest has a $50 million commercial paper program. Issuances under the commercial paper program are supported by Southwest’s current revolving credit facility and, therefore, do not represent additional borrowing capacity. Borrowings under the commercial paper program are designated as long-term debt. Interest rates for the program are calculated at the then current commercial paper rate. At December 31, 2021, as noted above, no borrowings were outstanding under the commercial paper program.

In August 2021, Southwest issued $300 million aggregate principal amount of 3.18% Senior Notes at a discount of 0.019%. The notes will mature in August 2051. Southwest used the net proceeds from the offering to repay the outstanding balance under its credit facility, with the remaining net proceeds used for general corporate purposes.

On August 27, 2021, Centuri, in association with the acquisition of Riggs Distler (see Note 15 - Business Acquisitions), entered into an amended and restated credit agreement. The agreement provided for a $1.145 billion secured term loan facility, at a discount of 1.00%, and a $400 million secured revolving credit facility; the combined facility, in addition to funding the Riggs Distler acquisition, refinanced the previous $590 million loan facility. This multi-currency facility allows the borrower to request loan advances in either Canadian dollars or U.S. dollars. Amounts borrowed and repaid under the revolving line of credit portion of the facility are available to be re-borrowed. The obligations under the credit agreement are secured by present and future ownership interests in substantially all direct and indirect subsidiaries of Centuri, substantially all of the tangible and intangible personal property of each borrower, certain of their direct and indirect subsidiaries, and all products, profits, and proceeds of the foregoing. The term loan facility matures on August 27, 2028 and the revolving credit facility matures on August 27, 2026.

Interest rates for the term loan facility and the revolving credit facility are based on either a “base rate” or LIBOR, plus an applicable margin in either case. The term loan facility is also subject to a LIBOR floor of 0.50%. Furthermore, Centuri Canada Division Inc. may borrow under the revolving credit facility with interest rates based on either a “base rate” or the Canadian Dealer Offered Rate (“CDOR”) plus the applicable margin, at the borrower’s option. The margin for the term loan facility will be 1.50% for base rate loans and 2.50% for LIBOR loans. The margin for the revolving credit facility ranges from 0.0% to 1.25% for base rate loans and from 1.00% to 2.25% for LIBOR loans, depending on Centuri’s net leverage ratio. Upon the occurrence of certain events providing for a transition away from LIBOR, or if LIBOR is no longer a widely recognized benchmark rate, Centuri may further amend the credit agreement with a replacement rate as set forth in the amended agreement. Centuri is also required to pay a commitment fee on the unused portion of the commitments. The commitment fee ranges from

0.150% to 0.35% per annum. The credit agreement contains certain customary representations and warranties, affirmative and negative covenants, and events of default. There are no financial covenants related to the term loan facility. The revolving credit facility requires Centuri to maintain a maximum total net leverage ratio of 5.50 to 1.00 with a step-down to 4.75 to 1.0 on December 31, 2022, and a step-down to 4.00 to 1.00 on December 31, 2023; provided, however, Centuri may elect to increase the maximum total net leverage ratio up to 4.50 to 1.00 in connection with certain material acquisitions, with such increase being applicable for one year following such acquisition; and the agreement also requires Centuri to maintain a minimum interest coverage ratio of 2.50 to 1.00. Centuri’s assets securing the facility at December 31, 2021 totaled $2.5 billion. Borrowings under the secured revolving credit portion of the facility ranged from a low of $103 million to a high of $116 million both during the fourth quarter of 2021. At December 31, 2021, $1.220 billion in borrowings were outstanding under Centuri’s combined secured revolving credit and term loan facility after having, among other things, funded the acquisition of Riggs.

All amounts outstanding are considered long-term borrowings. The effective interest rate on the secured revolving credit and term loan facility was 3.0% at December 31, 2021.

On December 31, 2021, the Company assumed a total of $449.7 million (the fair value on the acquisition date of $430 million in aggregate principal related to the debt) consisting of two private placement unsecured senior notes and public unsecured senior notes upon completion of the Questar Pipelines acquisition. Interest rates on the notes range from 3.53% to 4.875%, as depicted in the table above. The Company recorded the assumed debt at fair value as part of the purchase price allocation. See Note 15 - Business Acquisitions for additional information.

The effective interest rates on Southwest’s variable-rate IDRBs are included in the table below:


	December 31,
	2021		2020
2003 Series A	0.91	%	0.80	%
2008 Series A	0.90	%	0.83	%
2009 Series A	0.88	%	0.76	%
Tax-exempt Series A	0.92	%	0.87	%

In Nevada, interest fluctuations due to changing interest rates on Southwest’s 2003 Series A, 2008 Series A, and 2009 Series A variable-rate IDRBs are tracked and recovered from customers through a variable interest expense recovery mechanism.

None of Southwest’s debt instruments have credit triggers or other clauses that result in default if bond ratings are lowered by rating agencies. Interest and fees on certain debt instruments are subject to adjustment depending on Southwest’s bond ratings. Certain debt instruments are subject to a leverage ratio cap and the 6.1% Notes due 2041 are also subject to a minimum net worth requirement. At December 31, 2021, Southwest was in compliance with all of its covenants. Under the most restrictive of the financial covenants, approximately $2.9 billion in additional debt could be issued while still meeting the leverage ratio requirement. Relating to the minimum net worth requirement, as of December 31, 2021, there is at least $2 billion of cushion in equity. No specific dividend restrictions exist under the collective covenants. None of the debt instruments contain material adverse change clauses.

Certain Centuri debt instruments have leverage ratio caps and fixed charge ratio coverage requirements. At December 31, 2021, Centuri was in compliance with all of its covenants. Under the most restrictive of the covenants, Centuri could issue over $320 million in additional debt and meet the leverage ratio requirement. Centuri has at least $181 million of cushion relating to the minimum fixed charge ratio coverage requirement. Centuri’s covenants limit its ability to provide cash dividends to Southwest Gas Holdings, Inc., its parent. The dividend restriction is equal to a calculated available amount generally defined as 50% of its rolling twelve-month consolidated net income adjusted for certain items, such as parent contribution inflows, Linetec redeemable noncontrolling interest payments, or dividend payments, among other adjustments, as applicable.

Estimated maturities of long-term debt for the next five years are:


(Thousands of dollars)	2022		2023		2024		2025		2026		Total
Southwest Gas Corporation:
Debentures	$	275,000	$	—	$	—	$	—	$	75,000	$	350,000
Revolving credit facility and commercial paper	—		—		—		130,000		—		130,000
Total	275,000		—		—		130,000		75,000		480,000
Southwest Gas Holdings, Inc.:
Centuri secured term loan facility	11,450		11,450		11,450		11,450		11,450		57,250
Centuri secured revolving credit facility	—		—		—		—		103,329		103,329
Other debt obligations	10,874		11,047		11,285		9,076		7,490		49,772
Total	$	297,324	$	22,497	$	22,735	$	150,526	$	197,269	$	690,351

Short-Term Debt

Southwest Gas Holdings, Inc. has a $200 million credit facility that is primarily used for short-term financing needs. Interest rates for this facility are calculated at either SOFR or the “alternate base rate” (as updated per its amended agreement below), plus in each case an applicable margin that is determined based on the Company’s senior unsecured debt rating. Borrowings under the credit facility ranged from a low of $22 million during the fourth quarter of 2021 to a high of $59 million during the fourth quarter of 2021. There was $59 million and $50 million outstanding under this facility with a weighted average interest rate of 1.323% and 1.225% at December 31, 2021 and 2020, respectively.

On December 28, 2021, Southwest Gas Holdings, Inc. amended its existing credit facility. The amendment extended the maturity date of the credit facility to December 28, 2026, increased the total commitment amount from $100 million to $200 million, increased the amount which the total commitment may be increased (from $200 million to $300 million), and replaced the LIBOR interest rate benchmark with the SOFR interest rate benchmark. Interest rate benchmarks (SOFR or an alternative) as well as related ranges, including with regard to the applicable margin, largely mirror those included in Southwest’s amended facility agreement noted above, determined in this case based on Southwest Gas Holdings, Inc.’s senior unsecured long-term debt rating. At December 31, 2021, the applicable margin is 1.250% for loans bearing interest with reference to SOFR and 0.250% for loans bearing interest with reference to the alternative base rate. The commitment fee rates, terms and covenants, noted above for Southwest are also applicable to Southwest Gas Holdings, Inc. in its amended credit facility, including the noted ratio of funded debt to total capitalization as of the end of any quarter of any fiscal year. The commitment fee under this credit facility was not significant for the year ended December 31, 2021.

In March 2021, Southwest entered into a $250 million Term Loan that matures March 22, 2022. The proceeds were used to fund the increased cost of natural gas supply during the month of February 2021, caused by extreme weather conditions in the central U.S. (see Deferred Purchased Gas Costs in Note 1 - Background, Organization, and Summary of Significant Accounting Policies). Interest rates for the term loan are calculated at either LIBOR or an “alternate base rate,” plus in each case an applicable margin that is determined based on Southwest’s senior unsecured long-term debt rating. The applicable margin ranges from 0.550% to 1.000% for loans bearing interest with reference to LIBOR and 0.000% for loans bearing interest with reference to an alternate base rate. The agreement contains a financial covenant requiring Southwest to maintain a ratio of funded debt to total capitalization not to exceed 0.70 to 1.00 as of the end of any quarter of any fiscal year. The weighted average interest rate at December 31, 2021 was 0.800%.

In November 2021, the Company entered into a term loan credit agreement (the “Credit Agreement”). The Credit Agreement provided for a $1.6 billion delayed-draw term loan (the “Term Loan Facility”) to fund and pay fees, commissions, and expenses related to the Term Loan Facility and the acquisition by the Company of the equity interests in Questar Pipelines (refer to Note 15 - Business Acquisitions). The Term Loan Facility was funded on December 31, 2021, and matures on December 30, 2022. The interest rate for the Term Loan Facility is based on either “base rate” or LIBOR, plus an applicable margin in either case. The applicable margin for the Term Loan Facility is 0% to 0.50% for base rate loans and 0.75% to 1.50% for LIBOR loans, depending on the applicable pricing level in effect. Each of the interest rate spreads will increase by 0.25% at certain time intervals after the funding date. The commitment fee ranges from 0.060% to 0.175% per calendar quarter commencing January 3, 2022, depending on the applicable pricing level in effect. The pricing levels are based on the Company’s senior debt ratings. The interest rate is subject to customary benchmark replacement provisions. The weighted average interest rate at December 31, 2021 was 1.354%.

The Credit Agreement contains representations and warranties, affirmative, negative, and financial covenants and events of default substantially similar to the Company’s existing credit facility. Subject to certain exceptions, after the funding date, the

Company must make a mandatory prepayment from 100% of the net cash proceeds received by the Company or any of its subsidiaries from any debt offerings or equity issuances and/or 100% of the committed amount under any specified acquisition financings.

At December 31, 2021, Southwest Holdings, Inc. was in compliance with all of its credit facility and 364-day Term Loan covenants. Interest and fees on the credit facility and 364-day Term Loan are subject to adjustment depending on its senior debt ratings. The credit facility and 364-day Term Loan are subject to a leverage ratio cap. Under the most restrictive of the financial covenants, approximately $1 billion in additional debt could be issued while still meeting the leverage ratio requirement. No specific dividend restrictions exist under the collective covenants. The credit facility and 364-day Term Loan do not contain material adverse change clauses.

As indicated above, under Southwest’s $400 million credit facility, $250 million has been designated by management for working capital purposes. Southwest had no short-term borrowings outstanding at December 31, 2021 and $57 million of short-term borrowings outstanding with weighted average interest rate of 1.10%, at December 31, 2020.

The Company’s borrowing of $1.6 billion under the 364-day Term Loan, noted above, to temporarily finance the acquisition of Questar Pipelines created a negative working capital condition of approximately $1.5 billion. At December 31, 2021, total short-term debt was $1.909 billion and current maturities of long-term debt were $297 million. As of March 1, 2022, the Company does not have sufficient liquidity or capital resources to repay this debt at maturity without issuing new debt or equity. Management intends to satisfy these obligations through (i) the issuance of $900 million to $1 billion of equity and equity-linked instruments, (ii) the issuance of approximately $600 million to $700 million of long-term debt to permanently refinance the remaining portion of the 364-day Term Loan, and (iii) the issuance of approximately $600 million of bonds to refinance other current maturities of long-term debt obligations, and for other purposes.

Management believes that its refinancing plan is probable based on the Company’s ability to generate consistent cash flows, its current credit ratings, its relationships with its lenders and its prior history of successfully raising debt and equity necessary to fund its acquisitions and operations. As such, management has concluded that the Company can satisfy its obligations for at least the next twelve months from the issuance date of these financial statements.

The Company’s ability to access the capital markets or to otherwise obtain sufficient financing may be affected by future conditions. If the Company is unable to execute its plan to issue equity or refinance debt obligations, the Company’s credit facility could be terminated and amounts due under its revolver and other borrowing arrangements could be declared immediately due and payable.

LIBOR

Certain rates established at LIBOR are scheduled to be discontinued as a benchmark or reference rate after 2021, while other LIBOR-based rates are scheduled to be discontinued after June 2023. As of December 31, 2021, Southwest had $250 million in outstanding borrowings under its Term Loan and $130 million outstanding under its credit facility. At the same time, the Company had $3.2 billion in aggregate outstanding borrowings under Centuri’s combined facility, the Company’s Term Loan Facility, Southwest’s Term Loan, and credit facilities that have interest rates with reference to LIBOR and maturity dates that extend beyond 2021. The Southwest and Southwest Gas Holdings credit facilities were amended on December 28, 2021 to replace LIBOR interest rate benchmarks with SOFR interest rate benchmarks; however, amounts outstanding at December 31, 2021 under these credit facilities were referenced to LIBOR and subsequently repaid shortly after year end. In order to mitigate the impact on financial condition and results of operations to the Company and Southwest, management will monitor developments and work with lenders to determine the appropriate replacement/alternative reference rate for variable rate debt. At this time the Company and Southwest can provide no assurances as to the impact a LIBOR discontinuance will have on their financial condition or results of operations. Any alternative rate may be less predictable or less attractive than LIBOR.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-URI http://asc.fasb.org/topic&trid=2208564

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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+ Details

Share-Based Compensation

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Share-Based Compensation

Note 9 - Share-Based Compensation

At December 31, 2021, the following share-based compensation plans existed at the Company: an omnibus incentive plan and a restricted stock/unit plan. All share grants in 2021, including time-lapse restricted stock units and performance shares, occurred under the omnibus incentive plan. The table below shows total share-based plan compensation expense which was recognized in the Consolidated Statements of Income:


	Year Ended December 31,
(Thousands of dollars)	2021		2020		2019
Share-based compensation plan expense, net of related tax benefits	$	5,747	$	4,816	$	5,154
Share-based compensation plan related tax benefits	1,815		1,521		1,627

Omnibus Incentive Plan

The omnibus incentive plan is used to promote the long-term growth and profitability of the Company, including its subsidiaries, by providing directors, employees, and certain other individuals with incentives to increase stockholder value and otherwise contribute to the success of the Company. In addition, the plan enables the Company to attract, retain, and reward the best available persons for positions of responsibility. The omnibus incentive plan provides for the grant of stock options, stock appreciation rights, restricted stock, restricted stock units, performance shares, and other equity-based and cash awards. Employees, directors, and consultants who provide services to the Company or any subsidiary may be eligible under this plan. For grants under the omnibus incentive plan, directors continue to immediately vest in the shares upon grant but are provided the option to defer receipt of equity compensation until they leave the Board of Directors.

Performance-based incentive opportunities under the omnibus plan were granted to all officers of Southwest in the form of performance shares and are based, depending on the officer, on consolidated earnings per share, utility net income, and utility return on equity, with an adjustment based on relative total shareholder return, in each case, measured over a three-year performance period. Like other restricted stock/unit programs, shares are restricted based on vesting, and in this case, further subject to future performance determinations against relevant benchmarks. Southwest recorded $3.4 million, $2.8 million, and $2.3 million of estimated compensation expense associated with these shares during 2021, 2020, and 2019, respectively.

Restricted Stock/Units

Restricted stock/units under the restricted stock/unit plan were previously granted to attract, motivate, retain, and reward key employees of the Company with an incentive to attain high levels of individual performance and improved financial performance. The legacy plan was also established to attract, motivate, and retain experienced and knowledgeable directors. As noted above, grants of restricted stock during 2021, were granted under the omnibus incentive plan. All remaining shares under the legacy restricted stock/unit plan (in regard to employees) were issued during 2021; remaining unissued legacy program shares relate solely to directors, and such shares were immediately vested at the time of grant, with distribution to occur when service on the Board ends. No new grants are made under the legacy plan, as all future stock-based incentive compensation, including with regard to restricted stock, is granted under programs of the omnibus incentive plan, which for directors, with advance election, issuance may occur upon grant. Conversely, with regard to management, grants under the omnibus plan are of time-lapse character, with graded vesting (and issuance in the form of common stock) occurring, 40% at the end of year one and 30% at the end of years two and three.

The following table summarizes the activity of the restricted stock/units programs as of December 31, 2021:


(Thousands of shares)	Restricted Stock/ Units (1)	Weighted- average grant date fair value
Nonvested/unissued at December 31, 2020	401	$	62.23
Granted	188	65.38
Dividends	10
Forfeited or expired	(9)	70.09
Vested and issued (2)	(70)	69.87
Nonvested/unissued at December 31, 2021	520	$	61.01

(1)The number of performance shares includes 120,400 granted and 31,400 vested and issued, which was derived by assuming that target performance will be achieved during the relevant performance period.

(2)Includes shares for retiree payouts and those converted for taxes.

The weighted average grant date fair value of all restricted stock/units granted in 2020 and 2019 was $62.23 and $81.75, respectively.

As of December 31, 2021, total compensation cost related to all nonvested omnibus shares not yet recognized is $5.2 million, which is expected to be recognized over a weighted average period of 1.7 years.

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 10 - Commitments and Contingencies The Company and Southwest are defendants in miscellaneous legal proceedings. They are also parties to various regulatory proceedings. The ultimate dispositions of these proceedings are not presently determinable; however, it is the opinion of management that no litigation or regulatory proceeding to which the Company and Southwest are currently subject will have a material adverse impact on their financial position, results of operations, or cash flows. The Company maintains liability insurance that covers both Southwest and Questar Pipelines for various risks associated with the operation of the natural gas pipelines and facilities. In connection with these liability insurance policies, each entity is responsible for an initial deductible or self-insured retention amount per incident, after which the insurance carriers would be responsible for amounts up to the policy limits. For the policy year August 2021 to July 2022, these liability insurance policies require Southwest or Questar Pipelines, as applicable, to be responsible for the first $1 million (self-insured retention) of each incident plus the first $4 million in aggregate claims above its self-insured retention in the policy year. Centuri maintains liability insurance for various risks associated with its operations. In connection with these liability insurance policies, Centuri is responsible for an initial deductible or self-insured retention amount per occurrence, after which the insurance carriers would be responsible for amounts up to the policy limits. For the policy year May 2021 to April 2022, Centuri is responsible for the first $750,000 (self-insured retention) per occurrence under these liability insurance policies. In August 2021, natural gas pipe operated by Southwest was involved in an explosion that injured four individuals and damaged property. The explosion was caused by a leak in the pipe, and is under investigation. One of the individuals and his family have formally filed a legal claim against Southwest and other parties. If Southwest is deemed fully or partially responsible, Southwest estimates its exposure could be as much as $5 million (the maximum noted above). For the year ended December 31, 2021, pursuant to Accounting Standards Codification 450, Contingencies, Southwest recorded a $5 million liability related to this incident reflecting the maximum noted above; an estimate of actual loss greater than this exposure (to be covered by insurance) cannot be estimated as of the date these financial statements are issued. On November 29, 2021, Icahn Partners LP and Icahn Master Fund LP (collectively, “Icahn”) commenced an action in the Court of Chancery for the State of Delaware. The action is captioned Icahn Partners LP, et al. v. John P. Hester, et al., C.A. No. 2021-1031-KSJM (Del. Ch.). The complaint names the Company and the individual members of the Board as defendants. The complaint seeks to allege breach of fiduciary duty claims and, among other things, seeks declaratory and injunctive relief to (1) limit the scope and manner of certain equity issuances by the Company; (2) allow Icahn to proceed with a Special Meeting proposal at the Company’s 2022 Annual Meeting; and (3) require the Board to approve Icahn’s slate of nominees as “continuing directors” under certain of the Company’s debt instruments. After filing the complaint, Icahn sought a temporary restraining order to prohibit defendants from making certain equity issuances. On December 21, 2021, the Court denied Icahn’s request. On January 19, 2022, the defendants filed a motion to dismiss the claims that were subject to Icahn’s motion for a temporary restraining order. The same day, the defendants filed an answer, denying the remaining claims in Icahn’s complaint. A hearing on the claim regarding a proposal for a Special Meeting is set for March 15, 2022. The Company believes that the claims lack merit and intends to vigorously defend against them. On November 18, 2021, the City Pension Fund for Firefighters and Police Officers in the City of Miami Beach commenced a putative class action lawsuit in the Court of Chancery for the State of Delaware on behalf of a putative class of persons who purchased the Company’s stock. The action is captioned City Pension Fund for Firefighters and Police Officers in the City of Miami Beach v. Robert L. Boughner, et al., C.A. No. 2021-0990-KSJM (Del. Ch.). The complaint was later amended on November 30, 2021. The amended complaint names the Company and the individual members of the Board as defendants. The complaint seeks to assert breach of fiduciary duty claims, alleging that the Board’s recommendation that stockholders reject Icahn’s tender offer to purchase shares of the Company’s common stock omitted material information about the Company’s financial analysis; and seeks to have the Board approve Icahn’s slate of nominees as “continuing directors” under certain of the Company’s debt instruments. The Company believes that the claims lack merit and intends to vigorously defend against them. Through an assessment process of commitments and contingencies of any kind, the Company and Southwest may determine that certain costs are likely to be incurred in the future related to specific legal matters. In these circumstances and in accordance with accounting policies, the Company and Southwest will make an accrual, as necessary.

Pension and Other Postretirement Benefits

12 Months Ended

Dec. 31, 2021

Retirement Benefits [Abstract]

Pension and Other Postretirement Benefits

Note 11 - Pension and Other Postretirement Benefits

Southwest Gas Corporation

Employees’ Investment Plan

An Employees’ Investment Plan (“EIP”) is offered to eligible employees of Southwest through deduction of a percentage of base compensation, subject to IRS limitations. The EIP provides for purchases of various mutual fund investments and Company common stock. One-half of amounts deferred by existing employees as of December 31, 2021 are matched, up to a maximum matching contribution of 3.5% of an employee’s annual compensation. Employees hired on or after January 1, 2022, will be eligible for enhanced defined contributions as part of the EIP rather than participating in the defined benefit qualified retirement plan. The change is not applicable to employees hired on or before December 31, 2021. Enhanced EIP benefits for employees hired after 2021 will include employer contributions of 3% plus a matching contribution (dollar-for-dollar) up to 7% of eligible compensation. There are no employer matching contributions for officer deferrals into the EIP. Contributions to the plan by Southwest were $6.1 million, $5.9 million, and $5.7 million for 2021, 2020, and 2019, respectively.

Deferred Compensation Plan

A deferred compensation plan is offered to all officers of Southwest and a separate deferred compensation plan is offered to members of the Company’s Board of Directors. The plans provide the opportunity to defer up to 100% of annual cash

compensation. One-half of amounts deferred by officers are matched, up to a maximum matching contribution of 3.5% of an officer’s annual base salary. Upon retirement, payments of compensation deferred, plus interest, are made in equal monthly installments over 10, 15, or 20 years, as elected by the participant. Directors have an additional option to receive such payments over a five-year period. Deferred compensation earns interest at a rate determined each January. The interest rate equals 150% of Moody’s Seasoned Corporate Bond Rate Index.

Pension and Postretirement Plans

A noncontributory qualified retirement plan with defined benefits covering substantially all Southwest employees hired on or before December 31, 2021 is available, in addition to a separate unfunded supplemental executive retirement plan (“SERP”), which is limited to Southwest’s officers. Postretirement benefits other than pensions (“PBOP”) are provided to qualified retirees for health care, dental, and life insurance benefits. The defined benefit qualified retirement plan, SERP, and PBOP are not available to Southwest employees hired on or after January 1, 2022. As noted above, employees hired on or after that date, are eligible for enhanced contributions to the EIP.

The overfunded or underfunded positions of defined benefit postretirement plans, including pension plans, are recognized in the Consolidated Balance Sheets. Any actuarial gains and losses, prior service costs, and transition assets or obligations are recognized in Accumulated other comprehensive income under Stockholders’ equity, net of tax, until they are amortized as a component of net periodic benefit cost.

A regulatory asset has been established for the portion of the total amounts otherwise chargeable to Accumulated other comprehensive income that are expected to be recovered through rates in future periods. Changes in actuarial gains and losses and prior service costs pertaining to the regulatory asset will be recognized as an adjustment to the regulatory asset account as these amounts are amortized and recognized as components of net periodic pension costs each year.

The qualified retirement plan invests the majority of its plan assets in common collective trusts, which include a well-diversified portfolio of domestic and international equity securities and fixed income securities, and are managed by a professional investment manager appointed by Southwest. The investment manager has full discretionary authority to direct the investment of plan assets held in trust within the specific guidelines prescribed by Southwest through the plan’s investment policy statement. In 2016, Southwest adopted a liability driven investment (“LDI”) strategy for part of the portfolio, a form of investing designed to better match the movement in pension plan assets with the impact of interest rate changes and inflation assumption changes on the pension plan liability. The implementation of the LDI strategy will be phased in over time by using a glide path. The glide path is designed to increase the allocation of the plan’s assets to fixed income securities, as the funded status of the plan increases, in order to more closely match the duration of the plan assets to that of the plan liability. Pension plan assets are held in a Master Trust. The pension plan funding policy is in compliance with the federal government’s funding requirements.

Pension costs for these plans are affected by the amount and timing of cash contributions to the plans, the return on plan assets, discount rates, and by employee demographics, including age, compensation, and length of service. Changes made to the provisions of the plans may also impact current and future pension costs. Actuarial formulas are used in the determination of pension costs and are affected by actual plan experience and assumptions about future experience. Key actuarial assumptions include the expected return on plan assets, the discount rate used in determining the projected benefit obligation and pension costs, and the assumed rate of increase in employee compensation. Relatively small changes in these assumptions, particularly the discount rate, may significantly affect pension costs and plan obligations for the qualified retirement plan. In determining the discount rate, management matches the plan’s projected cash flows to a spot-rate yield curve based on highly rated corporate bonds. Changes to the discount rate from year-to-year, if any, are generally made in increments of 25 basis points.

While there continues to persist an historically low interest rate environment, there was a 25 basis point increase in the discount rate between years, as reflected below. The discount rate was a significant contributor to the actuarial losses for the qualified retirement plan, SERP, and PBOP plans in the previous year, when the discount rate, instead, dropped 75 basis points. The methodology utilized to determine the discount rate was consistent with prior years. The weighted-average rate of compensation increased from the prior year by 25 basis points. The asset return assumption (which impacts the following year’s expense) remained consistent with the prior year. The rates are presented in the table below:


	December 31,
	2021		2020
Discount rate	3.00	%	2.75	%
Weighted-average rate of compensation increase	3.25	%	3.00	%
Asset return assumption	6.50	%	6.50	%

Future years’ expense level movements (up or down) will continue to be greatly influenced by long-term interest rates, asset returns, and funding levels.

The following table sets forth the retirement plan, SERP, and PBOP funded statuses and amounts recognized on the Consolidated Balance Sheets and Consolidated Statements of Income.


	Year Ended December 31,
	2021									2020
(Thousands of dollars)	Qualified Retirement Plan			SERP			PBOP			Qualified Retirement Plan			SERP			PBOP
Change in benefit obligations:
Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO)	$	1,499,239		$	53,631		$	82,205		$	1,329,577		$	47,397		$	76,111
Service cost	41,159			526			1,691			34,299			389			1,581
Interest cost	40,432			1,431			2,193			45,555			1,604			2,582

Actuarial loss (gain)	8,908			(3,244)			3,438			145,440			7,240			6,547
Benefits paid	(58,541)			(2,814)			(5,301)			(55,632)			(2,999)			(4,616)
Benefit obligation at end of year (PBO/PBO/APBO)	1,531,197			49,530			84,226			1,499,239			53,631			82,205
Change in plan assets:
Market value of plan assets at beginning of year	1,186,433			—			52,286			974,993			—			52,838
Actual return on plan assets	136,151			—			7,717			165,072			—			5,320
Employer contributions	102,000			2,814			—			102,000			2,999			—
Benefits paid	(58,541)			(2,814)			(7,835)			(55,632)			(2,999)			(5,872)
Market value of plan assets at end of year	1,366,043			—			52,168			1,186,433			—			52,286
Funded status at year end	$	(165,154)		$	(49,530)		$	(32,058)		$	(312,806)		$	(53,631)		$	(29,919)
Weighted-average assumptions (benefit obligation):
Discount rate	3.00		%	3.00		%	3.00		%	2.75		%	2.75		%	2.75		%
Weighted-average rate of compensation increase	3.25		%	3.25		%	N/A			3.00		%	3.00		%	N/A

Estimated funding for the plans above during calendar year 2022 is approximately $59 million, of which $56 million pertains to the retirement plan. Management monitors plan assets and liabilities and may, at its discretion, increase plan funding levels above the minimum in order to achieve a desired funded status and avoid or minimize potential benefit restrictions. As a result of the impact of the historically low discount rates at December 31, 2020, Southwest made a discretionary supplemental contribution of $50 million in January 2021, which was intended to mitigate the impacts on the funded status and the increase in pension costs in the prior year, through the ability to provide returns on the increased level of plan investments. As a result, total pension funding in 2021 was $102 million.

The accumulated benefit obligation for the retirement plan and the SERP is presented below:


	December 31,
(Thousands of dollars)	2021		2020
Retirement plan	$	1,395,773	$	1,367,179
SERP	46,885		50,471

Benefits expected to be paid for pension, SERP, and PBOP over the next 10 years are as follows:


(Millions of dollars)	2022		2023		2024		2025		2026		2027-2031
Pension	$	62.0	$	64.0	$	65.0	$	67.0	$	68.0	$	365.0
SERP	3.0		3.0		3.0		3.0		2.9		13.9
PBOP	5.0		5.2		5.2		5.2		5.3		27.3

No assurance can be made that actual funding and benefits paid will match these estimates.

For PBOP measurement purposes, the per capita cost of the covered health care benefits medical rate trend assumption is 6.0%, declining to 4.5%. Specific contributions are made for health care benefits of employees who retire after 1988, but Southwest pays all covered health care costs for employees who retired prior to 1989. The medical trend rate assumption noted above applies to the benefit obligations of pre-1989 retirees only.

The service cost component of net periodic benefit costs included in the table below is part of an overhead loading process associated with the cost of labor. The overhead process ultimately results in allocation of that portion of overall net periodic benefit costs to the same accounts to which productive labor is charged. As a result, service costs become components of various accounts, primarily Operations and maintenance expense, Net regulated operations plant, and Deferred charges and other assets for both the Company and Southwest. The non-service cost components of net periodic benefit cost are reflected in Other income (deductions) on the Consolidated Statements of Income of each entity, based on accounting guidance for the presentation of such costs.

Components of net periodic benefit cost:


	Qualified Retirement Plan						SERP						PBOP
(Thousands of dollars)	2021		2020		2019		2021		2020		2019		2021		2020		2019
Service cost	$41,159		$34,299		$25,864		$526		$389		$266		$1,691		$1,581		$1,276
Interest cost	40,432		45,555		49,006		1,431		1,604		1,760		2,193		2,582		3,046
Expected return on plan assets	(72,352)		(65,296)		(60,244)		—		—		—		(3,239)		(3,408)		(3,156)
Amortization of prior service cost	—		—		—		—		—		—		959		1,155		1,271
Amortization of net actuarial loss	41,955		36,025		22,356		2,642		1,805		1,020		—		—		—
Net periodic benefit cost	$51,194		$50,583		$36,982		$4,599		$3,798		$3,046		$1,604		$1,910		$2,437
Weighted-average assumptions (net benefit cost)
Discount rate	2.75	%	3.50	%	4.50	%	2.75	%	3.50	%	4.50	%	2.75	%	3.50	%	4.50	%
Expected return on plan assets	6.50	%	6.75	%	7.00	%	N/A		N/A		N/A		6.50	%	6.75	%	7.00	%
Weighted-average rate of compensation increase	3.00	%	3.25	%	3.25	%	3.00	%	3.25	%	3.25	%	N/A		N/A		N/A

Other Changes in Plan Assets and Benefit Obligations Recognized in Net Periodic Benefit Cost and Other Comprehensive Income


	Year Ended December 31,
	2021								2020								2019
(Thousands of dollars)	Total		Qualified Retirement Plan		SERP		PBOP		Total		Qualified Retirement Plan		SERP		PBOP		Total		Qualified Retirement Plan		SERP		PBOP
Net actuarial loss (gain) (a)	$	(59,176)	$	(54,892)	$	(3,245)	$	(1,039)	$	57,539	$	45,665	$	7,240	$	4,634	$	71,087	$	66,557	$	7,975	$	(3,445)
Amortization of prior service cost (b)	(959)		—		—		(959)		(1,155)		—		—		(1,155)		(1,271)		—		—		(1,271)
Amortization of net actuarial loss (b)	(44,597)		(41,955)		(2,642)		—		(37,830)		(36,025)		(1,805)		—		(23,376)		(22,356)		(1,020)		—
Prior service cost	—		—		—		—		—		—		—		—		1,878		—		—		1,878
Regulatory adjustment	88,194		86,196		—		1,998		(7,435)		(3,956)		—		(3,479)		(36,944)		(39,782)		—		2,838
Recognized in other comprehensive (income) loss	(16,538)		(10,651)		(5,887)		—		11,119		5,684		5,435		—		11,374		4,419		6,955		—
Net periodic benefit costs recognized in net income	57,397		51,194		4,599		1,604		56,291		50,583		3,798		1,910		42,465		36,982		3,046		2,437
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss	$	40,859	$	40,543	$	(1,288)	$	1,604	$	67,410	$	56,267	$	9,233	$	1,910	$	53,839	$	41,401	$	10,001	$	2,437

The table above discloses the net gain or loss and prior service cost recognized in Other comprehensive income, separated into (a) amounts initially recognized in Other comprehensive income, and (b) amounts subsequently recognized as adjustments to Other comprehensive income as those amounts are amortized as components of net periodic benefit cost. See also Note 6 - Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI").

The following table sets forth, by level within the three-level fair value hierarchy, the fair values of the assets of the qualified pension plan and the PBOP as of December 31, 2021 and 2020. The SERP has no assets.


	December 31,
	2021						2020
(Thousands of dollars)	Qualified Retirement Plan		PBOP		Total		Qualified Retirement Plan		PBOP		Total
Assets at fair value:
Level 1 – Quoted prices in active markets for identical financial assets
Mutual funds	$	—	$	35,194	$	35,194	$	—	$	30,358	$	30,358
Total Level 1 Assets (1)	—		35,194		35,194		—		30,358		30,358
Level 2 – Significant other observable inputs
Private commingled equity funds (2)
Global	373,936		4,538		378,474		324,084		5,878		329,962
International	158,461		1,923		160,384		141,290		2,563		143,853
U.S. equity securities	279,062		3,386		282,448		223,374		4,051		227,425
Emerging markets	82,004		995		82,999		76,679		1,391		78,070
Private commingled fixed income funds (3)	463,942		5,630		469,572		412,230		7,476		419,706
Pooled funds and mutual funds	5,979		500		6,479		5,990		565		6,555
Government fixed income and mortgage backed securities	196		2		198		201		4		205
Total Level 2 assets (4)	1,363,580		16,974		1,380,554		1,183,848		21,928		1,205,776
Total Plan assets at fair value	1,363,580		52,168		1,415,748		1,183,848		52,286		1,236,134
Insurance company general account contracts (5)	2,463		—		2,463		2,585		—		2,585
Total Plan assets	$	1,366,043	$	52,168	$	1,418,211	$	1,186,433	$	52,286	$	1,238,719

(1)The Mutual funds category above is a balanced fund that invests in a diversified portfolio of common stocks, preferred stocks, and fixed-income securities. Under normal circumstances the balanced fund will hold no more than 75%, and no less than 25%, of its total assets in equity securities. The fund seeks regular income, conservation of principal, and an opportunity for long-term growth of principal and income.

(2)The private commingled equity funds include common collective trusts that invest in a diversified portfolio of securities regularly traded on securities exchanges. These funds are shown in the above table at net asset value (“NAV”), which is the value of securities in the fund less the amount of any liabilities outstanding. Strategies employed by the funds include investment in:

▪Global equities, including domestic equities

▪International developed countries equities

▪Domestic equities

▪Emerging markets equities

Shares in the private commingled equity funds may be redeemed given one business day notice. While they are private equity funds and reported at NAV, due to the short redemption notice period, the lack of redemption fees, the fact that the underlying investments are exchange-traded, and that substantial liabilities do not exist subject to the NAV calculation, these investments are viewed as indirectly observable (Level 2) in the fair value hierarchy and are therefore not excluded from the body of the fair value table as a reconciling item.

The global fund provides diversified exposure to global equity markets. The fund seeks to provide long-term capital growth by investing primarily in securities listed on the major developed equity markets of the U.S., Europe, and Asia, as well as within those listed on emerging country equity markets on a tactical basis.

The international fund invests in international financial markets, primarily those of developed economies in Europe and the Pacific Basin. The fund invests primarily in equity securities issued by foreign corporations, but may invest in other securities perceived as offering attractive investment return opportunities.

The domestic equities securities funds include a large and medium capitalization fund and a small capitalization fund. The large and medium capitalization fund is designed to track the performance of the large and medium capitalization companies contained in the index, which represents approximately 90% of the market capitalization of the U.S. stock market. The small capitalization fund is designed to provide maximum long-term appreciation through investments that are well diversified by industry.

The emerging markets fund was developed to invest in emerging market equities worldwide. The purposes of the fund’s operations, “emerging market countries,” include every country in the world except the developed markets of the U.S., Canada, Japan, Australia, New Zealand, Hong Kong, and Singapore, and most countries located in Western Europe. Fund investments are made directly in each country or, where direct investment is inefficient or prohibited, through appropriate financial instruments or participation in commingled funds.

(3)The private commingled fixed income funds consist primarily of fixed income debt securities issued by the U.S. Treasury, government agencies, and fixed income debt securities issued by corporations. The fixed income fund investments may include the use of

high yield, international fixed income securities and other instruments, including derivatives, to ensure prudent diversification over a broad spectrum of investments. The changes in the value of the fixed income funds are intended to offset the changes in the pension plan liabilities due to changes in the discount rate.

These funds are shown in the above table at NAV. Investments in the private commingled fixed equity funds may be redeemed given one business day notice. While they are private fixed income funds and reported at NAV, due to the short redemption notice period, the lack of redemption fees, the fact that the underlying investments are exchange-traded, and that substantial liabilities do not exist subject to the NAV calculation, these investments are viewed as indirectly observable (Level 2), and are also not excluded from the body of the fair value table as a reconciling item.

(4)With the exception of items (2) and (3), which are discussed above, the Level 2 assets consist mainly of pooled funds and mutual funds. These funds are collective short-term funds that invest in Treasury bills and money market funds and are used as a temporary cash repository.

(5)The insurance company general account contracts are annuity insurance contracts used to pay the pensions of employees who retired prior to 1989. The balance of the account disclosed in the above table is the contract value, which is the result of deposits, withdrawals, and interest credits.

Centuri

Defined Contribution Plans

Centuri offers defined contribution plans under Section 401(k) of the Internal Revenue Code to its eligible employees, regardless of whether they are covered under collective-bargaining agreements. Eligibility requirements vary, as does timing of participation, matching, vesting, and profit-sharing features of the plans. Contributions by Centuri to these plans for the years ended December 31, 2021, 2020, and 2019 were $9 million, $9 million, and $8 million, respectively.

Deferred Compensation Plan

Centuri sponsors a nonqualified deferred compensation plan that is offered to a select group of management and highly-compensated employees. The plan allows participants to defer up to 80% of base salary and provides a match of 100% of contributions up to 5% of a participant’s salary. The plan also allows Centuri, at its election, to credit participant accounts with discretionary contributions. Participants are 100% vested in salary deferrals, contributions, and all earnings. Participant accounts include a return based on the performance of the underlying investment options selected. Payments from the plan are designated at each annual enrollment period based on specified triggering events and are payable by lump sum or on an annual installment basis.

Multiemployer Pension Plans

Centuri makes defined contributions to several multiemployer defined benefit pension plans under the terms of collective bargaining agreements (“CBAs”) with various unions representing certain employees. Contribution rates are generally specified in the CBAs and are made to the plans on a “pay-as-you-go” basis. Such contributions correspond to the number of union employees and the particular plans in which they participate, and vary depending upon the location, number of ongoing projects, and the need for union resources in connection with those projects.

The risks of participating in multiemployer plans are different from single-employer plans, including: (i) assets contributed to the multiemployer plan by one employer may be used to provide benefits to employees of other participating employers; (ii) if a participating employer stops contributing to the multiemployer plan, the unfunded obligations of the plan may become the obligation of the remaining participating employers; and (iii) if a participating employer chooses to stop participating in these multiemployer plans, the employer may be required to pay those plans an amount based on the underfunded status of the plan.

The Pension Protection Act of 2006 requires special funding and operational rules for multiemployer plans in the U.S., including classification of the plans (based on multiple factors, including the funded status of the plan), the most severe of which is “critical.” Depending upon the classification, plans may be required to adopt measures to improve their funded status through a funding improvement or rehabilitation plan, which may require additional contributions from employers (in the form of a surcharge on benefit contributions) and/or modification of retiree benefits. The amount of additional funds, if any, that Centuri may be obligated to contribute to these plans in the future cannot be estimated due to the uncertainty regarding future levels of work that may require the utilization of union employees covered by these plans, as well as uncertainty as to the future contribution levels and possible surcharges on contributions that may apply to these plans at that time.

Centuri contributed $57.4 million, $44.3 million, and $41.3 million collectively to the plans for the years ended December 31, 2021, 2020, and 2019, respectively. Substantially all of the contributions made by Centuri during these years were to U.S. plans that were not classified as critical, and for which no special surcharges were assessed. Only six plans were classified as critical and required special surcharges; however, the contributions overall related to these plans in all periods were insignificant.

- Definition

The entire disclosure for retirement benefits.

+ References

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-Name Accounting Standards Codification
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+ Details

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

Note 12 - Income Taxes

Southwest Gas Holdings, Inc.:

The following is a summary of income before taxes and noncontrolling interests for domestic and foreign operations:


	Year ended December 31,
(Thousands of dollars)	2021		2020		2019
U.S.	$	221,507	$	282,489	$	261,525
Foreign	25,343		22,249		11,145
Total income before income taxes	$	246,850	$	304,738	$	272,670

Income tax expense (benefit) consists of the following:


	Year Ended December 31,
(Thousands of dollars)	2021		2020		2019
Current:
Federal	$	(2,872)	$	6,287	$	622
State	(11,516)		8,617		(1,510)
Foreign	6,524		4,666		5,013
	(7,864)		19,570		4,125
Deferred:
Federal	39,117		44,547		45,593
State	8,239		414		8,212
Foreign	156		1,222		(1,907)
	47,512		46,183		51,898
Total income tax expense	$	39,648	$	65,753	$	56,023

Deferred income tax expense (benefit) consists of the following significant components:


	Year Ended December 31,
(Thousands of dollars)	2021		2020		2019
Deferred federal and state:
Property-related items	$	35,072	$	50,504	$	60,449
Purchased gas cost adjustments	73,613		(5,726)		3,834
Employee benefits	(1,484)		459		7,680
Regulatory adjustments	(10,101)		(9,885)		(11,962)
Deferred payroll taxes	(6,344)		(9,055)		—
Deferred revenue	6,021		588		822
Net operating loss	(65,509)		3,349		5,658
Alternative minimum tax	—		4,409		441
All other deferred	16,296		11,592		(14,778)
Total deferred federal and state	47,564		46,235		52,144
Deferred ITC, net	(52)		(52)		(246)
Total deferred income tax expense	$	47,512	$	46,183	$	51,898

References above and below to Deferred payroll taxes relate to the employer portion of Social Security tax, for which deferment of remittance was permissible under the Coronavirus Aid, Relief, and Economic Security (“CARES”) Act.

A reconciliation of the U.S. federal statutory rate to the consolidated effective tax rate (and the sources of these differences and the effect of each) are summarized as follows:


	Year Ended December 31,
	2021		2020		2019
U.S. federal statutory income tax rate	21.0	%	21.0	%	21.0	%
Net state taxes	1.0		3.0		2.1
Tax credits	(0.5)		(0.5)		(0.3)
Company-owned life insurance	(1.1)		(0.8)		(1.5)

Amortization of excess deferred taxes	(4.3)		(0.8)		(0.9)
All other differences	—		(0.3)		0.1
Consolidated effective income tax rate	16.1	%	21.6	%	20.5	%

Deferred tax assets and liabilities consist of the following:


	December 31,
(Thousands of dollars)	2021		2020
Deferred tax assets:
Deferred income taxes for future amortization of ITC and excess deferred taxes	$	116,496	$	104,314
Employee benefits	39,181		39,907

Federal net operating losses	94,383		4,118
Deferred payroll taxes	6,344		9,055
Lease-related item	18,462		20,890
Other	15,739		14,350
Valuation allowance	(22)		(22)
	290,583		192,612
Deferred tax liabilities:
Property-related items, including accelerated depreciation	843,559		785,734
Regulatory balancing accounts	77,818		4,205

Debt-related costs	2,277		2,585
Intangibles	97,860		13,511
Lease-related item	17,254		19,789
Other	20,562		13,786
	1,059,330		839,610
Net noncurrent deferred tax liabilities	$	768,747	$	646,998

Net noncurrent deferred tax liabilities above at December 31, 2021 and 2020 are reflected net of $121,000 and $455,000 of noncurrent deferred tax assets associated with the Company’s Canadian operations, which are shown separately on the Company’s Consolidated Balance Sheets.

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:


	December 31,
(Thousands of dollars)	2021		2020
Unrecognized tax benefits at beginning of year	$	1,928	$	1,056
Gross increases – tax positions in prior period	442		641
Gross decreases – tax positions in prior period	—		—
Gross increases – current period tax positions	259		231
Gross decreases – current period tax positions	—		—
Settlements	—		—
Lapse in statute of limitations	—		—
Unrecognized tax benefits at end of year	$	2,629	$	1,928

Southwest Gas Corporation:

The following is a summary of income before taxes:


	Year ended December 31,
(Thousands of dollars)	2021		2020		2019
Total income before income taxes	$	216,473	$	194,873	$	198,144

Income tax expense (benefit) consists of the following:


	Year Ended December 31,
(Thousands of dollars)	2021		2020		2019
Current:
Federal	$	(3,643)	$	(4,678)	$	4,109
State	(6,556)		(179)		250
	(10,199)		(4,857)		4,359
Deferred:
Federal	36,842		38,561		29,543
State	2,695		2,051		1,071
	39,537		40,612		30,614
Total income tax expense	$	29,338	$	35,755	$	34,973

Deferred income tax expense (benefit) consists of the following significant components:


	Year Ended December 31,
(Thousands of dollars)	2021		2020		2019
Deferred federal and state:
Property-related items	$	23,077	$	36,029	$	34,398
Purchased gas cost adjustments	73,613		(5,726)		3,834
Employee benefits	5,508		11,437		6,493
Regulatory adjustments	(10,101)		(9,885)		(11,962)
Deferred payroll taxes	(892)		(1,810)		—
Alternative minimum tax	—		4,409		441
Net operating loss	(59,119)		—		—
All other deferred	7,503		6,210		(2,344)
Total deferred federal and state	39,589		40,664		30,860
Deferred ITC, net	(52)		(52)		(246)
Total deferred income tax expense	$	39,537	$	40,612	$	30,614

A reconciliation of the U.S. federal statutory rate to the consolidated effective tax rate (and the sources of these differences and the effect of each) are summarized as follows:


	Year Ended December 31,
	2021		2020		2019
U.S. federal statutory income tax rate	21.0	%	21.0	%	21.0	%
Net state taxes	0.3		1.7		0.7
Tax credits	(0.6)		(0.7)		(0.4)
Company-owned life insurance	(0.9)		(1.0)		(1.9)

Amortization of excess deferred taxes	(4.9)		(1.3)		(1.2)
All other differences	(1.3)		(1.4)		(0.5)
Effective income tax rate	13.6	%	18.3	%	17.7	%

Deferred tax assets and liabilities consist of the following:


	December 31,
(Thousands of dollars)	2021		2020
Deferred tax assets:
Deferred income taxes for future amortization of ITC and excess deferred taxes	$	101,133	$	104,314
Employee benefits	(4,671)		4,806
Federal net operating losses	59,119		—
Deferred payroll taxes	892		1,810
Other	6,777		7,790
Valuation allowance	(22)		(22)
	163,228		118,698
Deferred tax liabilities:
Property-related items, including accelerated depreciation	703,374		680,294
Regulatory balancing accounts	77,818		4,205

Debt-related costs	2,277		2,585
Other	18,587		12,714
	802,056		699,798
Net deferred tax liabilities	$	638,828	$	581,100

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:


	December 31,
(Thousands of dollars)	2021		2020
Unrecognized tax benefits at beginning of year	$	1,793	$	1,056
Gross increases – tax positions in prior period	310		506
Gross decreases – tax positions in prior period	—		—
Gross increases – current period tax positions	259		231
Gross decreases – current period tax positions	—		—
Settlements	—		—
Lapse in statute of limitations	—		—
Unrecognized tax benefits at end of year	$	2,362	$	1,793

In assessing whether uncertain tax positions should be recognized in its financial statements, management first determines whether it is more-likely-than-not that a tax position will be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. In evaluations of whether a tax position has met the more-likely-than-not recognition threshold, management presumes that the position will be examined by the appropriate taxing authority that would have full knowledge of all relevant information. For tax positions that meet the more-likely-than-not recognition threshold, management measures the amount of benefit recognized in the financial statements at the largest amount of benefit that is greater than 50% likely of being realized upon ultimate settlement. Unrecognized tax benefits are recognized in the first financial reporting period in which information becomes available indicating that such benefits will more-likely-than-not be realized. For each reporting period, management applies a consistent methodology to measure unrecognized tax benefits, and all unrecognized tax benefits are reviewed periodically and adjusted as circumstances warrant. Measurement of

unrecognized tax benefits is based on management’s assessment of all relevant information, including prior audit experience, the status of audits, conclusions of tax audits, lapsing of applicable statutes of limitation, identification of new issues, and any administrative guidance or developments.

At December 31, 2021, the total amount of unrecognized tax benefits that, if recognized, would impact the effective tax rate was $2.6 million for the Company and $2.4 million for Southwest. No significant increases or decreases in unrecognized tax benefits are expected within the next 12 months.

The Company and Southwest recognize interest expense and income and penalties related to income tax matters in income tax expense. There was $21,000 and $523,000 of tax-related interest income for 2021 and 2020, respectively, and none in 2019.

The Company’s regulated operations accounting for income taxes is impacted by the FASB’s Accounting Standards Codification (“ASC”) Topic 980 – Regulated Operations. Reductions in accumulated deferred income tax balances due to the reduction in the corporate income tax rates to 21% under the provisions of the Tax Cuts and Jobs Act (the “TCJA”), enacted in December 2017, may continue to result in a refund of excess deferred taxes to customers, generally through reductions in future rates. The TCJA included provisions that stipulate how these excess deferred taxes may be passed back to customers for certain accelerated tax depreciation benefits. The December 31, 2021 Consolidated Balance Sheets of Southwest and the Company reflect the impact of the TCJA and the remaining unamortized balance of the regulatory liability (including a gross-up), barring further changes to income tax rates. See also Note 5 - Regulatory Assets and Liabilities.

The Company and its subsidiaries file a consolidated federal income tax return in the U.S. and in various states, as well as separate returns in Canada. With few exceptions, the Company is no longer subject to U.S. federal, state and local, or Canadian income tax examinations for years before 2017.

The Company and each of its subsidiaries, including Southwest, participate in a tax sharing agreement to establish the method for allocating tax benefits and losses among members of the consolidated group. The consolidated federal income tax is apportioned among the subsidiaries using a separate return method.

The acquisition of Questar Pipelines by the Company was a taxable transaction for U.S. federal and state income tax purposes. As a result, the Company obtained a step-up in the basis of the assets acquired (as determined for income tax purposes), without succeeding to the holding period, accounting methods, or historical income tax liabilities associated with Questar Pipelines. Accordingly, the deferred income taxes were redetermined on the date of acquisition, December 31, 2021.

At December 31, 2021, the Company has a U.S. federal net operating loss carryforward of $449 million. The Company has no general business credit carryforwards. The Company has a net capital loss carryforward of $97,000, which will begin to expire in 2022. At December 31, 2021, the Company has an income tax net operating loss carryforward related to Canadian operations of $28.5 million, which begins to expire in 2034. As of the same date, the Company has $197.6 million of state net operating loss carryforwards. Depending on the jurisdiction in which the state net operating loss was generated, the carryforwards will begin to expire in 2025.

Management intends to continue to permanently reinvest any future foreign earnings in Canada.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

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+ Details

Segment Information

12 Months Ended

Dec. 31, 2021

Segment Reporting [Abstract]

Segment Information

Note 13 - Segment Information

The Company’s operating segments are determined based on the nature of their activities. The natural gas distribution segment is engaged in the business of purchasing, distributing, and transporting natural gas. Revenues are generated from the distribution and transportation of natural gas. The utility infrastructure services segment is primarily engaged in the business of providing gas and electric providers installation, replacement, repair, and maintenance of energy networks. Although the utility infrastructure services operations are geographically dispersed, they are aggregated and reported as a single segment as each reporting unit has similar economic characteristics. Over 99% of the total Company’s long-lived assets are in the U.S.

As a result of the Questar Pipelines acquisition on December 31, 2021, management updated its segment reporting from the historical presentation of two reportable segments to three reportable segments, with Questar Pipelines presented as the pipeline and storage segment. Given that the acquisition occurred on the last day of the year, the Company will begin reporting pipeline and storage segment activity/elements of earnings in 2022, and has reflected the segment assets in the table below. Refer to Note 15 - Business Acquisitions for additional information for the assets acquired as part of the Questar Pipelines acquisition.

The accounting policies of the reported segments are the same as those described within Note 1 - Background, Organization, and Summary of Significant Accounting Policies. Centuri accounts for the services provided to Southwest at contractual prices at contract inception. Accounts receivable for these services, which are not eliminated during consolidation, are presented in the table below:


	December 31,
(Thousands of dollars)	2021		2020
Accounts receivable for Centuri services	$	15,166	$	13,956

The following table presents the amount of revenues for both the natural gas distribution and utility infrastructure services segments (legacy segments) by geographic area:


	December 31,
(Thousands of dollars)	2021		2020		2019
Revenues (a)
United States	$	3,411,018	$	3,057,041	$	2,893,201
Canada	269,433		241,832		226,716
Total	$	3,680,451	$	3,298,873	$	3,119,917

(a)Revenues are attributed to countries based on the location of customers.

The Company has three reportable segments in 2021: natural gas distribution, utility infrastructure services, and pipeline and storage. Southwest has a single reportable segment that is referred to herein as the natural gas distribution segment of the Company. In order to reconcile to net income as disclosed in the Consolidated Statements of Income, an Other column is included associated with impacts of corporate and administrative activities related to Southwest Gas Holdings, Inc. The financial information pertaining to each segment as of and for the three years ended December 31, 2021, 2020, and 2019 are as follows:


	Year Ended December 31, 2021
(Thousands of dollars)	Natural Gas Distribution		Utility Infrastructure Services		Pipeline and Storage		Other		Total
Revenues from external customers	$	1,521,790	$	2,056,315	$	—	$	—	$	3,578,105
Intersegment sales	—		102,346		—		—		102,346
Total	$	1,521,790	$	2,158,661	$	—	$	—	$	3,680,451
Interest income	$	5,113	$	—	$	—	$	—	$	5,113
Interest expense	$	97,560	$	20,999	$	—	$	639	$	119,198
Depreciation and amortization	$	253,398	$	117,643	$	—	$	—	$	371,041
Income tax expense	$	29,338	$	18,776	$	—	$	(8,466)	$	39,648
Segment net income	$	187,135	$	40,420	$	—	$	(26,776)	$	200,779
Segment assets	$	7,950,263	$	2,579,748	$	2,187,582	$	47,664	$	12,765,257
Capital expenditures	$	601,983	$	113,643	$	—	$	—	$	715,626


	Year Ended December 31, 2020
(Thousands of dollars)	Natural Gas Distribution		Utility Infrastructure Services		Other		Total
Revenues from external customers	$	1,350,585	$	1,813,429	$	—	$	3,164,014
Intersegment sales	—		134,859		—		134,859
Total	$	1,350,585	$	1,948,288	$	—	$	3,298,873
Interest income	$	4,015	$	—	$	—	$	4,015
Interest expense	$	101,148	$	9,269	$	1,060	$	111,477
Depreciation and amortization	$	235,295	$	96,732	$	—	$	332,027
Income tax expense	$	35,755	$	31,128	$	(1,130)	$	65,753
Segment net income	$	159,118	$	74,862	$	(1,656)	$	232,324
Segment assets	$	7,256,636	$	1,475,237	$	3,980	$	8,735,853
Capital expenditures	$	692,216	$	132,889	$	—	$	825,105


	Year Ended December 31, 2019
(Thousands of dollars)	Natural Gas Distribution		Utility Infrastructure Services		Other		Total
Revenues from external customers	$	1,368,939	$	1,592,252	$	—	$	2,961,191
Intersegment sales	—		158,726		—		158,726
Total	$	1,368,939	$	1,750,978	$	—	$	3,119,917
Interest income	$	6,356	$	—	$	—	$	6,356
Interest expense	$	95,026	$	14,086	$	114	$	109,226
Depreciation and amortization	$	215,620	$	87,617	$	—	$	303,237
Income tax expense	$	34,973	$	21,399	$	(349)	$	56,023
Segment net income	$	163,171	$	52,404	$	(1,639)	$	213,936
Segment assets	$	6,798,746	$	1,365,194	$	6,108	$	8,170,048
Capital expenditures	$	778,748	$	159,400	$	—	$	938,148

The Corporate and administrative activities for Southwest Gas Holdings, Inc. in 2021 include expenses incurred to acquire Questar Pipelines as well as shareholder activism costs, collectively net of tax impacts.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Redeemable Noncontrolling Interests

12 Months Ended

Dec. 31, 2021

Noncontrolling Interest [Abstract]

Redeemable Noncontrolling Interests

Note 14 - Redeemable Noncontrolling Interests

In connection with the acquisition of Linetec in November 2018, the previous owner retained a 20% equity interest in Linetec, the reduction of which is subject to certain rights based on the passage of time or upon the occurrence of certain triggering events. Effective January 2022, the Company, by means of Centuri, has the right, but not the obligation, to purchase at fair value (subject to a floor) a portion of the interest held by the noncontrolling party, and in incremental amounts each year thereafter. The shares subject to the election accumulate (if earlier elections are not made) such that 100% of the interest retained by the noncontrolling party is subject to the election beginning in 2024. If the Company does not exercise its rights at each or any of the specified intervals, the noncontrolling party has the ability, but not the obligation, to exit their investment retained, by requiring Centuri to purchase a similar portion of their interest up to the maximum cumulative amounts specified at each interval discussed above. The outstanding noncontrolling interest is not subject to minimum purchase provisions and, following the eligibility dates for the elections, they do not expire. The redemption price represents the greater of fair value of the ownership interest to be redeemed on the redemption date or a floor amount under the terms of the agreement. The Company has determined that this noncontrolling interest is a redeemable noncontrolling interest and, in accordance with SEC guidance, is classified as mezzanine equity (temporary equity) in the Company’s Consolidated Balance Sheets.

In November 2021, certain members of Riggs Distler management acquired a 1.42% interest in Drum, which is subject to certain rights based on the passage of time or upon the occurrence of certain triggering events. Effective January 2027 and each calendar year thereafter or upon the occurrence of certain trigger events, the Company, through Centuri, has the right, but not the obligation, to purchase all of the interest held by the noncontrolling party at fair value. If the Company does not exercise its rights in accordance with the timeline noted, or upon the occurrence of certain other triggering events, the noncontrolling party has the ability, but not the obligation, to exit their investment retained by requiring Centuri to purchase all of their outstanding

interest. The outstanding noncontrolling interest is not subject to minimum purchase provisions and, following the eligibility date for the election, they do not expire. The redemption price represents the fair value of the ownership interest to be redeemed on the redemption date under the terms of the agreement. A portion of the redeemable noncontrolling interest acquired was funded through promissory notes made to noncontrolling interest holders bearing interest at the prime rate plus 2%. The promissory notes are payable by the noncontrolling interest holders upon certain triggering events including, but not limited to, termination of employment or the redemption of any interest under the agreement. The promissory notes are recognized as a reduction to the Company’s stockholders’ equity. Additionally, the Company has determined that this noncontrolling interest is a redeemable noncontrolling interest and, in accordance with SEC guidance, is classified as mezzanine equity (temporary equity) in the Company’s Consolidated Balance Sheets.

Significant changes in the value of the total redeemable noncontrolling interests, above a floor established at the acquisition date, are recognized as they occur, and the carrying value is adjusted as necessary at each reporting date. The fair value is estimated using a market approach that utilizes certain financial metrics from guideline public companies of similar industry and operating characteristics. Based on the fair value model employed, the estimated redemption value of the Linetec redeemable noncontrolling interest increased by approximately $12 million during the year ended December 31, 2021. Adjustment to the redemption value also impacted retained earnings, as reflected in the Company’s Consolidated Statement of Equity, but did not impact net income.

The following depicts changes to the balances of the redeemable noncontrolling interests:


	Linetec		Drum		Total
(Thousands of dollars)
Balance, December 31, 2019	$	84,542	$	—	$	84,542
Net income attributable to redeemable noncontrolling interests	6,661		—		6,661
Redemption value adjustment	74,513		—		74,513
Balance, December 31, 2020	165,716		—		165,716
Redeemable noncontrolling interest acquired	—		12,562		12,562
Net income attributable to redeemable noncontrolling interests	6,416		7		6,423
Redemption value adjustment	12,016		—		12,016
Balance, December 31, 2021	$	184,148	$	12,569	$	196,717

Business Acquisitions

12 Months Ended

Dec. 31, 2021

Business Combination and Asset Acquisition [Abstract]

Business Acquisitions

Note 15 - Business Acquisitions

On August 27, 2021, the Company, through its subsidiary, led principally by Centuri, completed the acquisition of a privately held regional infrastructure services business (and all of its equity interests), Drum and its primary subsidiary, Riggs Distler, for $822.2 million in cash consideration, net of $1.9 million cash acquired, and also assumed a long-term financing lease obligation. In November 2021, certain members of Riggs Distler management acquired a 1.42% interest in Drum, as discussed in Note 14 - Redeemable Noncontrolling Interests above. Drum is now a majority owned subsidiary of the company.

The acquisition extended the utility infrastructure services operations in the northeastern region of the U.S. and provides additional opportunities for expansion of the amount of work Centuri performs for electric and gas utilities. Funding for the acquisition was provided by proceeds from Centuri’s new term loan facility, as described in Note 8 - Debt.

Assets acquired and liabilities assumed in the transaction were recorded at their acquisition date fair values. Transaction costs associated with the acquisition were expensed as incurred. The Company’s allocation of the purchase price was based on an evaluation of the appropriate fair values and represented management’s best estimate based on available data (including market data, data regarding customers of the acquired businesses, terms of acquisition-related agreements, analysis of historical and projected results, and other types of data). The analysis included consideration of types of intangibles that were acquired, including customer relationships, trade name, and backlog. The gross contractual receivable is $81 million, exclusive of $12 million representing specific customer accounts that were deemed uncollectible; the accounts receivable were further reduced by measurement period adjustments of $8.6 million. The customer relationships and trade name were valued utilizing a discounted cash flow method. Determining the fair values of these intangible assets is judgmental in nature and requires the use of significant estimates and assumptions, including the attrition rate and discount rate for the customer relationships intangible asset and the royalty rate and discount rate for the trade name intangible asset. Certain payments were estimated as of the acquisition date and were adjusted when amounts were finalized. Further adjustments may still occur. During the fourth quarter of 2021, Centuri recorded a reduction to the purchase price of $6.3 million related to working capital adjustments calculated 60 days post-acquisition, and recorded measurement period adjustments primarily related to valuation of intangible assets, deferred tax liability estimates, and other refinements, as reflected in the table below. Due to the estimations made, the final purchase accounting has not yet been completed, and further refinements may occur, including potential changes to income taxes.

The preliminary estimated fair values of assets acquired and liabilities assumed as of August 27, 2021, are as follows:


(Millions of dollars)	Acquisition Date		Measurement Period Adjustments		Revised Acquisition Date
Cash and cash equivalents	$	1.9	$	—	$	1.9
Accounts receivable	69.1		(8.6)		60.5
Contract assets	40.1		7.4		47.5
Income taxes receivable, net	0.7		—		0.7
Right of use assets under operating leases	1.5		—		1.5
Prepaid expenses	5.2		—		5.2
Property and equipment	118.1		1.2		119.3
Intangible assets	335.0		(31.5)		303.5
Goodwill	446.8		2.7		449.5
Total assets acquired	1,018.4		(28.8)		989.6

Trade and other payables	46.2		—		46.2
Finance lease obligations	27.5		1.2		28.7
Contract liabilities	12.7		—		12.7
Operating lease obligations	1.5		—		1.5
Other liabilities	5.3		(0.3)		5.0
Deferred tax liabilities	94.8		(23.4)		71.4
Total liabilities assumed and noncontrolling interest	188.0		(22.5)		165.5
Net assets acquired	$	830.4	$	(6.3)	$	824.1

The amounts allocated to major classes of intangibles are as follows:


(Thousands of dollars)	Estimated Fair Value		Estimated Weighted Average Useful Life in Years
Backlog	$	4,500	1
Trade name	60,000		15
Customer relationships	239,000		19
	$	303,500

The Company incurred and expensed acquisition costs of $14 million for the period ended December 31, 2021, which were included in Utility infrastructure services expenses on the Company’s Consolidated Statement of Income.

Goodwill consists of the value associated with the assembled workforce, consolidation of operations, and the estimated economic value attributable to future opportunities related to the transaction. As the business of Drum was deemed a stock purchase for tax purposes, only pre-acquisition goodwill of $76 million that was historically tax-deductible by Riggs Distler will continue to be deductible for tax purposes by the Company. The intangible assets other than goodwill are included in Other property and investments in the Company’s Consolidated Balance Sheets.

The unaudited pro forma financial information for the Riggs Distler acquisition is combined in a table below with the unaudited pro forma financial information related to the Questar Pipelines acquisition by Southwest Gas Holdings, Inc.

Actual results from operations for Riggs Distler, excluding transaction costs and interest expense on acquisition related debt incurred by Centuri, included in the Consolidated Statements of Income since the date of acquisition are as follows:


(Thousands of dollars)	December 31, 2021
Utility infrastructure services revenues	$	163,830
Net income attributable to Southwest Gas Holdings, Inc.	$	1,374

On December 31, 2021 Southwest Gas Holdings, Inc. completed the acquisition of Dominion Energy Questar Pipeline, LLC and related entities (“Questar Pipelines”), which resulted in Questar Pipelines becoming a wholly owned subsidiary of the Company. The total consideration of $1.576 billion consisted of a cash payment of $1.545 billion, transaction costs paid on behalf of the seller of $4.7 million, and preliminary post-closing adjustments of $25.9 million.

The acquisition further diversifies the Company’s business with an expansion of regulated interstate natural gas pipelines and underground storage services under FERC jurisdiction. The entities acquired expands the Company’s operations into the Rocky Mountain region including Utah, Wyoming, and western Colorado. The Company financed the purchase price of this acquisition with a $1.6 billion draw on December 31, 2021 under a 364-day delayed-draw term loan entered into in November 2021. See Note 8 - Debt for additional information.

The Company is currently performing a detailed valuation analysis of the assets and liabilities of the acquired entities. The assets acquired and liabilities assumed were measured at estimated fair value at the closing date. The Company’s allocation of the purchase price was based on an evaluation of the appropriate fair values and represents management’s best estimate based on available data. Transaction costs associated with the acquisition were expensed as incurred. The majority of the operations acquired are subject to FERC rate-regulation and therefore are accounted for pursuant to ASC 980, Regulated Operations. The fair values of Questar Pipelines’ assets and liabilities, subject to rate making and cost recovery provisions, provide revenues derived from costs of service, including a return on investment of assets and liabilities included in rate base. Accordingly, the carrying values of such assets and liabilities were deemed to approximate their fair values. The fair value of the Questar Pipelines assets and liabilities assumed that are not subject to the rate-regulation provisions discussed above include a 50% equity method investment, non-regulated property, plant and equipment, and long-term debt assumed; related fair values were determined using a market approach, income approach, or cost approach, as appropriate. The final purchase accounting has not yet been completed. Further refinement is expected to occur, including finalization of the post-closing payment amount and income taxes.

The preliminary estimated fair values of assets acquired and liabilities assumed as of December 31, 2021, are as follows (in millions of dollars):


Gas plant, net	$	1,047.4
Other property and investments	51.3
Cash and cash equivalents	17.6
Accounts receivable, net of allowances	26.6
Prepaid and other current assets	27.4
Deferred charges and other assets	31.1
Goodwill	986.2
Deferred income taxes	15.4
Total assets acquired	2,203.0

Long-term debt	449.7
Accounts payable	7.0
Deferred purchased gas costs	5.7
Customer deposits	3.2
Accrued general taxes	0.4
Accrued interest	4.7
Other current liabilities	14.5
Accumulated removal costs	56.6
Other deferred credits	85.6
Total liabilities assumed	627.4
Net assets acquired	$	1,575.6

The Company incurred acquisition costs of $18.5 million for the period ended December 31, 2021, which were included in Operations and maintenance expense on the Company’s Consolidated Statement of Income.

The excess of the purchase price over the estimated fair values of the identifiable assets acquired and liabilities assumed was recognized as goodwill at the closing date. The goodwill reflects the value associated with enhancing the Company’s regulated operations portfolio, the economic value attributable to future opportunities including opportunities through diversification and increased scale in customer growth, and strong regional demand for both natural and renewable natural gas in a stable regulatory environment. As the Questar Pipelines acquisition was treated as an asset acquisition for tax purposes, the $935.1 million tax-basis goodwill is expected to be deductible for tax purposes by the Company. Deferred taxes have been recorded for the difference between book and tax basis of goodwill.

The following unaudited pro forma financial information reflects the consolidated results of operations of the Company assuming the Riggs Distler and Questar Pipelines acquisitions had taken place on January 1, 2020. The most significant pro forma adjustments relate to: (i) reflecting approximately $48.7 million in transaction costs in the year ended December 31, 2020, and excluding such costs from the year ended December 31, 2021, and (ii) reflecting incremental interest expense of $48.4 million in 2021, and approximately $52.1 million in the comparable 2020 period. The pro forma financial information has been prepared for comparative purposes only, and is not intended to be indicative of what the Company’s results would have been had the acquisition occurred at the beginning of the periods presented or of the results which may occur in the future, for a number of reasons. The reasons include, but are not limited to, differences between the assumptions used to prepare the pro forma information, potential cost savings from operating efficiencies, nor the impact of incremental costs incurred in integrating the businesses. This information is preliminary in nature and subject to change based upon final purchase accounting adjustments.

Amounts below are in millions of dollars, except per share amounts.


	Unaudited
	Year Ended December 31,
	2021		2020
Total operating revenues	$	4,236	$	3,980
Net income attributable to Southwest Gas Holdings, Inc.	$	278	$	276
Basic earnings per share	$	4.70	$	4.93
Diluted earnings per share	$	4.69	$	4.93

No actual results from operations for Questar Pipelines are included in the Consolidated Statements of Income since the acquisition occurred on December 31, 2021.

Background, Organization, and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	Nature of Operations. This is a combined annual report of Southwest Gas Holdings, Inc. and its subsidiaries (the “Company”) and Southwest Gas Corporation and its subsidiaries (“Southwest” or the “natural gas distribution” segment). The notes to the consolidated financial statements apply to both entities. Southwest Gas Holdings, Inc., a Delaware corporation, is a holding company, owning all of the shares of common stock of Southwest, all of the shares of common stock of Centuri Group, Inc. (“Centuri” or the “utility infrastructure services” segment), and all of the membership interests in the newly acquired Dominion Energy Questar Pipeline, LLC and related entities through the newly formed entity, MountainWest Pipelines Holding Company (herein referred to interchangeably as “Questar Pipelines” or “MountainWest”). Questar Pipelines is a third segment, referred to as the “pipeline and storage” segment. Southwest was previously referred to as the natural gas operations segment; with the addition of the Questar Pipelines natural gas interstate transmission and storage services, Southwest, primarily consisting of intrastate natural gas service to customers, will be referred to as indicated above. In October 2021, the Company entered into an agreement with Dominion Energy Questar Corporation, a wholly owned subsidiary of Dominion Energy, Inc., to acquire all equity interests in Questar Pipelines. On December 31, 2021, the Company completed the acquisition of Questar Pipelines. As a result of the acquisition closing on December 31, 2021, the Company’s Consolidated Statements of Income and Consolidated Statements of Cash Flows do not reflect results of operations or operating activities of Questar Pipelines otherwise occurring during 2021. Subsequent to the completion of the acquisition, and as noted above, the Company formed MountainWest, a wholly owned subsidiary, owning all of the membership interests in Questar Pipelines. Questar Pipelines, and the businesses underlying it, will be renamed under the MountainWest branding in the first half of 2022. See Note 15 - Business Acquisitions for additional information. The acquired operations further diversify the Company’s business in the midstream sector, with an expansion of interstate natural gas pipelines and underground storage services, primarily composed of regulated operations under the jurisdiction of the Federal Energy Regulatory Commission (the “FERC”), thereby expanding natural gas transportation services into Utah, Wyoming, and Colorado. The total consideration for the acquisition was $1.576 billion, including transaction costs paid on behalf of the seller and an estimated post-closing payment. The Company initially financed the purchase of this acquisition with a $1.6 billion draw under the 364-day term loan entered into in November 2021. See Note 8 - Debt for more information. On March 1, 2022, the Company announced that its Board of Directors (the “Board”) determined to separate Centuri from Southwest Gas Holdings, Inc. and has authorized management to complete the separation within the next nine to twelve months. Management intends to evaluate various alternatives to determine the optimal structure to maximize stockholder value. Depending on the form the separation takes, it will likely be subject to a number of conditions. Southwest is engaged in the business of purchasing, distributing, and transporting natural gas for customers in portions of Arizona, Nevada, and California. Public utility rates, practices, facilities, and service territories of Southwest are subject to regulatory oversight. The timing and amount of rate relief can materially impact results of operations. Natural gas purchases and the timing of related recoveries can materially impact liquidity. Results for the natural gas distribution segment are higher during winter periods due to the seasonality incorporated in its regulatory rate structures. Centuri is a strategic utility infrastructure services company dedicated to partnering with North America’s gas and electric providers to build and maintain the energy network that powers millions of homes across the United States (“U.S.”) and Canada. Centuri derives revenue primarily from installation, replacement, repair, and maintenance of energy networks. Centuri operations are generally conducted under the business names of NPL Construction Co. (“NPL”), NPL Canada Ltd. (“NPL Canada”), New England Utility Constructors, Inc. (“Neuco”), Linetec Services, LLC (“Linetec”), and Riggs Distler & Company, Inc. (“Riggs Distler”). Utility infrastructure services activity is seasonal in many of Centuri’s operating areas. Peak periods are the summer and fall months in colder climate areas, such as the northeastern and midwestern U.S. and in Canada. In warmer climate areas, such as the southwestern and southeastern U.S., utility infrastructure services activity continues year round.
Basis of Presentation	Basis of Presentation. The Company follows accounting principles generally accepted in the United States (“U.S. GAAP”) in accounting for all of its businesses. Unless specified otherwise, all amounts are in U.S. dollars. Accounting for regulated operations conforms with U.S. GAAP as applied to rate-regulated companies and as prescribed by federal agencies and commissions of the various states in which the rate-regulated companies operate. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Consolidation	Consolidation. The accompanying financial statements are presented on a consolidated basis for Southwest Gas Holdings, Inc. and all subsidiaries and Southwest Gas Corporation and all subsidiaries as of December 31, 2021 (except those accounted for using the equity method as discussed below). All significant intercompany balances and transactions have been eliminated with the exception of transactions between Southwest and Centuri in accordance with accounting treatment for rate-regulated entities. Centuri, through its subsidiaries, holds a 50% interest in W.S. Nicholls Western Construction Ltd. (“Western”), a Canadian infrastructure services company that is a variable interest entity. Centuri determined that it is not the primary beneficiary of the entity due to a shared-power structure; therefore, Centuri does not consolidate the entity and has recorded its investment, and results related thereto, using the equity method. The investment in Western, related earnings, and dividends received from Western in 2021 and 2020 were not significant. Centuri’s maximum exposure to loss as a result of its involvement with Western was estimated at $12.6 million as of December 31, 2021. MountainWest, through its subsidiaries, holds a 50% noncontrolling interest in White River Hub, LLC, a FERC-regulated transporter of natural gas with facilities that connect with six interstate pipeline systems and a major processing plant in Colorado. As noted above, Questar Pipelines does not consolidate the entity and has recorded its investment using the equity method. The investment in White River Hub is approximately $25.6 million, the related proportional earnings and dividends for which are not expected to be significant to the Company. The investment is included in Other property and investments on the Company’s Consolidated Balance Sheet at December 31, 2021.
Fair Value Measurements	Fair Value Measurements. Certain assets and liabilities are reported at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. U.S. GAAP states that a fair value measurement should be based on the assumptions that market participants would use in pricing the asset or liability and establishes a fair value hierarchy that ranks the inputs used to measure fair value by their reliability. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to fair values derived from unobservable inputs (Level 3 measurements). Financial assets and liabilities are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement. The three levels of the fair value hierarchy are as follows: Level 1 – quoted prices (unadjusted) in active markets for identical assets or liabilities that a company has the ability to access at the measurement date. Level 2 – inputs other than quoted prices included within Level 1 that are observable for similar assets or liabilities, either directly or indirectly. Level 3 – unobservable inputs for the asset or liability. Unobservable inputs are used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at the measurement date. The Company primarily used quoted market prices and other observable market pricing information (exclusive of purchase accounting adjustments as noted in Note 15 - Business Acquisitions) in valuing cash and cash equivalents, long-term debt outstanding, and assets of the qualified pension plan and the postretirement benefits other than pensions required to be recorded and/or disclosed at fair value. The Company uses prices and inputs that are current as of the measurement date, and recognizes transfers between levels at either the actual date of an event or a change in circumstance that caused the transfer.
Net Utility Plant	Net Regulated Operations Plant. Net regulated operations plant includes gas plant at original cost, less the accumulated provision for depreciation and amortization, plus any unamortized balance of acquisition adjustments. Original cost generally includes contracted services, material, payroll, and related costs such as taxes and certain benefits, general and administrative expenses, and an allowance for funds used during construction, less contributions in aid of construction.
Intangible Assets	Intangible Assets. Intangible assets (other than goodwill) are amortized using the straight-line method to reflect the pattern of economic benefits consumed over the estimated periods benefited. The recoverability of intangible assets is evaluated when events or circumstances indicate that a revision of estimated useful lives is warranted or that an intangible asset may be impaired. These intangible assets are included in Other property and investments on the Company’s Consolidated Balance Sheets.
Cash and Cash Equivalents	Cash and Cash Equivalents. For purposes of reporting consolidated cash flows, cash and cash equivalents include cash on hand and financial instruments with original maturities of three months or less. Such investments are carried at cost, which approximates market value. Cash and cash equivalents of the Company include $20 million of money market fund investments at December 31, 2021, and an insignificant amount at December 31, 2020. The money market fund investments for Southwest were insignificant at both balance sheet dates. These investments fall within Level 2 of the fair value hierarchy, due to the asset valuation methods used by money market funds. Typical non-cash investing activities for the Company and Southwest include capital expenditures that were not paid as of year end that are included in accounts payable totaling approximately $19.4 million. Additionally for Southwest, non-cash investing activities include customer advances applied as contributions toward utility construction activity, such amounts were not significant for the periods presented herein. Also, see Note 2 - Regulated Operations Plant and Leases for information related to right-of-use (“ROU”) assets obtained in exchange for lease liabilities, which are non-cash investing and financing activities. ROU assets and lease liabilities are also subject to non-cash impacts as a result of other factors, such as lease terminations and modifications.
Income Taxes	Income Taxes. The asset and liability method of accounting is utilized for the recognition of income taxes. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are anticipated to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the enactment date. For regulatory and financial reporting purposes, investment tax credits (“ITC”) related to gas utility operations are deferred and amortized over the life of related fixed assets. As of December 31, 2021, the Company had cumulative book earnings of approximately $59 million in its foreign jurisdiction. Management previously asserted and continues to assert that all the earnings of Centuri’s Canadian subsidiaries will be permanently reinvested in Canada. As a result, no U.S. deferred income taxes have been recorded related to cumulative foreign earnings. The Financial Accounting Standards Board (the “FASB”) issued guidance to allow an accounting policy election of either (i) treating taxes attributable to future taxable income related to Global Intangible Low-Taxed Income (“GILTI”) as a current period expense when incurred or (ii) recognizing deferred taxes for temporary differences expected to reverse as GILTI in future years. The Company has elected to treat GILTI as a current period cost when incurred and has considered the estimated 2021 GILTI impact, which was immaterial, to its 2021 tax expense.
Deferred Purchased Gas Costs	Deferred Purchased Gas Costs. The various regulatory commissions have established procedures to enable the rate-regulated companies to adjust billing rates for changes in the cost of natural gas purchased. The difference between the current cost of gas purchased and the cost of gas recovered in billed rates is deferred. Generally, these deferred amounts are recovered or refunded within one year. In mid-February 2021, the central U.S. (from south Texas to North Dakota and the eastern Rocky Mountains) experienced extreme cold temperatures, which increased natural gas demand and caused supply issues due to wellhead freeze-offs, power outages, or other adverse operating conditions upstream of Southwest’s distribution systems. These conditions caused daily natural gas prices to reach unprecedented levels. During this time, Southwest secured natural gas supplies, albeit at substantially higher prices, maintaining service to its customers. The incremental cost for these supplies was approximately $250 million, funded using a 364-day $250 million term loan executed in March 2021 (see Note 8 - Debt). The incremental gas costs were included, for collection from customers, as part of the purchased gas adjustment (“PGA”) mechanisms.
Prepaids and Other Current Assets	Prepaid and other current assets. Prepaid and other current assets for Southwest and the Company include, among other things, accrued purchased gas costs of $52 million in 2021 and $29 million in 2020, and gas pipe materials and operating supplies of $62.9 million in 2021 and $50 million in 2020 (carried at weighted average cost). Additionally, at the Company, there was $4.5 million in gas pipe materials and operating supplies in 2021 relating to Questar Pipelines, for a total of $67.4 million. In the third quarter of 2021, the Company and Southwest classified certain assets associated with its previous corporate headquarters as held for sale. As a result, the Company and Southwest reclassified approximately $31 million from Net regulated operations plant to Prepaid and other current assets on their respective Consolidated Balance Sheets during the third quarter of 2021; this was a non-cash item and therefore did not impact the Company’s or Southwest’s respective Consolidated Statements of Cash Flows.
Goodwill	Goodwill. As required by U.S. GAAP, goodwill is assessed for impairment annually, or more frequently, if circumstances indicate impairment to the carrying value of goodwill may have occurred. The goodwill impairment analysis was conducted as of October 1st using a qualitative assessment, as permitted by U.S. GAAP. Management of the Company and Southwest considered its reporting units and segments and determined that they remained consistent between periods presented below, and that no change was necessary with regard to the level at which goodwill is assessed for impairment.
Other Current Liabilities	Other Current Liabilities. Management recognizes in its balance sheets various liabilities that are expected to be settled through future cash payment within the next twelve months, including certain regulatory liabilities (refer to Note 5 - Regulatory Assets and Liabilities), customary accrued expenses for employee compensation and benefits, and declared but unpaid dividends.
Accumulated Removal Costs	Accumulated Removal Costs. Approved regulatory practices allow Southwest and Questar Pipelines to include in depreciation expense a component intended to recover removal costs associated with regulated operations plant retirements. In accordance with the Securities and Exchange Commission (“SEC”) position on presentation of these amounts, management reclassifies estimated removal costs from Accumulated depreciation to Accumulated removal costs within the liabilities section of the Consolidated Balance Sheets. Management regularly updates the estimated accumulated removal costs as amounts fluctuate between periods depending on the level of replacement work performed (and actual cost experience) compared to the estimated cost of removal in rates.
Gas Operating Revenues	Gas Operating Revenues. Southwest recognizes revenue when it satisfies its performance by transferring gas to the customer. Natural gas is delivered and “consumed” by the customer simultaneously. Revenues are recorded when customers are billed. Customer billings are substantially based on monthly meter reads and include certain other charges assessed monthly, and are calculated in accordance with applicable tariffs and state and local laws, regulations, and related agreements. An estimate of the margin associated with natural gas service provided, but not yet billed, to residential and commercial customers from the latest meter read date to the end of the reporting period is also recognized as accrued utility revenue. Revenues also include the net impacts of margin tracker/decoupling accruals based on criteria in U.S. GAAP for rate-regulated entities associated with alternative revenue programs. All of Southwest’s service territories have decoupled rate structures, which are designed to eliminate the direct link between volumetric sales and revenue, thereby mitigating the impacts of unusual weather variability and conservation on margin. See Note 3 - Revenue. Utility Infrastructure Services Revenues. The majority of Centuri contracts are performed under unit-price contracts. Generally, these contracts state prices per unit of installation. Typical installations are accomplished in a few weeks or less. Revenues are recorded as installations are completed. Revenues are recorded for long-term fixed-price contracts in a pattern that reflects the transfer of control of promised goods and services to the customer over time. The amount of revenue recognized on fixed-price contracts is based on costs expended to date relative to anticipated final contract costs. Changes in job performance, job conditions, and final contract settlements are factors that influence management’s assessment of total contract value and the total estimated costs to complete those contracts. Revisions in estimates of costs and earnings during the course of work are reflected in the accounting period in which the facts requiring revision become known. If a loss on a contract becomes known or is anticipated, the entire amount of the estimated ultimate loss is recognized at that time in the financial statements. Some unit-price contracts contain caps that if encroached, trigger revenue and loss recognition similar to a fixed-price contract model. See Note 3 - Revenue. Intercompany Transactions. Centuri recognizes revenues generated from contracts with Southwest (see Note 13 - Segment Information). The accounts receivable balance, revenues, and associated profits are included in the consolidated financial statements of the Company and Southwest and were not eliminated during consolidation in accordance with accounting treatment for rate-regulated entities. Utility Infrastructure Services Expenses. Centuri’s utility infrastructure services expenses in the Consolidated Statements of Income includes payroll expenses, office and equipment rental costs, subcontractor expenses, training, job-related materials, gains and losses on equipment sales, and professional fees. Net Cost of Gas Sold. Components of net cost of gas sold include natural gas commodity costs (fixed-price and variable-rate), pipeline capacity/transportation costs, and actual settled costs of natural gas derivative instruments, where relevant. Also included are the net impacts of PGA deferrals and recoveries, which by their inclusion, result in net cost of gas sold overall that is comparable to amounts included in billed gas operating revenues. Differences between amounts incurred with suppliers, transmission pipelines, etc. and amounts already included in customer rates, are temporarily deferred in PGA accounts pending inclusion in customer rates.
Operations and Maintenance Expense	Operations and Maintenance Expense. Operations and maintenance expense includes Southwest’s operating and maintenance costs associated with serving utility customers and maintaining its distribution and transmission systems, uncollectible customer accounts expense, administrative and general salaries and expense, employee benefits expense excluding relevant non-service cost components, and legal expense (including injuries and damages).
Depreciation and Amortization	Depreciation and Amortization. Regulated operations plant depreciation is computed on the straight-line remaining life method at composite rates considered sufficient to amortize costs over estimated service lives, including components which compensate for removal costs (net of salvage value), and retirements, as approved by the appropriate regulatory agency. When plant is retired from service, the original cost of plant, including cost of removal, less salvage, is charged to the accumulated provision for depreciation. See also discussion regarding Accumulated Removal Costs above. Other regulatory assets, including acquisition adjustments, are amortized when appropriate, over time periods authorized by regulators. Non-regulated operations, including utility infrastructure services-related property and equipment are depreciated on a straight-line method based on the estimated useful lives of the related assets. Costs and gains related to refunding regulated operations debt and debt issuance expenses are deferred and amortized over the weighted-average lives of the new issues and become a component of interest expense.
Allowance for Funds Used During Construction ("AFUDC")	Allowance for Funds Used During Construction (“AFUDC”). AFUDC represents the cost of both debt and equity funds used to finance regulated operations plant construction. AFUDC is capitalized as part of the cost of regulated operations plant. The debt portion of AFUDC is reported in the Company’s and Southwest’s Consolidated Statements of Income as an offset to Net interest deductions and the equity portion is reported as Other income.
Derivatives	Derivatives. In managing its natural gas supply portfolios, Southwest has historically entered into fixed- and variable-price contracts, which qualify as derivatives. Additionally, Southwest previously utilized fixed-for-floating swap contracts (“Swaps”) to supplement its fixed-price contracts. The fixed-price contracts, firm commitments to purchase a fixed amount of gas in the future at a fixed price, qualify for the normal purchases and normal sales exception that is allowed for contracts that are probable of delivery in the normal course of business, and are exempt from fair value reporting. The variable-price contracts qualify as derivative instruments; however, because the contract price is the prevailing price at the future transaction date, no fair value adjustment is required. In consultation with its regulators, management does not currently anticipate entering into new Swaps in the near term; the remaining Swaps matured in October 2020. Southwest does not utilize derivative financial instruments for speculative purposes, nor does it have trading operations.
Foreign Currency Translation	Foreign Currency Translation. Foreign currency-denominated assets and liabilities of consolidated subsidiaries are translated into U.S. dollars at exchange rates existing at the respective balance sheet dates. Translation adjustments resulting from fluctuations in exchange rates are recorded as a separate component of accumulated other comprehensive income within stockholders’ equity. Results of operations of foreign subsidiaries are translated using the monthly weighted-average exchange rates during the respective periods. Gains and losses resulting from foreign currency transactions are included in Other income and (expenses) of the Company. Gains and losses resulting from intercompany foreign currency transactions that are of a long-term investment nature are reported in Other comprehensive income, if applicable.
Earnings Per Share	Earnings Per Share. Basic earnings per share (“EPS”) in each period of this report were calculated by dividing net income attributable to Southwest Gas Holdings, Inc. by the weighted-average number of shares during those periods. Diluted EPS includes additional weighted-average common stock equivalents (performance shares and restricted stock units). Unless otherwise noted, the term “Earnings Per Share” refers to Basic EPS.
Recently Accounting Standards Updates	Recent Accounting Standards Updates. Accounting pronouncements adopted in 2021: In December 2019, the FASB issued ASU 2019-12 “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes.” The update simplifies the accounting for income taxes by removing certain exceptions to the general principles, as well as improving consistent application in Topic 740 by clarifying and amending existing guidance. The Company and Southwest adopted the update in the first quarter of 2021, the impact of which was not material to the consolidated financial statements of the Company or Southwest. In October 2021, the FASB issued ASU 2021-08 “Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers.” The update amongst other amendments, improves the guidance related to the recognition and measurement of contract assets and liabilities acquired during a business acquisition. The Company and Southwest adopted the update early on a retrospective basis as of January 1, 2021, as permitted, and concluded the impact was not material to the consolidated financial statements of the Company or Southwest. See Note 15 - Business Acquisitions. Recently issued accounting pronouncements that will be effective in 2022: In March 2020, the FASB issued ASU 2020-04 “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting.” The update provides optional guidance for a limited time to ease the potential burden in accounting for, or recognizing the effects of, reference rate reform on financial reporting, including when modifying a contract (during the eligibility period covered by the update to the topic) to replace a reference rate affected by reference rate reform. The update applies only to contracts and hedging relationships that reference the London Interbank Offered Rate (“LIBOR”) or another reference rate expected to be discontinued due to reference rate reform. The guidance was eligible to be applied upon issuance on March 12, 2020, and can generally be applied through December 31, 2022, but to date, no further updates have occurred that would extend the optional guidance to the full tenor of LIBOR expiration dates occurring after 2022. Management will monitor the impacts this update might have on the Company’s and Southwest’s consolidated financial statements and disclosures, and will reflect such appropriately, in the event that the optional guidance is elected. See also LIBOR discussion in Note 8 - Debt. In August 2020, the FASB issued ASU 2020-06 “Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging— Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity.” The update, amongst other amendments, improves the guidance related to the disclosures and earnings per share for convertible instruments and contracts in an entity’s own equity. The update is effective for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years; early adoption was permitted. Management is evaluating the impacts this update might have on the Company’s consolidated financial statements and disclosures.
Subsequent Events	Subsequent Events. Management monitors events occurring after the balance sheet date and prior to the issuance of the financial statements to determine the impacts, if any, of events on the financial statements to be issued or disclosures to be made, and has reflected them where appropriate.
Receivables and Related Allowances	Business activity with respect to natural gas utility operations is conducted with customers located within the three-state region of Arizona, Nevada, and California. Southwest’s accounts receivable are short-term in nature, with billing due dates customarily not extending beyond one month, with customers’ credit worthiness assessed upon account creation by evaluation of other utility service or their credit file, and related payment history. Although Southwest seeks generally to minimize its credit risk related to utility operations by requiring security deposits from new customers, imposing late fees, and actively pursuing collection on overdue accounts, some accounts are ultimately not collected. Customer accounts are subject to collection procedures that vary by jurisdiction (late fee assessment, notice requirements for disconnection of service, and procedures for actual disconnection and/or reestablishment of service). After disconnection of service, accounts are customarily written off approximately two months after disconnection if the account remains inactive. Dependent upon the jurisdiction, reestablishment of service requires both payment of previously unpaid balances and additional deposit requirements. Provisions for uncollectible accounts are recorded monthly based on experience, consideration of current and expected future conditions, customer and rate composition, and write-off processes. They are included in the ratemaking process as a cost of service. The Nevada jurisdictions have a regulatory mechanism associated with the gas-cost-related portion of uncollectible accounts. Such amounts are deferred and collected through a surcharge in the ratemaking process. Southwest lifted the moratorium on disconnection of natural gas service for non-payment in Arizona and Nevada in September 2021, which was initiated (at the same time as a moratorium on late fees) in March 2020 in response to the COVID-19 pandemic. The moratorium on disconnection in California ended in November 2021. Southwest recommenced assessing late fees on past-due balances in Arizona and Nevada in April 2021, and in California in August 2021. Southwest is actively working with customers experiencing financial hardship by means of flexible payment options, partnering with assistance agencies and participating in state funded arrearage payment assistance programs. Management continues to monitor expected credit losses in light of the impact of COVID-19. The allowance as of December 31, 2021 reflects the expected impact from the pandemic on balances as of that date, including consideration of customers’ current and future ability to pay those amounts that are due. MountainWest’s accounts receivable are also short-term with billing due dates customarily not extending beyond one month. Accounts receivable acquired in the Questar Pipelines acquisition were recorded at their estimated realizable value on December 31, 2021. See Note 15 - Business Acquisitions for additional information. Utility infrastructure services accounts receivable are recorded at face amounts less an allowance for doubtful accounts. Centuri’s customers are generally investment-grade gas and electric utility companies for which Centuri has historically recognized an insignificant amount of write-offs. Centuri’s accounts receivable balances carry standard payment terms of up to 60 days. Centuri maintains an allowance that is estimated based on historical collection experience, current and estimated future economic and market conditions, and a review of the current status of each customer's accounts receivable balance. Account balances are monitored at least monthly, and are charged off against the allowance when management determines it is probable the balance will not be recovered. Centuri has not been significantly impacted, nor does it anticipate it will experience significant difficulty in collecting amounts due, given the nature of its customers, as a result of the current environment surrounding COVID-19.

Background, Organization, and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Other Property and Investments

Other property and investments on Southwest’s and the Company’s Consolidated Balance Sheets includes:


	December 31,
(Thousands of dollars)	2021		2020
Net cash surrender value of COLI policies	$	149,947	$	140,874
Other property	3,146		2,737
Total Southwest Gas Corporation	153,093		143,611
Non-regulated property, equipment, and intangibles	1,616,392		1,089,414
Non-regulated accumulated provision for depreciation and amortization	(512,343)		(422,741)
Other property and investments	59,337		23,961
Total Southwest Gas Holdings, Inc.	$	1,316,479	$	834,245

Summary of Intangible Assets

Centuri’s intangible assets (other than goodwill) have finite lives and are associated with businesses previously acquired (including Riggs Distler). The balances at December 31, 2021 and 2020, respectively, were as follows:


	December 31, 2021
(Thousands of dollars)	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Customer relationships	$	393,834	$	(42,886)	$	350,948
Trade name and trademarks	79,650		(7,093)		72,557
Customer contracts backlog	4,500		(1,500)		3,000
Total	$	477,984	$	(51,479)	$	426,505

	December 31, 2020
Customer relationships	$	154,757	$	(29,237)	$	125,520
Trade name and trademarks	23,618		(8,954)		14,664
Customer contracts backlog	270		(270)		—
Noncompete agreements	1,931		(1,931)		—
Total	$	180,576	$	(40,392)	$	140,184

Schedule of Estimated Future Amortization of Intangible Assets

The estimated future amortization of the intangible assets for the next five years and thereafter is as follows:


(Thousands of dollars)
2022	$	29,814
2023	26,814
2024	26,814
2025	26,769
2026	26,580
Thereafter	289,714
Total	$	426,505

Schedule of Goodwill

Goodwill in Southwest’s natural gas distribution segment and in all of the Company’s operations, is reflected in their Consolidated Balance Sheets as follows (and as applicable):


(Thousands of dollars)	Natural Gas Distribution		Utility Infrastructure Services		Pipeline and Storage		Total Company
Balance, December 31, 2019	$	10,095	$	332,928	$	—	$	343,023
Foreign currency translation adjustment	—		2,161		—		2,161
Balance, December 31, 2020	10,095		335,089		—		345,184
Additional goodwill from Riggs Distler acquisition	—		449,501		—		449,501
Additional goodwill from Questar Pipelines acquisition	—		—		986,179		986,179
Foreign currency translation adjustment	—		468		—		468
Balance, December 31, 2021	$	10,095	$	785,058	$	986,179	$	1,781,332

Schedule of Capitalized and Debt Portion of AFUDC

Regulated operations plant construction costs, including AFUDC, are recoverable as part of authorized rates through depreciation when completed projects are placed into operation, and general rate relief is requested and granted. AFUDC, disaggregated by type, included in the Company’s and Southwest’s Consolidated Statements of Income are presented in the table below:


(Thousands of dollars)	2021			2020			2019
AFUDC:
Debt portion	$	1,046		$	3,202		$	4,558
Equity portion	—			4,724			4,161
AFUDC capitalized as part of regulated operations plant	$	1,046		$	7,926		$	8,719
AFUDC rate	0.96		%	5.51		%	5.36		%

Schedule of Other Income (Deductions)

The following table provides the composition of significant items included in Other income (deductions) on the Consolidated Statements of Income:


(Thousands of dollars)	2021		2020		2019
Southwest Gas Corporation – natural gas distribution segment:
Change in COLI policies	$	8,800	$	9,200	$	17,400
Interest income	5,113		4,015		6,356
Equity AFUDC	—		4,724		4,161
Other components of net periodic benefit cost	(14,021)		(20,022)		(15,059)
Miscellaneous income and (expense)	(4,451)		(4,507)		(3,341)
Southwest Gas Corporation – total other income (deductions)	(4,559)		(6,590)		9,517
Utility infrastructure services segment:

Foreign transaction gain (loss)	(22)		(16)		546
Equity in earnings of unconsolidated investment – Western	226		80		439
Miscellaneous income and (expense)	863		(271)		(519)
Centuri – total other income (deductions)	1,067		(207)		466
Corporate and administrative	(7)		8		102
Consolidated Southwest Gas Holdings, Inc. - total other income (deductions)	$	(3,499)	$	(6,789)	$	10,085

Schedule of Earnings Per Share, Basic and Diluted

A reconciliation of the denominator used in Basic and Diluted EPS calculations is shown in the following table:


(In thousands)	2021	2020	2019
Weighted average basic shares	59,145	55,998	54,245
Effect of dilutive securities:
Management Incentive Plan shares	—	—	12
Restricted stock units (1)	114	78	55
Weighted average diluted shares	59,259	56,076	54,312

Regulated Operations Plant and Leases (Tables)

12 Months Ended

Dec. 31, 2021

Regulated Operations [Abstract]

Schedule of Net Utility Plant

Major classes of regulated operations plant and their respective balances as of December 31, 2021 and 2020 were as follows:


	December 31,				December 31,
(Thousands of dollars)	2021		2020		2021		2020
	Southwest Gas Holdings, Inc.*				Southwest Gas Corporation
Gas plant:
Storage	$	437,793	$	101,203	$	103,874	$	101,203
Transmission	1,917,529		400,657		397,590		400,657
Distribution	7,506,489		7,078,656		7,506,489		7,078,656
General	530,346		515,879		496,643		515,879
Software and software-related intangibles	380,372		270,883		380,372		270,883
Other	17,161		16,722		16,607		16,722
	10,789,690		8,384,000		8,901,575		8,384,000
Less: accumulated depreciation and amortization	(3,397,736)		(2,419,348)		(2,538,508)		(2,419,348)
Construction work in progress	202,068		211,429		183,485		211,429
Net regulated operations plant	$	7,594,022	$	6,176,081	$	6,546,552	$	6,176,081

*Southwest Gas Holdings, Inc. includes the regulated operations plant associated with the Questar Pipelines acquisition.

Schedule of Depreciation and Amortization Expense

Depreciation and amortization expense on gas plant, including intangibles, was as follows:


(Thousands of dollars)	2021		2020		2019
Depreciation and amortization expense	$	230,245	$	215,636	$	197,358

Schedule of Components of Lease Expense, and Supplemental Cash Flow Information Related to Leases

The components of lease expense were as follows:


(Thousands of dollars)	2021		2020		2019
Southwest:
Operating lease cost	$	1,021	$	1,251	$	1,531

Centuri:
Operating lease cost	15,279		14,294		12,235

Finance lease cost:
Amortization of ROU assets	2,138		140		137
Interest on lease liabilities	278		37		34
Total finance lease cost	2,416		177		171
Short-term lease cost	103,800		19,806		16,217
Total lease cost - Southwest Gas Holdings, Inc.	$	122,516	$	35,528	$	30,154

Supplemental cash flow information related to leases for the years ended December 31, 2021, 2020 and 2019 was as follows:


	2021
(Thousands of dollars)	Southwest		Centuri		Total
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	744	$	14,669	$	15,413
Operating cash flows from finance leases	—		278		278
Financing cash flows from finance leases	—		3,547		3,547

ROU assets obtained in exchange for lease obligations:
Operating leases	$	609	$	11,597	$	12,206
Finance leases	—		3,332		3,332


	2020
(Thousands of dollars)	Southwest		Centuri		Total
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	766	$	12,889	$	13,655
Operating cash flows from finance leases	—		36		36
Financing cash flows from finance leases	—		199		199

ROU assets obtained in exchange for lease obligations:
Operating leases	$	1,547	$	19,372	$	20,919
Finance leases	—		361		361


	2019
(Thousands of dollars)	Southwest		Centuri		Total
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	1,278	$	11,166	$	12,444
Operating cash flows from finance leases	—		33		33
Financing cash flows from finance leases	—		212		212

ROU assets obtained in exchange for lease obligations:
Operating leases	$	862	$	23,825	$	24,687
Finance leases	—		13,839		13,839

Schedule of Supplemental Information Related to Leases Included in Balance Sheet

Supplemental information related to leases, including location in the Consolidated Balance Sheets, is as follows:


(Thousands of dollars)	December 31,
	2021			2020
Southwest:
Operating leases:
Net regulated operations plant	$	2,072		$	2,195

Other current liabilities	$	607		$	656
Other deferred credits and other long-term liabilities	1,500			1,586
Total operating lease liabilities	$	2,107		$	2,242

Weighted average remaining lease term (in years)	4.22			4.24
Weighted average discount rate	4.90		%	4.49		%

Centuri:
Operating leases:
Other property and investments	$	80,638		$	81,010

Other current liabilities	$	12,185		$	10,032
Other deferred credits and other long-term liabilities	72,930			75,247
Total operating lease liabilities	$	85,115		$	85,279

Finance leases:
Other property and investments	$	30,705		$	752

Other current liabilities	$	8,858		$	202
Other deferred credits and other long-term liabilities	20,585			490
Total finance lease liabilities	$	29,443		$	692

Weighted average remaining lease term (in years)
Operating leases	7.57			10.08
Finance leases	3.92			2.12

Weighted average discount rate
Operating leases	3.95		%	4.05		%
Finance leases	2.58		%	5.55		%

Schedule of Maturities of Operating Lease Liabilities

The following are schedules of maturities of lease liabilities as of December 31, 2021:


(Thousands of dollars)	Operating Leases
Southwest:
2022	$	639
2023	522
2024	499
2025	483
2026	220
Thereafter	—
Total lease payments	2,363
Less imputed interest	256
Total	$	2,107


(Thousands of dollars)	Operating Leases		Finance Leases
Centuri:
2022	$	15,200	$	9,494
2023	13,402		7,940
2024	11,321		6,476
2025	9,228		3,987
2026	7,878		2,108
Thereafter	45,529		1,008
Total lease payments	102,558		31,013
Less imputed interest	17,443		1,570
Total	$	85,115	$	29,443

Schedule of Maturities of Finance Lease Liabilities

The following are schedules of maturities of lease liabilities as of December 31, 2021:


(Thousands of dollars)	Operating Leases
Southwest:
2022	$	639
2023	522
2024	499
2025	483
2026	220
Thereafter	—
Total lease payments	2,363
Less imputed interest	256
Total	$	2,107


(Thousands of dollars)	Operating Leases		Finance Leases
Centuri:
2022	$	15,200	$	9,494
2023	13,402		7,940
2024	11,321		6,476
2025	9,228		3,987
2026	7,878		2,108
Thereafter	45,529		1,008
Total lease payments	102,558		31,013
Less imputed interest	17,443		1,570
Total	$	85,115	$	29,443

Revenue (Tables)

12 Months Ended

Dec. 31, 2021

Revenue from Contract with Customer [Abstract]

Summary of Revenue Disaggregated by Service Type and Contract Type


	December 31,
(Thousands of dollars)	2021		2020		2019
Residential	$	1,035,612	$	958,520	$	972,788
Small commercial	270,214		221,541		249,117
Large commercial	57,371		44,633		48,935
Industrial/other	42,313		26,242		22,074
Transportation	92,240		88,215		92,380
Revenue from contracts with customers	1,497,750		1,339,151		1,385,294
Alternative revenue program deferrals	13,181		12,140		(25,112)
Other revenues (a)	10,859		(706)		8,757
Total Gas operating revenues	$	1,521,790	$	1,350,585	$	1,368,939

The following tables display Centuri’s revenue from contracts with customers disaggregated by service type and contract type:


	December 31,
(Thousands of dollars)	2021		2020		2019
Service Types:
Gas infrastructure services	$	1,302,340	$	1,261,160	$	1,238,974
Electric power infrastructure services	525,202		411,826		247,717
Other	331,119		275,302		264,287
Total Utility infrastructure services revenues	$	2,158,661	$	1,948,288	$	1,750,978


	December 31,
(Thousands of dollars)	2021		2020		2019
Contract Types:
Master services agreement	$	1,652,978	$	1,490,009	$	1,383,377
Bid contract	505,683		458,279		367,601
Total Utility infrastructure services revenues	$	2,158,661	$	1,948,288	$	1,750,978

Unit price contracts	$	1,369,082	$	1,356,640	$	1,380,256
Fixed price contracts	267,742		157,701		112,924
Time and materials contracts	521,837		433,947		257,798
Total Utility infrastructure services revenues	$	2,158,661	$	1,948,288	$	1,750,978

Summary of Information about Receivables, Revenue Earned on Contracts in Progress in Excess of Billings, and Amounts Billed in Excess of Revenue Earned on Contracts


	December 31,
(Thousands of dollars)	2021		2020
Contracts receivable, net	$	296,005	$	278,316
Revenue earned on contracts in progress in excess of billings	214,774		96,996
Amounts billed in excess of revenue earned on contracts	11,860		4,507

Schedule of Utility Infrastructure Services Contracts Receivable

Utility infrastructure services contracts receivable consists of the following:


	December 31,
(Thousands of dollars)	2021		2020
Billed on completed contracts and contracts in progress	$	292,770	$	273,778
Other receivables	3,492		6,692
Contracts receivable, gross	296,262		280,470
Allowance for doubtful accounts	(257)		(2,154)
Contracts receivable, net	$	296,005	$	278,316

Receivables and Related Allowances (Tables)

12 Months Ended

Dec. 31, 2021

Receivables [Abstract]

Schedule of Accounts Receivable


	December 31,
(Thousands of dollars)	2021		2020
Gas utility customer accounts receivable balance	$	169,114	$	145,108

Schedule of Percent of Customers by State

The following table represents Southwest customers by state at December 31, 2021:


Percent of customers by state:
Arizona	53	%
Nevada	37	%
California	10	%

Schedule of Allowance for Uncollectibles

Southwest activity in the allowance account for uncollectibles is summarized as follows:


(Thousands of dollars)	Allowance for Uncollectibles
Balance, December 31, 2018	$	2,168
Additions charged to expense	3,507
Accounts written off, less recoveries	(3,580)
Balance, December 31, 2019	2,095
Additions charged to expense	4,693
Accounts written off, less recoveries	(2,454)
Balance, December 31, 2020	4,334
Additions charged to expense	5,415
Accounts written off, less recoveries	(6,490)
Balance, December 31, 2021	$	3,259

Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2021

Regulated Operations [Abstract]

Schedule of Regulatory Assets

The following table represents existing regulatory assets and liabilities:


	December 31,
	2021		2020		2021		2020
(Thousands of dollars)	Southwest Gas Holdings*				Southwest Gas Corporation
Regulatory assets:
Accrued pension and other postretirement benefit costs (1)	$	339,356	$	427,550	$	339,356	$	427,550

Deferred purchased gas costs (2)	291,145		2,053		291,145		2,053
Settled interest rate hedges (3)	31,278		—		—		—
Accrued purchased gas costs (4)	51,631		29,000		51,631		29,000
Unamortized premium on reacquired debt (5)	16,283		17,124		16,283		17,124
Accrued absence time (9)	16,975		15,565		16,975		15,565
Margin, interest- and tax-tracking (10)	22,709		4,759		22,709		4,759
Other (12)	62,233		45,596		60,798		45,596
	831,610		541,647		798,897		541,647
Regulatory liabilities:
Deferred purchased gas costs (2)	(5,736)		(54,636)		—		(54,636)
Accumulated removal costs (6)	(482,558)		(404,000)		(424,000)		(404,000)

Unamortized gain on reacquired debt (7)	(7,108)		(7,644)		(7,108)		(7,644)
Regulatory excess deferred/other taxes and gross-up (8)	(511,567)		(461,023)		(446,333)		(461,023)
Margin, interest- and property tax-tracking (10)	(8,523)		(17,132)		(8,523)		(17,132)
Unrecognized other postretirement benefit costs (11)	(17,815)		—		—		—
Other (12)	(10,321)		(3,503)		(8,573)		(3,503)
Net regulatory liabilities	$	(212,018)	$	(406,291)	$	(95,640)	$	(406,291)

*Southwest Gas Holdings, Inc. includes the regulatory assets and liabilities acquired as part of the Questar acquisition.

(1)Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovery period is greater than five years. (See Note 11 - Pension and Other Postretirement Benefits).

(2)Balance recovered or refunded on an ongoing basis with interest.

(4)Included in Prepaid and other current assets on the Consolidated Balance Sheets. Balance recovered or refunded on an ongoing basis.

(5)Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovered over life of debt instruments.

(7)Included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets. Amortized over life of debt instruments.

(9)Regulatory recovery occurs on a one-year lag basis through the labor loading process. Included in Prepaid and other current assets on the Consolidated Balance Sheets.


	December 31,
	2021		2020		2021		2020
(Thousands of dollars)	Southwest Gas Holdings				Southwest Gas Corporation
Other Regulatory Assets:
State mandated public purpose programs (including low income and conservation programs) (a) (e)	$	15,239	$	11,527	$	15,239	$	11,527
Infrastructure replacement programs and similar (b) (e)	6,545		7,731		6,545		7,731
Environmental compliance programs (c) (e)	6,807		5,235		6,807		5,235
Pension tracking mechanism (b)	10,281		3,075		10,281		3,075
Other (d)	23,361		18,028		21,926		18,028
	$	62,233	$	45,596	$	60,798	$	45,596

a)Included in Prepaid and other current assets on the Consolidated Balance Sheets.

b)Included in Deferred charges and other assets on the Consolidated Balance Sheets.

e)Balance recovered or refunded on an ongoing basis, generally with interest.


	December 31,
	2021		2020		2021		2020
(Thousands of dollars)	Southwest Gas Holdings				Southwest Gas Corporation
Other Regulatory Liabilities:
State mandated public purpose programs (including low income and conservation programs) (a) (c)	$	(1,886)	$	(834)	$	(1,886)	$	(834)
Environmental compliance programs (c) (d)	(4,182)		(405)		(4,182)		(405)

Other (b) (c)	(4,253)		(2,264)		(2,505)		(2,264)
	$	(10,321)	$	(3,503)	$	(8,573)	$	(3,503)

a)Included in Other current liabilities on the Consolidated Balance Sheets.

b)Included in Other deferred credits and other long-term liabilities, except $13,000 which is included included in Other current liabilities on the Consolidated Balance Sheets.

c)Balance typically recovered or refunded on an ongoing basis, generally with interest.

d)In 2021 and 2020, included in Other current liabilities on the Consolidated Balance Sheets.

Schedule of Regulatory Liabilities

The following table represents existing regulatory assets and liabilities:


	December 31,
	2021		2020		2021		2020
(Thousands of dollars)	Southwest Gas Holdings*				Southwest Gas Corporation
Regulatory assets:
Accrued pension and other postretirement benefit costs (1)	$	339,356	$	427,550	$	339,356	$	427,550

Deferred purchased gas costs (2)	291,145		2,053		291,145		2,053
Settled interest rate hedges (3)	31,278		—		—		—
Accrued purchased gas costs (4)	51,631		29,000		51,631		29,000
Unamortized premium on reacquired debt (5)	16,283		17,124		16,283		17,124
Accrued absence time (9)	16,975		15,565		16,975		15,565
Margin, interest- and tax-tracking (10)	22,709		4,759		22,709		4,759
Other (12)	62,233		45,596		60,798		45,596
	831,610		541,647		798,897		541,647
Regulatory liabilities:
Deferred purchased gas costs (2)	(5,736)		(54,636)		—		(54,636)
Accumulated removal costs (6)	(482,558)		(404,000)		(424,000)		(404,000)

Unamortized gain on reacquired debt (7)	(7,108)		(7,644)		(7,108)		(7,644)
Regulatory excess deferred/other taxes and gross-up (8)	(511,567)		(461,023)		(446,333)		(461,023)
Margin, interest- and property tax-tracking (10)	(8,523)		(17,132)		(8,523)		(17,132)
Unrecognized other postretirement benefit costs (11)	(17,815)		—		—		—
Other (12)	(10,321)		(3,503)		(8,573)		(3,503)
Net regulatory liabilities	$	(212,018)	$	(406,291)	$	(95,640)	$	(406,291)

*Southwest Gas Holdings, Inc. includes the regulatory assets and liabilities acquired as part of the Questar acquisition.

(1)Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovery period is greater than five years. (See Note 11 - Pension and Other Postretirement Benefits).

(2)Balance recovered or refunded on an ongoing basis with interest.

(4)Included in Prepaid and other current assets on the Consolidated Balance Sheets. Balance recovered or refunded on an ongoing basis.

(5)Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovered over life of debt instruments.

(7)Included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets. Amortized over life of debt instruments.

(9)Regulatory recovery occurs on a one-year lag basis through the labor loading process. Included in Prepaid and other current assets on the Consolidated Balance Sheets.


	December 31,
	2021		2020		2021		2020
(Thousands of dollars)	Southwest Gas Holdings				Southwest Gas Corporation
Other Regulatory Assets:
State mandated public purpose programs (including low income and conservation programs) (a) (e)	$	15,239	$	11,527	$	15,239	$	11,527
Infrastructure replacement programs and similar (b) (e)	6,545		7,731		6,545		7,731
Environmental compliance programs (c) (e)	6,807		5,235		6,807		5,235
Pension tracking mechanism (b)	10,281		3,075		10,281		3,075
Other (d)	23,361		18,028		21,926		18,028
	$	62,233	$	45,596	$	60,798	$	45,596

a)Included in Prepaid and other current assets on the Consolidated Balance Sheets.

b)Included in Deferred charges and other assets on the Consolidated Balance Sheets.

e)Balance recovered or refunded on an ongoing basis, generally with interest.


	December 31,
	2021		2020		2021		2020
(Thousands of dollars)	Southwest Gas Holdings				Southwest Gas Corporation
Other Regulatory Liabilities:
State mandated public purpose programs (including low income and conservation programs) (a) (c)	$	(1,886)	$	(834)	$	(1,886)	$	(834)
Environmental compliance programs (c) (d)	(4,182)		(405)		(4,182)		(405)

Other (b) (c)	(4,253)		(2,264)		(2,505)		(2,264)
	$	(10,321)	$	(3,503)	$	(8,573)	$	(3,503)

a)Included in Other current liabilities on the Consolidated Balance Sheets.

b)Included in Other deferred credits and other long-term liabilities, except $13,000 which is included included in Other current liabilities on the Consolidated Balance Sheets.

c)Balance typically recovered or refunded on an ongoing basis, generally with interest.

d)In 2021 and 2020, included in Other current liabilities on the Consolidated Balance Sheets.

Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss)


	Year Ended December 31,
	2021						2020						2019
(Thousands of dollars)	Before- Tax Amount		Tax (Expense) or Benefit (1)		Net-of- Tax Amount		Before- Tax Amount		Tax (Expense) or Benefit (1)		Net-of- Tax Amount		Before- Tax Amount		Tax (Expense) or Benefit (1)		Net-of- Tax Amount
Defined benefit pension plans:
Net actuarial gain/(loss)	$	59,176	$	(14,202)	$	44,974	$	(57,539)	$	13,809	$	(43,730)	$	(71,087)	$	17,061	$	(54,026)
Amortization of prior service cost	959		(230)		729		1,155		(277)		878		1,271		(305)		966
Amortization of net actuarial (gain)/loss	44,597		(10,703)		33,894		37,830		(9,079)		28,751		23,376		(5,610)		17,766
Prior service cost	—		—		—		—		—		—		(1,878)		452		(1,426)
Regulatory adjustment	(88,194)		21,167		(67,027)		7,435		(1,785)		5,650		36,944		(8,867)		28,077
Pension plans other comprehensive income (loss)	16,538		(3,968)		12,570		(11,119)		2,668		(8,451)		(11,374)		2,731		(8,643)
FSIRS (designated hedging activities):
Amounts reclassified into net income	2,174		(522)		1,652		3,247		(780)		2,467		3,344		(803)		2,541
FSIRS other comprehensive income (loss)	2,174		(522)		1,652		3,247		(780)		2,467		3,344		(803)		2,541
Total other comprehensive income (loss) –Southwest Gas Corporation	18,712		(4,490)		14,222		(7,872)		1,888		(5,984)		(8,030)		1,928		(6,102)
Foreign currency translation adjustments:
Translation adjustments	20		—		20		1,713		—		1,713		2,038		—		2,038
Foreign currency other comprehensive income (loss)	20		—		20		1,713		—		1,713		2,038		—		2,038
Total other comprehensive income (loss) – Southwest Gas Holdings, Inc.	$	18,732	$	(4,490)	$	14,242	$	(6,159)	$	1,888	$	(4,271)	$	(5,992)	$	1,928	$	(4,064)

Schedule of Rollforward of Accumulated Other Comprehensive Income

The following table represents a rollforward of AOCI, presented on the Company’s Consolidated Balance Sheets and its Consolidated Statements of Equity:


	Defined Benefit Plans						FSIRS						Foreign Currency Items
(Thousands of dollars)	Before-Tax		Tax (Expense) Benefit (4)		After-Tax		Before- Tax		Tax (Expense) Benefit (4)		After-Tax		Before- Tax		Tax (Expense) Benefit		After-Tax		AOCI
Beginning Balance AOCI December 31, 2020	$	(77,720)	$	18,653	$	(59,067)	$	(2,719)	$	651	$	(2,068)	$	132	$	—	$	132	$	(61,003)
Net actuarial gain/(loss)	59,176		(14,202)		44,974		—		—		—		—		—		—		44,974
Translation adjustments	—		—		—		—		—		—		20		—		20		20
Other comprehensive income before reclassifications	59,176		(14,202)		44,974		—		—		—		20		—		20		44,994
FSIRS amount reclassified from AOCI (1)	—		—		—		2,174		(522)		1,652		—		—		—		1,652
Amortization of prior service cost (2)	959		(230)		729		—		—		—		—		—		—		729
Amortization of net actuarial loss (2)	44,597		(10,703)		33,894		—		—		—		—		—		—		33,894

Regulatory adjustment (3)	(88,194)		21,167		(67,027)		—		—		—				—		—		(67,027)
Net current period other comprehensive income (loss) attributable to Southwest Gas Holdings, Inc.	16,538		(3,968)		12,570		2,174		(522)		1,652		20		—		20		14,242
Ending Balance AOCI December 31, 2021	$	(61,182)	$	14,685	$	(46,497)	$	(545)	$	129	$	(416)	$	152	$	—	$	152	$	(46,761)

(1)The FSIRS reclassification amount is included in Net interest deductions on the Company’s Consolidated Statements of Income.

(2)These AOCI components are included in the computation of net periodic benefit cost (see Note 11 - Pension and Other Postretirement Benefits for additional details).

(4) Tax amounts are calculated using a 24% rate.

The following table represents a rollforward of AOCI, presented on Southwest’s Consolidated Balance Sheets:


	Defined Benefit Plans						FSIRS
(Thousands of dollars)	Before-Tax		Tax (Expense) Benefit (9)		After- Tax		Before- Tax		Tax (Expense) Benefit (9)		After- Tax		AOCI
Beginning Balance AOCI December 31, 2020	$	(77,720)	$	18,653	$	(59,067)	$	(2,719)	$	651	$	(2,068)	$	(61,135)
Net actuarial gain/(loss)	59,176		(14,202)		44,974		—		—		—		44,974
Other comprehensive loss before reclassifications	59,176		(14,202)		44,974		—		—		—		44,974
FSIRS amount reclassified from AOCI (6)	—		—		—		2,174		(522)		1,652		1,652
Amortization of prior service cost (7)	959		(230)		729		—		—		—		729
Amortization of net actuarial loss (7)	44,597		(10,703)		33,894		—		—		—		33,894

Regulatory adjustment (8)	(88,194)		21,167		(67,027)		—		—		—		(67,027)
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation	16,538		(3,968)		12,570		2,174		(522)		1,652		14,222
Ending Balance AOCI December 31, 2021	$	(61,182)	$	14,685	$	(46,497)	$	(545)	$	129	$	(416)	$	(46,913)

(6) The FSIRS reclassification amount is included in Net interest deductions on Southwest’s Consolidated Statements of Income.

(7) These AOCI components are included in the computation of net periodic benefit cost (see Note 11 - Pension and Other Postretirement Benefits for additional details).

(9) Tax amounts are calculated using a 24% rate.

Schedule of Amount Recognized Before Income Tax in Accumulated Other Comprehensive Income

The following table represents amounts (before income tax impacts) included in AOCI (in the tables above), that have not yet been recognized in net periodic benefit cost:


	Year Ended December 31,
(Thousands of dollars)	2021		2020
Net actuarial loss	$	(399,010)	$	(502,783)
Prior service cost	(1,528)		(2,487)
Less: amount recognized in regulatory assets	339,356		427,550
Recognized in AOCI	$	(61,182)	$	(77,720)

Other Changes in Plan Assets and Benefit Obligations Recognized in Net Periodic Benefit Cost and Other Comprehensive Income


	Year Ended December 31,
	2021								2020								2019
(Thousands of dollars)	Total		Qualified Retirement Plan		SERP		PBOP		Total		Qualified Retirement Plan		SERP		PBOP		Total		Qualified Retirement Plan		SERP		PBOP
Net actuarial loss (gain) (a)	$	(59,176)	$	(54,892)	$	(3,245)	$	(1,039)	$	57,539	$	45,665	$	7,240	$	4,634	$	71,087	$	66,557	$	7,975	$	(3,445)
Amortization of prior service cost (b)	(959)		—		—		(959)		(1,155)		—		—		(1,155)		(1,271)		—		—		(1,271)
Amortization of net actuarial loss (b)	(44,597)		(41,955)		(2,642)		—		(37,830)		(36,025)		(1,805)		—		(23,376)		(22,356)		(1,020)		—
Prior service cost	—		—		—		—		—		—		—		—		1,878		—		—		1,878
Regulatory adjustment	88,194		86,196		—		1,998		(7,435)		(3,956)		—		(3,479)		(36,944)		(39,782)		—		2,838
Recognized in other comprehensive (income) loss	(16,538)		(10,651)		(5,887)		—		11,119		5,684		5,435		—		11,374		4,419		6,955		—
Net periodic benefit costs recognized in net income	57,397		51,194		4,599		1,604		56,291		50,583		3,798		1,910		42,465		36,982		3,046		2,437
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss	$	40,859	$	40,543	$	(1,288)	$	1,604	$	67,410	$	56,267	$	9,233	$	1,910	$	53,839	$	41,401	$	10,001	$	2,437

Common Stock (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Schedule of Common Stock Activity

The following table provides the life-to-date activity under the Equity Shelf Program for the period ended December 31, 2021:


Gross proceeds	$	158,180,343
Less: agent commissions	(1,581,803)
Net proceeds	$	156,598,540
Number of shares sold	2,302,407
Weighted average price per share	$	68.70

Debt (Tables)

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt


	December 31,
	2021				2020
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
(Thousands of dollars)
Southwest Gas Corporation:
Debentures:
Notes, 6.1%, due 2041	$	125,000	$	166,380	$	125,000	$	174,858
Notes, 3.875%, due 2022	250,000		250,603		250,000		258,825
Notes, 4.875%, due 2043	250,000		307,538		250,000		317,190
Notes, 3.8%, due 2046	300,000		329,055		300,000		347,046
Notes, 3.7%, due 2028	300,000		325,191		300,000		344,553
Notes, 4.15%, due 2049	300,000		342,030		300,000		370,278
Notes, 2.2%, due 2030	450,000		440,838		450,000		474,552
Notes 3.18%, due 2051	300,000		292,116		—		—
8% Series, due 2026	75,000		92,623		75,000		99,723
Medium-term notes, 7.78% series, due 2022	25,000		25,122		25,000		26,663
Medium-term notes, 7.92% series, due 2027	25,000		31,555		25,000		33,802
Medium-term notes, 6.76% series, due 2027	7,500		8,949		7,500		9,613
Unamortized discount and debt issuance costs	(19,959)				(17,822)
	2,387,541				2,089,678
Revolving credit facility and commercial paper	130,000		130,000		150,000		150,000
Industrial development revenue bonds:
Tax-exempt Series A, due 2028	50,000		50,000		50,000		50,000
2003 Series A, due 2038	50,000		50,000		50,000		50,000
2008 Series A, due 2038	50,000		50,000		50,000		50,000
2009 Series A, due 2039	50,000		50,000		50,000		50,000
Unamortized discount and debt issuance costs	(1,938)				(1,472)
	198,062				198,528
Less: current maturities	(275,000)				—
Southwest Gas Corporation total long-term debt, less current maturities	$	2,440,603			$	2,438,206
Southwest Gas Holdings, Inc.:
Centuri secured term loan facility	$	1,117,138	$	1,117,841	$	226,648	$	230,824
Centuri secured revolving credit facility	103,329		103,749		26,626		26,645
MountainWest unsecured senior notes, 3.53%, due in 2028	102,078		102,078		—		—
MountainWest unsecured senior notes, 4.875%, due in 2041	199,926		199,926		—		—
MountainWest unsecured senior notes, 3.91%, due in 2038	147,735		147,735		—		—
Other debt obligations	51,665		50,003		81,973		84,246
Unamortized discount and debt issuance costs	(24,466)				(820)
Less: current maturities	(22,324)				(40,433)
Southwest Gas Holdings, Inc. total long-term debt, less current maturities	$	4,115,684			$	2,732,200

Summary of Effective Interest Rates on Variable-Rate IDRBs

The effective interest rates on Southwest’s variable-rate IDRBs are included in the table below:


	December 31,
	2021		2020
2003 Series A	0.91	%	0.80	%
2008 Series A	0.90	%	0.83	%
2009 Series A	0.88	%	0.76	%
Tax-exempt Series A	0.92	%	0.87	%

Estimated Maturities of Long-Term Debt

Estimated maturities of long-term debt for the next five years are:


(Thousands of dollars)	2022		2023		2024		2025		2026		Total
Southwest Gas Corporation:
Debentures	$	275,000	$	—	$	—	$	—	$	75,000	$	350,000
Revolving credit facility and commercial paper	—		—		—		130,000		—		130,000
Total	275,000		—		—		130,000		75,000		480,000
Southwest Gas Holdings, Inc.:
Centuri secured term loan facility	11,450		11,450		11,450		11,450		11,450		57,250
Centuri secured revolving credit facility	—		—		—		—		103,329		103,329
Other debt obligations	10,874		11,047		11,285		9,076		7,490		49,772
Total	$	297,324	$	22,497	$	22,735	$	150,526	$	197,269	$	690,351

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24072-122690

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28541-108399

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495743-112612

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21538-112644

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=123599511&loc=d3e64711-112823

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21475-112644

+ Details

Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Share-Based Plan Compensation Expense, Including Cash Award

The table below shows total share-based plan compensation expense which was recognized in the Consolidated Statements of Income:


	Year Ended December 31,
(Thousands of dollars)	2021		2020		2019
Share-based compensation plan expense, net of related tax benefits	$	5,747	$	4,816	$	5,154
Share-based compensation plan related tax benefits	1,815		1,521		1,627

Schedule of Nonvested Performance and Restricted Stock Unit Plans

The following table summarizes the activity of the restricted stock/units programs as of December 31, 2021:


(Thousands of shares)	Restricted Stock/ Units (1)	Weighted- average grant date fair value
Nonvested/unissued at December 31, 2020	401	$	62.23
Granted	188	65.38
Dividends	10
Forfeited or expired	(9)	70.09
Vested and issued (2)	(70)	69.87
Nonvested/unissued at December 31, 2021	520	$	61.01

(2)Includes shares for retiree payouts and those converted for taxes.

Pension and Other Postretirement Benefits (Tables)

12 Months Ended

Dec. 31, 2021

Retirement Benefits [Abstract]

Schedule of Assumptions Used

The rates are presented in the table below:


	December 31,
	2021		2020
Discount rate	3.00	%	2.75	%
Weighted-average rate of compensation increase	3.25	%	3.00	%
Asset return assumption	6.50	%	6.50	%

Schedule of Defined Benefit Plans Disclosures

The following table sets forth the retirement plan, SERP, and PBOP funded statuses and amounts recognized on the Consolidated Balance Sheets and Consolidated Statements of Income.


	Year Ended December 31,
	2021									2020
(Thousands of dollars)	Qualified Retirement Plan			SERP			PBOP			Qualified Retirement Plan			SERP			PBOP
Change in benefit obligations:
Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO)	$	1,499,239		$	53,631		$	82,205		$	1,329,577		$	47,397		$	76,111
Service cost	41,159			526			1,691			34,299			389			1,581
Interest cost	40,432			1,431			2,193			45,555			1,604			2,582

Actuarial loss (gain)	8,908			(3,244)			3,438			145,440			7,240			6,547
Benefits paid	(58,541)			(2,814)			(5,301)			(55,632)			(2,999)			(4,616)
Benefit obligation at end of year (PBO/PBO/APBO)	1,531,197			49,530			84,226			1,499,239			53,631			82,205
Change in plan assets:
Market value of plan assets at beginning of year	1,186,433			—			52,286			974,993			—			52,838
Actual return on plan assets	136,151			—			7,717			165,072			—			5,320
Employer contributions	102,000			2,814			—			102,000			2,999			—
Benefits paid	(58,541)			(2,814)			(7,835)			(55,632)			(2,999)			(5,872)
Market value of plan assets at end of year	1,366,043			—			52,168			1,186,433			—			52,286
Funded status at year end	$	(165,154)		$	(49,530)		$	(32,058)		$	(312,806)		$	(53,631)		$	(29,919)
Weighted-average assumptions (benefit obligation):
Discount rate	3.00		%	3.00		%	3.00		%	2.75		%	2.75		%	2.75		%
Weighted-average rate of compensation increase	3.25		%	3.25		%	N/A			3.00		%	3.00		%	N/A

Schedule of Accumulated Benefit Obligation

The accumulated benefit obligation for the retirement plan and the SERP is presented below:


	December 31,
(Thousands of dollars)	2021		2020
Retirement plan	$	1,395,773	$	1,367,179
SERP	46,885		50,471

Schedule of Expected Benefit Payments

Benefits expected to be paid for pension, SERP, and PBOP over the next 10 years are as follows:


(Millions of dollars)	2022		2023		2024		2025		2026		2027-2031
Pension	$	62.0	$	64.0	$	65.0	$	67.0	$	68.0	$	365.0
SERP	3.0		3.0		3.0		3.0		2.9		13.9
PBOP	5.0		5.2		5.2		5.2		5.3		27.3

Schedule of Net Benefit Cost

Components of net periodic benefit cost:


	Qualified Retirement Plan						SERP						PBOP
(Thousands of dollars)	2021		2020		2019		2021		2020		2019		2021		2020		2019
Service cost	$41,159		$34,299		$25,864		$526		$389		$266		$1,691		$1,581		$1,276
Interest cost	40,432		45,555		49,006		1,431		1,604		1,760		2,193		2,582		3,046
Expected return on plan assets	(72,352)		(65,296)		(60,244)		—		—		—		(3,239)		(3,408)		(3,156)
Amortization of prior service cost	—		—		—		—		—		—		959		1,155		1,271
Amortization of net actuarial loss	41,955		36,025		22,356		2,642		1,805		1,020		—		—		—
Net periodic benefit cost	$51,194		$50,583		$36,982		$4,599		$3,798		$3,046		$1,604		$1,910		$2,437
Weighted-average assumptions (net benefit cost)
Discount rate	2.75	%	3.50	%	4.50	%	2.75	%	3.50	%	4.50	%	2.75	%	3.50	%	4.50	%
Expected return on plan assets	6.50	%	6.75	%	7.00	%	N/A		N/A		N/A		6.50	%	6.75	%	7.00	%
Weighted-average rate of compensation increase	3.00	%	3.25	%	3.25	%	3.00	%	3.25	%	3.25	%	N/A		N/A		N/A

Schedule of Amounts Recognized in Other Comprehensive Income

The following table represents amounts (before income tax impacts) included in AOCI (in the tables above), that have not yet been recognized in net periodic benefit cost:


	Year Ended December 31,
(Thousands of dollars)	2021		2020
Net actuarial loss	$	(399,010)	$	(502,783)
Prior service cost	(1,528)		(2,487)
Less: amount recognized in regulatory assets	339,356		427,550
Recognized in AOCI	$	(61,182)	$	(77,720)

Other Changes in Plan Assets and Benefit Obligations Recognized in Net Periodic Benefit Cost and Other Comprehensive Income


	Year Ended December 31,
	2021								2020								2019
(Thousands of dollars)	Total		Qualified Retirement Plan		SERP		PBOP		Total		Qualified Retirement Plan		SERP		PBOP		Total		Qualified Retirement Plan		SERP		PBOP
Net actuarial loss (gain) (a)	$	(59,176)	$	(54,892)	$	(3,245)	$	(1,039)	$	57,539	$	45,665	$	7,240	$	4,634	$	71,087	$	66,557	$	7,975	$	(3,445)
Amortization of prior service cost (b)	(959)		—		—		(959)		(1,155)		—		—		(1,155)		(1,271)		—		—		(1,271)
Amortization of net actuarial loss (b)	(44,597)		(41,955)		(2,642)		—		(37,830)		(36,025)		(1,805)		—		(23,376)		(22,356)		(1,020)		—
Prior service cost	—		—		—		—		—		—		—		—		1,878		—		—		1,878
Regulatory adjustment	88,194		86,196		—		1,998		(7,435)		(3,956)		—		(3,479)		(36,944)		(39,782)		—		2,838
Recognized in other comprehensive (income) loss	(16,538)		(10,651)		(5,887)		—		11,119		5,684		5,435		—		11,374		4,419		6,955		—
Net periodic benefit costs recognized in net income	57,397		51,194		4,599		1,604		56,291		50,583		3,798		1,910		42,465		36,982		3,046		2,437
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss	$	40,859	$	40,543	$	(1,288)	$	1,604	$	67,410	$	56,267	$	9,233	$	1,910	$	53,839	$	41,401	$	10,001	$	2,437

Schedule of Fair Value of Plan Assets


	December 31,
	2021						2020
(Thousands of dollars)	Qualified Retirement Plan		PBOP		Total		Qualified Retirement Plan		PBOP		Total
Assets at fair value:
Level 1 – Quoted prices in active markets for identical financial assets
Mutual funds	$	—	$	35,194	$	35,194	$	—	$	30,358	$	30,358
Total Level 1 Assets (1)	—		35,194		35,194		—		30,358		30,358
Level 2 – Significant other observable inputs
Private commingled equity funds (2)
Global	373,936		4,538		378,474		324,084		5,878		329,962
International	158,461		1,923		160,384		141,290		2,563		143,853
U.S. equity securities	279,062		3,386		282,448		223,374		4,051		227,425
Emerging markets	82,004		995		82,999		76,679		1,391		78,070
Private commingled fixed income funds (3)	463,942		5,630		469,572		412,230		7,476		419,706
Pooled funds and mutual funds	5,979		500		6,479		5,990		565		6,555
Government fixed income and mortgage backed securities	196		2		198		201		4		205
Total Level 2 assets (4)	1,363,580		16,974		1,380,554		1,183,848		21,928		1,205,776
Total Plan assets at fair value	1,363,580		52,168		1,415,748		1,183,848		52,286		1,236,134
Insurance company general account contracts (5)	2,463		—		2,463		2,585		—		2,585
Total Plan assets	$	1,366,043	$	52,168	$	1,418,211	$	1,186,433	$	52,286	$	1,238,719

▪Global equities, including domestic equities

▪International developed countries equities

▪Domestic equities

▪Emerging markets equities

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Summary of Income Before Taxes and Noncontrolling Interest for Domestic and Foreign Operations

The following is a summary of income before taxes and noncontrolling interests for domestic and foreign operations:


	Year ended December 31,
(Thousands of dollars)	2021		2020		2019
U.S.	$	221,507	$	282,489	$	261,525
Foreign	25,343		22,249		11,145
Total income before income taxes	$	246,850	$	304,738	$	272,670

Summary of Income Tax Expense (Benefit)

Income tax expense (benefit) consists of the following:


	Year Ended December 31,
(Thousands of dollars)	2021		2020		2019
Current:
Federal	$	(2,872)	$	6,287	$	622
State	(11,516)		8,617		(1,510)
Foreign	6,524		4,666		5,013
	(7,864)		19,570		4,125
Deferred:
Federal	39,117		44,547		45,593
State	8,239		414		8,212
Foreign	156		1,222		(1,907)
	47,512		46,183		51,898
Total income tax expense	$	39,648	$	65,753	$	56,023

Income tax expense (benefit) consists of the following:


	Year Ended December 31,
(Thousands of dollars)	2021		2020		2019
Current:
Federal	$	(3,643)	$	(4,678)	$	4,109
State	(6,556)		(179)		250
	(10,199)		(4,857)		4,359
Deferred:
Federal	36,842		38,561		29,543
State	2,695		2,051		1,071
	39,537		40,612		30,614
Total income tax expense	$	29,338	$	35,755	$	34,973

Significant Components of Deferred Income Tax Expense (Benefit)

Deferred income tax expense (benefit) consists of the following significant components:


	Year Ended December 31,
(Thousands of dollars)	2021		2020		2019
Deferred federal and state:
Property-related items	$	35,072	$	50,504	$	60,449
Purchased gas cost adjustments	73,613		(5,726)		3,834
Employee benefits	(1,484)		459		7,680
Regulatory adjustments	(10,101)		(9,885)		(11,962)
Deferred payroll taxes	(6,344)		(9,055)		—
Deferred revenue	6,021		588		822
Net operating loss	(65,509)		3,349		5,658
Alternative minimum tax	—		4,409		441
All other deferred	16,296		11,592		(14,778)
Total deferred federal and state	47,564		46,235		52,144
Deferred ITC, net	(52)		(52)		(246)
Total deferred income tax expense	$	47,512	$	46,183	$	51,898

Deferred income tax expense (benefit) consists of the following significant components:


	Year Ended December 31,
(Thousands of dollars)	2021		2020		2019
Deferred federal and state:
Property-related items	$	23,077	$	36,029	$	34,398
Purchased gas cost adjustments	73,613		(5,726)		3,834
Employee benefits	5,508		11,437		6,493
Regulatory adjustments	(10,101)		(9,885)		(11,962)
Deferred payroll taxes	(892)		(1,810)		—
Alternative minimum tax	—		4,409		441
Net operating loss	(59,119)		—		—
All other deferred	7,503		6,210		(2,344)
Total deferred federal and state	39,589		40,664		30,860
Deferred ITC, net	(52)		(52)		(246)
Total deferred income tax expense	$	39,537	$	40,612	$	30,614

Reconciliation of U.S Federal Statutory Rate to Consolidated Effective Tax Rate

A reconciliation of the U.S. federal statutory rate to the consolidated effective tax rate (and the sources of these differences and the effect of each) are summarized as follows:


	Year Ended December 31,
	2021		2020		2019
U.S. federal statutory income tax rate	21.0	%	21.0	%	21.0	%
Net state taxes	1.0		3.0		2.1
Tax credits	(0.5)		(0.5)		(0.3)
Company-owned life insurance	(1.1)		(0.8)		(1.5)

Amortization of excess deferred taxes	(4.3)		(0.8)		(0.9)
All other differences	—		(0.3)		0.1
Consolidated effective income tax rate	16.1	%	21.6	%	20.5	%

A reconciliation of the U.S. federal statutory rate to the consolidated effective tax rate (and the sources of these differences and the effect of each) are summarized as follows:


	Year Ended December 31,
	2021		2020		2019
U.S. federal statutory income tax rate	21.0	%	21.0	%	21.0	%
Net state taxes	0.3		1.7		0.7
Tax credits	(0.6)		(0.7)		(0.4)
Company-owned life insurance	(0.9)		(1.0)		(1.9)

Amortization of excess deferred taxes	(4.9)		(1.3)		(1.2)
All other differences	(1.3)		(1.4)		(0.5)
Effective income tax rate	13.6	%	18.3	%	17.7	%

Deferred Tax Assets and Liabilities

Deferred tax assets and liabilities consist of the following:


	December 31,
(Thousands of dollars)	2021		2020
Deferred tax assets:
Deferred income taxes for future amortization of ITC and excess deferred taxes	$	116,496	$	104,314
Employee benefits	39,181		39,907

Federal net operating losses	94,383		4,118
Deferred payroll taxes	6,344		9,055
Lease-related item	18,462		20,890
Other	15,739		14,350
Valuation allowance	(22)		(22)
	290,583		192,612
Deferred tax liabilities:
Property-related items, including accelerated depreciation	843,559		785,734
Regulatory balancing accounts	77,818		4,205

Debt-related costs	2,277		2,585
Intangibles	97,860		13,511
Lease-related item	17,254		19,789
Other	20,562		13,786
	1,059,330		839,610
Net noncurrent deferred tax liabilities	$	768,747	$	646,998

Deferred tax assets and liabilities consist of the following:


	December 31,
(Thousands of dollars)	2021		2020
Deferred tax assets:
Deferred income taxes for future amortization of ITC and excess deferred taxes	$	101,133	$	104,314
Employee benefits	(4,671)		4,806
Federal net operating losses	59,119		—
Deferred payroll taxes	892		1,810
Other	6,777		7,790
Valuation allowance	(22)		(22)
	163,228		118,698
Deferred tax liabilities:
Property-related items, including accelerated depreciation	703,374		680,294
Regulatory balancing accounts	77,818		4,205

Debt-related costs	2,277		2,585
Other	18,587		12,714
	802,056		699,798
Net deferred tax liabilities	$	638,828	$	581,100

Reconciliation of Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:


	December 31,
(Thousands of dollars)	2021		2020
Unrecognized tax benefits at beginning of year	$	1,928	$	1,056
Gross increases – tax positions in prior period	442		641
Gross decreases – tax positions in prior period	—		—
Gross increases – current period tax positions	259		231
Gross decreases – current period tax positions	—		—
Settlements	—		—
Lapse in statute of limitations	—		—
Unrecognized tax benefits at end of year	$	2,629	$	1,928

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:


	December 31,
(Thousands of dollars)	2021		2020
Unrecognized tax benefits at beginning of year	$	1,793	$	1,056
Gross increases – tax positions in prior period	310		506
Gross decreases – tax positions in prior period	—		—
Gross increases – current period tax positions	259		231
Gross decreases – current period tax positions	—		—
Settlements	—		—
Lapse in statute of limitations	—		—
Unrecognized tax benefits at end of year	$	2,362	$	1,793

Summary of Income Before Taxes for Continuing and Discontinued Operations

The following is a summary of income before taxes:


	Year ended December 31,
(Thousands of dollars)	2021		2020		2019
Total income before income taxes	$	216,473	$	194,873	$	198,144

Segment Information (Tables)

12 Months Ended

Dec. 31, 2021

Segment Reporting [Abstract]

Schedule of Accounts Receivable for Services

Accounts receivable for these services, which are not eliminated during consolidation, are presented in the table below:


	December 31,
(Thousands of dollars)	2021		2020
Accounts receivable for Centuri services	$	15,166	$	13,956

Schedule of Revenues by Geographic Area

The following table presents the amount of revenues for both the natural gas distribution and utility infrastructure services segments (legacy segments) by geographic area:


	December 31,
(Thousands of dollars)	2021		2020		2019
Revenues (a)
United States	$	3,411,018	$	3,057,041	$	2,893,201
Canada	269,433		241,832		226,716
Total	$	3,680,451	$	3,298,873	$	3,119,917

(a)Revenues are attributed to countries based on the location of customers.

Schedule of Segment Reporting Information

The financial information pertaining to each segment as of and for the three years ended December 31, 2021, 2020, and 2019 are as follows:


	Year Ended December 31, 2021
(Thousands of dollars)	Natural Gas Distribution		Utility Infrastructure Services		Pipeline and Storage		Other		Total
Revenues from external customers	$	1,521,790	$	2,056,315	$	—	$	—	$	3,578,105
Intersegment sales	—		102,346		—		—		102,346
Total	$	1,521,790	$	2,158,661	$	—	$	—	$	3,680,451
Interest income	$	5,113	$	—	$	—	$	—	$	5,113
Interest expense	$	97,560	$	20,999	$	—	$	639	$	119,198
Depreciation and amortization	$	253,398	$	117,643	$	—	$	—	$	371,041
Income tax expense	$	29,338	$	18,776	$	—	$	(8,466)	$	39,648
Segment net income	$	187,135	$	40,420	$	—	$	(26,776)	$	200,779
Segment assets	$	7,950,263	$	2,579,748	$	2,187,582	$	47,664	$	12,765,257
Capital expenditures	$	601,983	$	113,643	$	—	$	—	$	715,626


	Year Ended December 31, 2020
(Thousands of dollars)	Natural Gas Distribution		Utility Infrastructure Services		Other		Total
Revenues from external customers	$	1,350,585	$	1,813,429	$	—	$	3,164,014
Intersegment sales	—		134,859		—		134,859
Total	$	1,350,585	$	1,948,288	$	—	$	3,298,873
Interest income	$	4,015	$	—	$	—	$	4,015
Interest expense	$	101,148	$	9,269	$	1,060	$	111,477
Depreciation and amortization	$	235,295	$	96,732	$	—	$	332,027
Income tax expense	$	35,755	$	31,128	$	(1,130)	$	65,753
Segment net income	$	159,118	$	74,862	$	(1,656)	$	232,324
Segment assets	$	7,256,636	$	1,475,237	$	3,980	$	8,735,853
Capital expenditures	$	692,216	$	132,889	$	—	$	825,105


	Year Ended December 31, 2019
(Thousands of dollars)	Natural Gas Distribution		Utility Infrastructure Services		Other		Total
Revenues from external customers	$	1,368,939	$	1,592,252	$	—	$	2,961,191
Intersegment sales	—		158,726		—		158,726
Total	$	1,368,939	$	1,750,978	$	—	$	3,119,917
Interest income	$	6,356	$	—	$	—	$	6,356
Interest expense	$	95,026	$	14,086	$	114	$	109,226
Depreciation and amortization	$	215,620	$	87,617	$	—	$	303,237
Income tax expense	$	34,973	$	21,399	$	(349)	$	56,023
Segment net income	$	163,171	$	52,404	$	(1,639)	$	213,936
Segment assets	$	6,798,746	$	1,365,194	$	6,108	$	8,170,048
Capital expenditures	$	778,748	$	159,400	$	—	$	938,148

Redeemable Noncontrolling Interests (Tables)

12 Months Ended

Dec. 31, 2021

Noncontrolling Interest [Abstract]

Summary of Redeemable Noncontrolling Interest

The following depicts changes to the balances of the redeemable noncontrolling interests:


	Linetec		Drum		Total
(Thousands of dollars)
Balance, December 31, 2019	$	84,542	$	—	$	84,542
Net income attributable to redeemable noncontrolling interests	6,661		—		6,661
Redemption value adjustment	74,513		—		74,513
Balance, December 31, 2020	165,716		—		165,716
Redeemable noncontrolling interest acquired	—		12,562		12,562
Net income attributable to redeemable noncontrolling interests	6,416		7		6,423
Redemption value adjustment	12,016		—		12,016
Balance, December 31, 2021	$	184,148	$	12,569	$	196,717

Business Acquisitions (Tables)

12 Months Ended

Dec. 31, 2021

Business Combination and Asset Acquisition [Abstract]

Summary of Fair Values of Assets Acquired and Liabilities Assumed

The preliminary estimated fair values of assets acquired and liabilities assumed as of August 27, 2021, are as follows:


(Millions of dollars)	Acquisition Date		Measurement Period Adjustments		Revised Acquisition Date
Cash and cash equivalents	$	1.9	$	—	$	1.9
Accounts receivable	69.1		(8.6)		60.5
Contract assets	40.1		7.4		47.5
Income taxes receivable, net	0.7		—		0.7
Right of use assets under operating leases	1.5		—		1.5
Prepaid expenses	5.2		—		5.2
Property and equipment	118.1		1.2		119.3
Intangible assets	335.0		(31.5)		303.5
Goodwill	446.8		2.7		449.5
Total assets acquired	1,018.4		(28.8)		989.6

Trade and other payables	46.2		—		46.2
Finance lease obligations	27.5		1.2		28.7
Contract liabilities	12.7		—		12.7
Operating lease obligations	1.5		—		1.5
Other liabilities	5.3		(0.3)		5.0
Deferred tax liabilities	94.8		(23.4)		71.4
Total liabilities assumed and noncontrolling interest	188.0		(22.5)		165.5
Net assets acquired	$	830.4	$	(6.3)	$	824.1

The preliminary estimated fair values of assets acquired and liabilities assumed as of December 31, 2021, are as follows (in millions of dollars):


Gas plant, net	$	1,047.4
Other property and investments	51.3
Cash and cash equivalents	17.6
Accounts receivable, net of allowances	26.6
Prepaid and other current assets	27.4
Deferred charges and other assets	31.1
Goodwill	986.2
Deferred income taxes	15.4
Total assets acquired	2,203.0

Long-term debt	449.7
Accounts payable	7.0
Deferred purchased gas costs	5.7
Customer deposits	3.2
Accrued general taxes	0.4
Accrued interest	4.7
Other current liabilities	14.5
Accumulated removal costs	56.6
Other deferred credits	85.6
Total liabilities assumed	627.4
Net assets acquired	$	1,575.6

Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination

The amounts allocated to major classes of intangibles are as follows:


(Thousands of dollars)	Estimated Fair Value		Estimated Weighted Average Useful Life in Years
Backlog	$	4,500	1
Trade name	60,000		15
Customer relationships	239,000		19
	$	303,500

Business Acquisition, Pro Forma Information


(Thousands of dollars)	December 31, 2021
Utility infrastructure services revenues	$	163,830
Net income attributable to Southwest Gas Holdings, Inc.	$	1,374

Amounts below are in millions of dollars, except per share amounts.


	Unaudited
	Year Ended December 31,
	2021		2020
Total operating revenues	$	4,236	$	3,980
Net income attributable to Southwest Gas Holdings, Inc.	$	278	$	276
Basic earnings per share	$	4.70	$	4.93
Diluted earnings per share	$	4.69	$	4.93

Background, Organization, and Summary of Significant Accounting Policies - Narrative (Details)			1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 01, 2022	Dec. 31, 2021 USD ($)	Nov. 30, 2021 USD ($)	Sep. 30, 2021 USD ($) instrument	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2021 USD ($)	Nov. 30, 2018
Significant Accounting Policies [Line Items]
Amortization expenses					$ 17,300,000	$ 10,800,000	$ 10,700,000
Capital Expenditures Incurred but Not yet Paid					19,400,000
Cumulative foreign earnings		$ 59,000,000			$ 59,000,000
Deferred purchased gas costs, recovered or refunded period					1 year
Accrued purchased gas costs		52,000,000			$ 52,000,000	29,000,000
Gas pipe materials and operating supplies		62,900,000			62,900,000	50,000,000
Gas pipe materials and operating supplies, including portion from acquisition		67,400,000			67,400,000
Reclassification amount from Net utility plant to Prepaid and other current assets				$ 31,000,000
Goodwill impairment charges					0	0
Subsequent Event \| Minimum
Significant Accounting Policies [Line Items]
Entity separation, completion period	9 months
Subsequent Event \| Maximum
Significant Accounting Policies [Line Items]
Entity separation, completion period	12 months
Interest Rate Swap
Significant Accounting Policies [Line Items]
Derivative, number of instruments held \| instrument				2
Linetec
Significant Accounting Policies [Line Items]
Ownership percentage by noncontrolling owners									20.00%
Drum
Significant Accounting Policies [Line Items]
Ownership percentage by noncontrolling owners			1.42%
$250 Million Term Loan
Significant Accounting Policies [Line Items]
Debt instrument face amount								$ 250,000,000
Money Market Funds
Significant Accounting Policies [Line Items]
Cash and cash equivalents		20,000,000			$ 20,000,000	$ 0
W.S. Nicholls Western Construction LTD
Significant Accounting Policies [Line Items]
VIE ownership percentage					50.00%
Maximum loss exposure amount		12,600,000			$ 12,600,000
White River Hub, LLC
Significant Accounting Policies [Line Items]
VIE ownership percentage					50.00%
Maximum loss exposure amount		25,600,000			$ 25,600,000
Questar Pipelines
Significant Accounting Policies [Line Items]
Debt instrument face amount		430,000,000			430,000,000
Gas pipe materials and operating supplies		4,500,000			$ 4,500,000
Business combination consideration		$ 1,576,000,000
Questar Pipelines \| Term Loan Facility due December 30, 2022 \| Loans Payable
Significant Accounting Policies [Line Items]
Debt instrument face amount			$ 1,600,000,000
Debt Instrument, term			364 days

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Other Property and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Net cash surrender value of COLI policies	$ 149,947	$ 140,874
Other property	59,337	23,961
Non-regulated property, equipment, and intangibles	1,616,392	1,089,414
Non-regulated accumulated provision for depreciation and amortization	(512,343)	(422,741)
Total	$ 153,093	$ 143,611

Background, Organization, and Summary of Significant Accounting Policies - Summary of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 477,984	$ 180,576
Accumulated Amortization	(51,479)	(40,392)
Net Carrying Amount	426,505	140,184
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	393,834	154,757
Accumulated Amortization	(42,886)	(29,237)
Net Carrying Amount	350,948	125,520
Trade name and trademarks
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	79,650	23,618
Accumulated Amortization	(7,093)	(8,954)
Net Carrying Amount	72,557	14,664
Customer contracts backlog
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,500	270
Accumulated Amortization	(1,500)	(270)
Net Carrying Amount	$ 3,000	0
Noncompete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount		1,931
Accumulated Amortization		(1,931)
Net Carrying Amount		$ 0

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Estimated Future Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
2022	$ 29,814
2023	26,814
2024	26,814
2025	26,769
2026	26,580
Thereafter	289,714
Net Carrying Amount	$ 426,505	$ 140,184

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 10,095	$ 343,023
Foreign currency translation adjustment	468	2,161
Goodwill, ending balance	10,095	10,095
Riggs Distler
Goodwill [Roll Forward]
Goodwill from acquisition	449,501
Questar Pipelines
Goodwill [Roll Forward]
Goodwill from acquisition	986,179
Goodwill, ending balance	986,200
Natural Gas Distribution
Goodwill [Roll Forward]
Goodwill, beginning balance	10,095	10,095
Foreign currency translation adjustment	0	0
Goodwill, ending balance	10,095	10,095
Natural Gas Distribution \| Riggs Distler
Goodwill [Roll Forward]
Goodwill from acquisition	0
Natural Gas Distribution \| Questar Pipelines
Goodwill [Roll Forward]
Goodwill from acquisition	0
Utility Infrastructure Services
Goodwill [Roll Forward]
Goodwill, beginning balance	335,089	332,928
Foreign currency translation adjustment	468	2,161
Goodwill, ending balance	785,058	335,089
Utility Infrastructure Services \| Riggs Distler
Goodwill [Roll Forward]
Goodwill from acquisition	449,501
Utility Infrastructure Services \| Questar Pipelines
Goodwill [Roll Forward]
Goodwill from acquisition	0
Pipeline and Storage
Goodwill [Roll Forward]
Goodwill, beginning balance	0	0
Foreign currency translation adjustment	0	0
Goodwill, ending balance	986,179	$ 0
Pipeline and Storage \| Riggs Distler
Goodwill [Roll Forward]
Goodwill from acquisition	0
Pipeline and Storage \| Questar Pipelines
Goodwill [Roll Forward]
Goodwill from acquisition	$ 986,179

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Capitalized and Debt Portion of AFUDC (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Debt portion	$ 1,046	$ 3,202	$ 4,558
Equity portion	0	4,724	4,161
AFUDC capitalized as part of regulated operations plant	$ 1,046	$ 7,926	$ 8,719
AFUDC rate	0.96%	5.51%	5.36%

Background, Organization, and Summary of Significant Accounting Policies - Other Income (Deductions) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other income (deductions)
Interest income	$ 5,113	$ 4,015	$ 6,356
Equity AFUDC	0	4,724	4,161
Total other income (deductions)	(4,559)	(6,590)	9,517
Corporate and administrative
Other income (deductions)
Total other income (deductions)	(7)	8	102
Natural Gas Distribution
Other income (deductions)
Interest income	5,113	4,015	6,356
Natural Gas Distribution \| Operating Segments
Other income (deductions)
Change in COLI policies	8,800	9,200	17,400
Interest income	5,113	4,015	6,356
Equity AFUDC	0	4,724	4,161
Other components of net periodic benefit cost	(14,021)	(20,022)	(15,059)
Miscellaneous income and (expense)	(4,451)	(4,507)	(3,341)
Total other income (deductions)	(4,559)	(6,590)	9,517
Utility Infrastructure Services
Other income (deductions)
Interest income	0	0	0
Utility Infrastructure Services \| Operating Segments
Other income (deductions)
Miscellaneous income and (expense)	863	(271)	(519)
Foreign transaction gain (loss)	(22)	(16)	546
Equity in earnings of unconsolidated investment – Western	226	80	439
Total other income (deductions)	$ 1,067	$ (207)	$ 466

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Earnings Per Share, Basic and Diluted (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Weighted average basic shares (in shares)	59,145,000	55,998,000	54,245,000
Effect of dilutive securities:
Management Incentive Plan shares (in shares)	0	0	12,000
Restricted stock units (in shares)	114,000	78,000	55,000
Average diluted shares (in shares)	59,259,000	56,076,000	54,312,000
Number of performance share units granted (in shares)	104,000	69,000	46,000

Regulated Operations Plant and Leases - Schedule of Regulated Operations Plant (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Public Utility, Property, Plant and Equipment [Line Items]
Gas plant	$ 8,901,575	$ 8,384,000
Less: accumulated depreciation	(2,538,508)	(2,419,348)
Construction work in progress	183,485	211,429
Net regulated operations plant	6,546,552	6,176,081
Storage
Public Utility, Property, Plant and Equipment [Line Items]
Gas plant	103,874	101,203
Transmission
Public Utility, Property, Plant and Equipment [Line Items]
Gas plant	397,590	400,657
Distribution
Public Utility, Property, Plant and Equipment [Line Items]
Gas plant	7,506,489	7,078,656
General
Public Utility, Property, Plant and Equipment [Line Items]
Gas plant	496,643	515,879
Software and software-related intangibles
Public Utility, Property, Plant and Equipment [Line Items]
Gas plant	380,372	270,883
Other
Public Utility, Property, Plant and Equipment [Line Items]
Gas plant	$ 16,607	$ 16,722

Regulated Operations Plant and Leases - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Annual utility depreciation and amortization expense percentage	2.70%	2.70%	2.70%
Amortization of intangibles	$ 17.3	$ 10.8	$ 10.7
Lease remaining lease term (up to)	17 years
Lease renewal term (up to)	5 years
Lease termination period	1 year
Short-term lease, terms less than one month, cost		66.4	67.0
Short-term lease total future lease payments	$ 1.7
Gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Amortization of intangibles	$ 17.7	$ 13.7	$ 13.2
Gas, Transmission and Distribution Plant
Public Utility, Property, Plant and Equipment [Line Items]
Annual utility depreciation and amortization expense percentage			2.30%

Regulated Operations Plant and Leases - Schedule of Depreciation and Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 253,398	$ 235,295	$ 215,620
Gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 230,245	$ 215,636	$ 197,358

Regulated Operations Plant and Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 15,279	$ 14,294	$ 12,235
Amortization of ROU assets	2,138	140	137
Interest on lease liabilities	278	37	34
Total finance lease cost	2,416	177	171
Short-term lease cost	103,800	19,806	16,217
Total lease cost - Southwest Gas Holdings, Inc.	$ 122,516	$ 35,528	$ 30,154

Regulated Operations Plant and Leases - Supplemental Cash Flow Information Related to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating cash flows from operating leases	$ 15,413	$ 13,655	$ 12,444
Operating cash flows from finance leases	278	36	33
Financing cash flows from finance leases	3,547	199	212
Operating leases	12,206	20,919	24,687
Finance leases	$ 3,332	$ 361	$ 13,839

Regulated Operations Plant and Leases - Supplemental Information Related to Leases Included in Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Operating lease ROU assets	$ 80,638	$ 81,010
Operating lease liabilities, current	12,185	10,032
Operating lease liabilities, noncurrent	72,930	75,247
Total	$ 85,115	$ 85,279
Operating lease, weighted average remaining lease term (in years)	7 years 6 months 25 days	10 years 29 days
Finance lease, weighted average remaining lease term (in years)	3 years 11 months 1 day	2 years 1 month 13 days
Operating lease, weighted average discount rate	3.95%	4.05%
Finance lease, weighted average discount rate	2.58%	5.55%
Finance lease ROU assets	$ 30,705	$ 752
Finance lease liabilities, current	8,858	202
Finance lease liabilities, noncurrent	20,585	490
Finance lease liabilities	$ 29,443	$ 692

Regulated Operations Plant and Leases - Schedule of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Operating Leases
2022	$ 15,200
2023	13,402
2024	11,321
2025	9,228
2026	7,878
Thereafter	45,529
Total lease payments	102,558
Less imputed interest	17,443
Operating lease liabilities	85,115	$ 85,279
Finance Leases
2022	9,494
2023	7,940
2024	6,476
2025	3,987
2026	2,108
Thereafter	1,008
Total lease payments	31,013
Less imputed interest	1,570
Finance lease liabilities	$ 29,443	$ 692

Revenue - Narrative (Details) $ in Thousands	12 Months Ended
Revenue - Narrative (Details) $ in Thousands	Dec. 31, 2021 USD ($) type customer contract	Aug. 27, 2021 USD ($)	Dec. 31, 2020 USD ($) customer
Segment Reporting Information [Line Items]
Number of types of services provided to customers \| type	3
Number of customers \| customer	2,200,000
Number of types of agreements with customers \| type	2
Change in contract liability, revenue recognized	$ 4,500
Number of contracts with original duration more than one year \| contract	26
Amounts billed in excess of revenue earned on contracts	$ 11,860		$ 4,507
Number of customers party to contracts with rate components subject to negotiation (less than) \| customer			24
Drum
Segment Reporting Information [Line Items]
Contract assets	47,500	$ 40,100
Contract liabilities	12,700	$ 12,700
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Segment Reporting Information [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 105,300
Revenue, expected to be recognized on multi-year contracts, period	2 years

Revenue - Schedule of Gas Operating Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 2,158,661	$ 1,948,288	$ 1,750,978
Alternative revenue program deferrals	13,181	12,140	(25,112)
Other revenues	10,859	(706)	8,757
Total Gas operating revenues	1,521,790	1,350,585	1,368,939
Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,035,612	958,520	972,788
Small commercial
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	270,214	221,541	249,117
Large commercial
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	57,371	44,633	48,935
Industrial/other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	42,313	26,242	22,074
Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 92,240	$ 88,215	$ 92,380

Revenue - Summary of Revenue Disaggregated by Service Type, and Contract Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 2,158,661	$ 1,948,288	$ 1,750,978
Master services agreement
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,652,978	1,490,009	1,383,377
Bid contract
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	505,683	458,279	367,601
Unit price contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,369,082	1,356,640	1,380,256
Fixed price contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	267,742	157,701	112,924
Time and materials contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	521,837	433,947	257,798
Gas infrastructure services
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,302,340	1,261,160	1,238,974
Electric power infrastructure services
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	525,202	411,826	247,717
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 331,119	$ 275,302	$ 264,287

Revenue - Summary of Information about Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contracts receivable, net	$ 296,005	$ 278,316
Revenue earned on contracts in progress in excess of billings	214,774	96,996
Amounts billed in excess of revenue earned on contracts	$ 11,860	$ 4,507

Revenue - Schedule of Utility Infrastructure Services Contracts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Contracts receivable, gross	$ 296,262	$ 280,470
Allowance for doubtful accounts	(257)	(2,154)
Contracts receivable, net	296,005	278,316
Billed on completed contracts and contracts in progress
Disaggregation of Revenue [Line Items]
Contracts receivable, gross	292,770	273,778
Other receivables
Disaggregation of Revenue [Line Items]
Contracts receivable, gross	$ 3,492	$ 6,692

Revenue - Operating Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Operating revenue from contracts with customers	$ 2,158,661	$ 1,948,288	$ 1,750,978
Other revenue	$ 10,859	$ (706)	$ 8,757

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9031-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130543-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9054-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

Revenue - Revenue Performance Obligation (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 $ in Millions	Dec. 31, 2021 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 105.3
Revenue, expected to be recognized on multi-year contracts, period	2 years

Receivables and Related Allowances - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) state	Dec. 31, 2020 USD ($)
Receivables And Related Allowances [Line Items]
Number of states in which entity operates \| state	3
Accounts receivable, extending period	1 month
Threshold period after inactivation for write-off of accounts receivable	60 days
Customer accounts receivable \| $	$ 510,800	$ 146,861

Receivables and Related Allowances - Schedule of Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Receivables [Abstract]
Gas utility customer accounts receivable balance	$ 169,114	$ 145,108

Receivables and Related Allowances - Schedule of Percent of Customers by State (Details)	12 Months Ended
	Dec. 31, 2021
Arizona
Receivables And Related Allowances [Line Items]
Percent of customers by state:	53.00%
Nevada
Receivables And Related Allowances [Line Items]
Percent of customers by state:	37.00%
California
Receivables And Related Allowances [Line Items]
Percent of customers by state:	10.00%

Receivables and Related Allowances - Schedule of Allowance for Uncollectibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 4,334	$ 2,095	$ 2,168
Additions charged to expense	5,415	4,693	3,507
Accounts written off, less recoveries	(6,490)	(2,454)	(3,580)
Ending Balance	$ 3,259	$ 4,334	$ 2,095

Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	$ 798,897	$ 541,647
Net regulatory liabilities	$ (95,640)	(406,291)
Accrued pension and other postretirement benefit costs, recovery period	5 years
Other deferred credits and other long-term liabilities	$ 881,286	1,043,337
Regulatory assets, accrued absence time, lag period	1 year
Regulatory assets, margin, interest and property tax-tracking, recovery period	24 months
MountainWest unsecured senior notes, 4.875%, due in 2041 \| Questar Pipelines
Regulatory Assets And Liabilities [Line Items]
Proceeds from debt	$ 180,000
Debt instrument, stated interest rate	4.875%
Other current liabilities
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	$ (29,000)
Other deferred credits and other long-term liabilities	2,000
Deferred purchased gas costs
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	0	(54,636)
Accumulated removal costs
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	(424,000)	(404,000)
Unamortized gain on reacquired debt
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	(7,108)	(7,644)
Regulatory excess deferred/other taxes and gross-up
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	(446,333)	(461,023)
Margin, interest - and property tax-tracking
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	(8,523)	(17,132)
Unrecognized other postretirement benefit cost
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	0	0
Other regulatory liabilities
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	(8,573)	(3,503)
Gross-up related to contributions in aid of construction
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	(2,600)
Accrued pension and other postretirement benefit costs
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	339,356	427,550
Deferred purchased gas costs
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	291,145	2,053
Settled interest rate hedges
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	0	0
Accrued purchased gas costs
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	51,631	29,000
Unamortized premium on reacquired debt
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	16,283	17,124
Accrued absence time
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	16,975	15,565
Margin, interest - and property tax-tracking
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	22,709	4,759
Other
Regulatory Assets And Liabilities [Line Items]
Regulatory assets	$ 60,798	$ 45,596

Regulatory Assets and Liabilities - Schedule of Components of Other Regulatory Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Regulatory assets	$ 798,897	$ 541,647
State mandated public purpose programs (including low income and conservation programs)
Regulatory Assets [Line Items]
Regulatory assets	15,239	11,527
Infrastructure replacement programs and similar
Regulatory Assets [Line Items]
Regulatory assets	6,545	7,731
Environmental compliance programs
Regulatory Assets [Line Items]
Regulatory assets	6,807	5,235
Pension tracking mechanism
Regulatory Assets [Line Items]
Regulatory assets	10,281	3,075
Other
Regulatory Assets [Line Items]
Regulatory assets	21,926	18,028
Other
Regulatory Assets [Line Items]
Regulatory assets	60,798	45,596
Prepaids and other current assets \| Environmental compliance programs
Regulatory Assets [Line Items]
Regulatory assets	5,800	4,200
Prepaids and other current assets \| Other
Regulatory Assets [Line Items]
Regulatory assets	7,700	3,600
Deferred charges and other assets \| Environmental compliance programs
Regulatory Assets [Line Items]
Regulatory assets	1,000	998
Deferred charges and other assets \| Other
Regulatory Assets [Line Items]
Regulatory assets	$ 15,600	$ 14,400

Regulatory Assets and Liabilities - Schedule of Components of Other Regulatory Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Other deferred credits and other long-term liabilities
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ (13)
State mandated public purpose programs (including low income and conservation programs)
Regulatory Liabilities [Line Items]
Regulatory liabilities	(1,886)	$ (834)
Environmental compliance programs
Regulatory Liabilities [Line Items]
Regulatory liabilities	(4,182)	(405)
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities	(2,505)	(2,264)
Other regulatory liabilities
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ (8,573)	$ (3,503)

Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - Related Tax Effects Allocated to OCI (Detail) - USD ($) $ in Thousands	12 Months Ended			36 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, net of tax	$ 44,974
Other comprehensive income (loss), before tax	18,732	$ (6,159)	$ (5,992)
Other comprehensive income (loss), tax	(4,490)	1,888	1,928
Total other comprehensive income (loss), net of tax	$ 14,222	$ (5,984)	$ (6,102)
Effective income tax rate	13.60%	18.30%	17.70%	24.00%
Net actuarial gain/(loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax	$ 59,176	$ (57,539)	$ (71,087)
Other comprehensive income (loss) before reclassifications, tax	(14,202)	13,809	17,061
Other comprehensive income (loss) before reclassifications, net of tax	44,974	(43,730)	(54,026)
Reclassification from AOCI, before Tax	44,597	37,830	23,376
Reclassification from AOCI, tax	(10,703)	(9,079)	(5,610)
Reclassification from AOCI, net of tax	33,894	28,751	17,766
Other comprehensive income (loss), before tax	44,597
Other comprehensive income (loss), tax	(10,703)
Total other comprehensive income (loss), net of tax	33,894
Amortization of prior service cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	959	1,155	1,271
Reclassification from AOCI, tax	(230)	(277)	(305)
Reclassification from AOCI, net of tax	729	878	966
Other comprehensive income (loss), before tax	959
Other comprehensive income (loss), tax	(230)
Total other comprehensive income (loss), net of tax	729
Prior service cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax	0	0	(1,878)
Other comprehensive income (loss) before reclassifications, tax	0	0	452
Other comprehensive income (loss) before reclassifications, net of tax	0	0	(1,426)
Regulatory adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	(88,194)	7,435	36,944
Reclassification from AOCI, tax	21,167	(1,785)	(8,867)
Reclassification from AOCI, net of tax	(67,027)	5,650	28,077
Other comprehensive income (loss), before tax	(88,194)
Other comprehensive income (loss), tax	21,167
Total other comprehensive income (loss), net of tax	(67,027)
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax	59,176
Other comprehensive income (loss) before reclassifications, tax	(14,202)
Other comprehensive income (loss) before reclassifications, net of tax	44,974
Other comprehensive income (loss), before tax	16,538	(11,119)	(11,374)
Other comprehensive income (loss), tax	(3,968)	2,668	2,731
Total other comprehensive income (loss), net of tax	12,570	(8,451)	(8,643)
FSIRS
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	2,174	3,247	3,344
Reclassification from AOCI, tax	(522)	(780)	(803)
Reclassification from AOCI, net of tax	1,652	2,467	2,541
Other comprehensive income (loss), before tax	2,174	3,247	3,344
Other comprehensive income (loss), tax	(522)	(780)	(803)
Total other comprehensive income (loss), net of tax	1,652	2,467	2,541
Foreign currency items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax	20	1,713	2,038
Other comprehensive income (loss) before reclassifications, tax	0	0	0
Other comprehensive income (loss) before reclassifications, net of tax	$ 20	$ 1,713	$ 2,038

Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - Narrative (Detail) $ in Thousands	Dec. 31, 2021 USD ($)
Equity [Abstract]
Amount of FSIRS existing AOCI losses expected to be reclassified into interest expense	$ 416

Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - AOCI Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended			36 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 2,233,468	$ 2,005,152
Beginning balance, attributable to parent	2,233,468
Other comprehensive income (loss) before reclassifications, net of tax	44,974
Other comprehensive income (loss), before tax	18,732	(6,159)	$ (5,992)
Other comprehensive income (loss), tax	(4,490)	1,888	1,928
Total other comprehensive income (loss), net of tax	14,222	(5,984)	(6,102)
Ending balance, attributable to parent	2,527,937	2,233,468		$ 2,233,468
Ending balance	$ 2,527,937	$ 2,233,468	$ 2,005,152	$ 2,233,468
Effective income tax rate	13.60%	18.30%	17.70%	24.00%
Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, before tax	$ (77,720)
Beginning balance, tax	18,653
Beginning balance	(59,067)
Beginning balance, attributable to parent, before tax	(77,720)
Beginning balance, attributable to parent, tax	18,653
Beginning balance, attributable to parent	(59,067)
Other comprehensive income (loss) before reclassifications, before tax	59,176
Other comprehensive income (loss) before reclassifications, tax	(14,202)
Other comprehensive income (loss) before reclassifications, net of tax	44,974
Other comprehensive income (loss), before tax	16,538	$ (11,119)	$ (11,374)
Other comprehensive income (loss), tax	(3,968)	2,668	2,731
Total other comprehensive income (loss), net of tax	12,570	(8,451)	(8,643)
Ending balance, attributable to parent, before tax	(61,182)	(77,720)		$ (77,720)
Ending balance, attributable to parent, tax	14,685	18,653		18,653
Ending balance, attributable to parent	(46,497)	(59,067)		(59,067)
Ending balance, before tax	(61,182)	(77,720)		(77,720)
Ending balance, tax	14,685	18,653		18,653
Ending balance	(46,497)	(59,067)		(59,067)
Amortization of prior service cost
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, before Tax	959	1,155	1,271
Reclassification from AOCI, tax	(230)	(277)	(305)
Reclassification from AOCI, net of tax	729	878	966
Other comprehensive income (loss), before tax	959
Other comprehensive income (loss), tax	(230)
Total other comprehensive income (loss), net of tax	729
Amortization of net actuarial loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications, before tax	59,176	(57,539)	(71,087)
Other comprehensive income (loss) before reclassifications, tax	(14,202)	13,809	17,061
Other comprehensive income (loss) before reclassifications, net of tax	44,974	(43,730)	(54,026)
Reclassification from AOCI, before Tax	44,597	37,830	23,376
Reclassification from AOCI, tax	(10,703)	(9,079)	(5,610)
Reclassification from AOCI, net of tax	33,894	28,751	17,766
Other comprehensive income (loss), before tax	44,597
Other comprehensive income (loss), tax	(10,703)
Total other comprehensive income (loss), net of tax	33,894
Regulatory adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, before Tax	(88,194)	7,435	36,944
Reclassification from AOCI, tax	21,167	(1,785)	(8,867)
Reclassification from AOCI, net of tax	(67,027)	5,650	28,077
Other comprehensive income (loss), before tax	(88,194)
Other comprehensive income (loss), tax	21,167
Total other comprehensive income (loss), net of tax	(67,027)
FSIRS
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, before tax	(2,719)
Beginning balance, tax	651
Beginning balance	(2,068)
Beginning balance, attributable to parent, before tax	(2,719)
Beginning balance, attributable to parent, tax	651
Beginning balance, attributable to parent	(2,068)
Reclassification from AOCI, before Tax	2,174	3,247	3,344
Reclassification from AOCI, tax	(522)	(780)	(803)
Reclassification from AOCI, net of tax	1,652	2,467	2,541
Other comprehensive income (loss), before tax	2,174	3,247	3,344
Other comprehensive income (loss), tax	(522)	(780)	(803)
Total other comprehensive income (loss), net of tax	1,652	2,467	2,541
Ending balance, attributable to parent, before tax	(545)	(2,719)		(2,719)
Ending balance, attributable to parent, tax	129	651		651
Ending balance, attributable to parent	(416)	(2,068)		(2,068)
Ending balance, before tax	(545)	(2,719)		(2,719)
Ending balance, tax	129	651		651
Ending balance	(416)	(2,068)		(2,068)
Foreign Currency Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, before tax	132
Beginning balance	132
Other comprehensive income (loss) before reclassifications, before tax	20
Other comprehensive income (loss) before reclassifications, net of tax	20
Ending balance, before tax	152	132		132
Ending balance	152	132		132
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications, net of tax	14,242
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(61,135)	(55,151)	(49,049)
Beginning balance, attributable to parent	(61,135)
Ending balance, attributable to parent	(46,913)	(61,135)		(61,135)
Ending balance	$ (46,913)	$ (61,135)	$ (55,151)	$ (61,135)

Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - Amount Recognized Before Income Tax Associated with Defined Benefit Plans in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Equity [Abstract]
Net actuarial loss	$ (399,010)	$ (502,783)
Prior service cost	(1,528)	(2,487)
Less: amount recognized in regulatory assets	339,356	427,550
Recognized in AOCI	$ (61,182)	$ (77,720)

Common Stock (Detail) - USD ($)	12 Months Ended			20 Months Ended
Common Stock (Detail) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Oct. 10, 2021	Apr. 08, 2021
Class of Stock [Line Items]
Net proceeds	$ 213,641,000	$ 139,245,000	$ 157,946,000
Shares registered and available for issuance (in shares)	4,300,000
Number of preferred stock purchase right, per share of common stock dividend (in shares)					1
Common stock, par (in USD per share)	$ 1	$ 1		$ 1
Purchase price per unit (in USD per share)					$ 321.70
Preferred stock purchase price, exercisable term, beneficial ownership percentage benchmark					10.00%
Preferred stock purchase price, exercisable term, beneficial ownership percentage benchmark with passive institutional investor					20.00%
Restricted Stock/Unit Plan and Management Incentive Plan
Class of Stock [Line Items]
Common stock issued (in shares)	48,000
Dividend Reinvestment and Stock Purchase Plan
Class of Stock [Line Items]
Common stock issued (in shares)	173,000
Common stock issuances	$ 11,800,000
Equity Shelf Program
Class of Stock [Line Items]
Sale of stock, amount of common stock offered for sale (up to)	$ 341,819,657					$ 500,000,000
Gross proceeds				$ 158,180,343
Less: agent commissions				(1,581,803)
Net proceeds				$ 156,598,540
Number of shares sold (in shares)				2,302,407
Weighted average price per share (USD per share)				$ 68.70

Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Aug. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt	$ 690,351
Less: current maturities	(275,000)		$ 0
Long-term debt, less current maturities	$ 2,440,603		2,438,206
Notes, 6.1%, due 2041
Debt Instrument [Line Items]
Debt instrument, stated interest rate	6.10%
Notes, 3.875%, due 2022
Debt Instrument [Line Items]
Debt instrument, stated interest rate	3.875%
Notes, 4.875%, due 2043
Debt Instrument [Line Items]
Debt instrument, stated interest rate	4.875%
Notes, 3.8%, due 2046
Debt Instrument [Line Items]
Debt instrument, stated interest rate	3.80%
Notes, 3.7%, due 2028
Debt Instrument [Line Items]
Debt instrument, stated interest rate	3.70%
Notes, 4.15%, due 2049
Debt Instrument [Line Items]
Debt instrument, stated interest rate	4.15%
Notes, 2.2%, due 2030
Debt Instrument [Line Items]
Debt instrument, stated interest rate	2.20%
Notes 3.18%, due 2051
Debt Instrument [Line Items]
Debt instrument, stated interest rate	3.18%	3.18%
8% Series, due 2026
Debt Instrument [Line Items]
Debt instrument, stated interest rate	8.00%
Medium-term notes, 7.78% series, due 2022
Debt Instrument [Line Items]
Debt instrument, stated interest rate	7.78%
Medium-term notes, 7.92% series, due 2027
Debt Instrument [Line Items]
Debt instrument, stated interest rate	7.92%
Medium-term notes, 6.76% series, due 2027
Debt Instrument [Line Items]
Debt instrument, stated interest rate	6.76%
MountainWest unsecured senior notes, 3.53%, due in 2028
Debt Instrument [Line Items]
Debt instrument, stated interest rate	3.53%
MountainWest unsecured senior notes, 4.875%, due in 2041
Debt Instrument [Line Items]
Debt instrument, stated interest rate	4.875%
MountainWest unsecured senior notes, 3.91%, due in 2038
Debt Instrument [Line Items]
Debt instrument, stated interest rate	3.91%
Debentures
Debt Instrument [Line Items]
Long-term debt	$ 350,000
Revolving credit facility and commercial paper
Debt Instrument [Line Items]
Long-term debt	130,000
Secured Debt \| Centuri secured revolving credit facility
Debt Instrument [Line Items]
Long-term debt	103,329
Secured Debt \| Centuri secured term loan facility
Debt Instrument [Line Items]
Long-term debt	57,250
Other debt obligations
Debt Instrument [Line Items]
Long-term debt	49,772
Carrying Amount
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(24,466)		(820)
Less: current maturities	(22,324)		(40,433)
Long-term debt, less current maturities	4,115,684		2,732,200
Carrying Amount \| Debentures
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(19,959)		(17,822)
Long-term debt	2,387,541		2,089,678
Carrying Amount \| Debentures \| Notes, 6.1%, due 2041
Debt Instrument [Line Items]
Long-term debt, gross	125,000		125,000
Carrying Amount \| Debentures \| Notes, 3.875%, due 2022
Debt Instrument [Line Items]
Long-term debt, gross	250,000		250,000
Carrying Amount \| Debentures \| Notes, 4.875%, due 2043
Debt Instrument [Line Items]
Long-term debt, gross	250,000		250,000
Carrying Amount \| Debentures \| Notes, 3.8%, due 2046
Debt Instrument [Line Items]
Long-term debt, gross	300,000		300,000
Carrying Amount \| Debentures \| Notes, 3.7%, due 2028
Debt Instrument [Line Items]
Long-term debt, gross	300,000		300,000
Carrying Amount \| Debentures \| Notes, 4.15%, due 2049
Debt Instrument [Line Items]
Long-term debt, gross	300,000		300,000
Carrying Amount \| Debentures \| Notes, 2.2%, due 2030
Debt Instrument [Line Items]
Long-term debt, gross	450,000		450,000
Carrying Amount \| Debentures \| Notes 3.18%, due 2051
Debt Instrument [Line Items]
Long-term debt, gross	300,000		0
Carrying Amount \| Debentures \| 8% Series, due 2026
Debt Instrument [Line Items]
Long-term debt, gross	75,000		75,000
Carrying Amount \| Debentures \| Medium-term notes, 7.78% series, due 2022
Debt Instrument [Line Items]
Long-term debt, gross	25,000		25,000
Carrying Amount \| Debentures \| Medium-term notes, 7.92% series, due 2027
Debt Instrument [Line Items]
Long-term debt, gross	25,000		25,000
Carrying Amount \| Debentures \| Medium-term notes, 6.76% series, due 2027
Debt Instrument [Line Items]
Long-term debt, gross	7,500		7,500
Carrying Amount \| Revolving credit facility and commercial paper
Debt Instrument [Line Items]
Long-term debt	130,000		150,000
Carrying Amount \| Industrial development revenue bonds
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(1,938)		(1,472)
Long-term debt	198,062		198,528
Carrying Amount \| Industrial development revenue bonds \| Tax-exempt Series A, due 2028
Debt Instrument [Line Items]
Long-term debt, gross	50,000		50,000
Carrying Amount \| Industrial development revenue bonds \| 2003 Series A, due 2038
Debt Instrument [Line Items]
Long-term debt, gross	50,000		50,000
Carrying Amount \| Industrial development revenue bonds \| 2008 Series A, due 2038
Debt Instrument [Line Items]
Long-term debt, gross	50,000		50,000
Carrying Amount \| Industrial development revenue bonds \| 2009 Series A, due 2039
Debt Instrument [Line Items]
Long-term debt, gross	50,000		50,000
Carrying Amount \| Secured Debt \| Centuri secured revolving credit facility
Debt Instrument [Line Items]
Long-term debt, gross	103,329		26,626
Carrying Amount \| Secured Debt \| Centuri secured term loan facility
Debt Instrument [Line Items]
Long-term debt, gross	1,117,138		226,648
Carrying Amount \| Unsecured Debt \| MountainWest unsecured senior notes, 3.53%, due in 2028
Debt Instrument [Line Items]
Long-term debt, gross	102,078		0
Carrying Amount \| Unsecured Debt \| MountainWest unsecured senior notes, 4.875%, due in 2041
Debt Instrument [Line Items]
Long-term debt, gross	199,926		0
Carrying Amount \| Unsecured Debt \| MountainWest unsecured senior notes, 3.91%, due in 2038
Debt Instrument [Line Items]
Long-term debt, gross	147,735		0
Carrying Amount \| Other debt obligations
Debt Instrument [Line Items]
Long-term debt, gross	51,665		81,973
Fair Value \| Debentures \| Notes, 6.1%, due 2041
Debt Instrument [Line Items]
Long-term debt, gross	166,380		174,858
Fair Value \| Debentures \| Notes, 3.875%, due 2022
Debt Instrument [Line Items]
Long-term debt, gross	250,603		258,825
Fair Value \| Debentures \| Notes, 4.875%, due 2043
Debt Instrument [Line Items]
Long-term debt, gross	307,538		317,190
Fair Value \| Debentures \| Notes, 3.8%, due 2046
Debt Instrument [Line Items]
Long-term debt, gross	329,055		347,046
Fair Value \| Debentures \| Notes, 3.7%, due 2028
Debt Instrument [Line Items]
Long-term debt, gross	325,191		344,553
Fair Value \| Debentures \| Notes, 4.15%, due 2049
Debt Instrument [Line Items]
Long-term debt, gross	342,030		370,278
Fair Value \| Debentures \| Notes, 2.2%, due 2030
Debt Instrument [Line Items]
Long-term debt, gross	440,838		474,552
Fair Value \| Debentures \| Notes 3.18%, due 2051
Debt Instrument [Line Items]
Long-term debt, gross	292,116		0
Fair Value \| Debentures \| 8% Series, due 2026
Debt Instrument [Line Items]
Long-term debt, gross	92,623		99,723
Fair Value \| Debentures \| Medium-term notes, 7.78% series, due 2022
Debt Instrument [Line Items]
Long-term debt, gross	25,122		26,663
Fair Value \| Debentures \| Medium-term notes, 7.92% series, due 2027
Debt Instrument [Line Items]
Long-term debt, gross	31,555		33,802
Fair Value \| Debentures \| Medium-term notes, 6.76% series, due 2027
Debt Instrument [Line Items]
Long-term debt, gross	8,949		9,613
Fair Value \| Revolving credit facility and commercial paper
Debt Instrument [Line Items]
Long-term debt	130,000		150,000
Fair Value \| Industrial development revenue bonds \| Tax-exempt Series A, due 2028
Debt Instrument [Line Items]
Long-term debt, gross	50,000		50,000
Fair Value \| Industrial development revenue bonds \| 2003 Series A, due 2038
Debt Instrument [Line Items]
Long-term debt, gross	50,000		50,000
Fair Value \| Industrial development revenue bonds \| 2008 Series A, due 2038
Debt Instrument [Line Items]
Long-term debt, gross	50,000		50,000
Fair Value \| Industrial development revenue bonds \| 2009 Series A, due 2039
Debt Instrument [Line Items]
Long-term debt, gross	50,000		50,000
Fair Value \| Secured Debt \| Centuri secured revolving credit facility
Debt Instrument [Line Items]
Long-term debt, gross	103,749		26,645
Fair Value \| Secured Debt \| Centuri secured term loan facility
Debt Instrument [Line Items]
Long-term debt, gross	1,117,841		230,824
Fair Value \| Unsecured Debt \| MountainWest unsecured senior notes, 3.53%, due in 2028
Debt Instrument [Line Items]
Long-term debt, gross	102,078		0
Fair Value \| Unsecured Debt \| MountainWest unsecured senior notes, 4.875%, due in 2041
Debt Instrument [Line Items]
Long-term debt, gross	199,926		0
Fair Value \| Unsecured Debt \| MountainWest unsecured senior notes, 3.91%, due in 2038
Debt Instrument [Line Items]
Long-term debt, gross	147,735		0
Fair Value \| Other debt obligations
Debt Instrument [Line Items]
Long-term debt, gross	$ 50,003		$ 84,246

Debt - Narrative (Details)				1 Months Ended		3 Months Ended		12 Months Ended
Debt - Narrative (Details)	Mar. 01, 2022 USD ($)	Nov. 01, 2021	Apr. 10, 2020	Nov. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) instrument	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) instrument	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2023	Dec. 31, 2022	Dec. 28, 2021 USD ($)	Dec. 27, 2021 USD ($)	Aug. 31, 2021 USD ($)	Aug. 27, 2021 USD ($)	Aug. 26, 2021 USD ($)
Debt Instrument [Line Items]
Long-term debt						$ 690,351,000		$ 690,351,000
Number of private placement unsecured senior notes \| instrument						2		2
Debt covenant, additional debt amount could be issued								$ 320,000,000
Debt covenant, equity cushion relating to minimum net worth requirement								2,000,000,000
Debt covenant, equity cushion relating to minimum fixed charge ratio coverage requirement								$ 181,000,000
Debt covenant, dividend restriction calculation, percentage of net income						50.00%		50.00%
Debt covenant, dividend restriction calculation, period								12 months
Short-term debt						$ 250,000,000		$ 250,000,000	$ 57,000,000
Current maturities of long-term debt						275,000,000		275,000,000	0
Issuance of long-term debt, net								297,318,000	446,508,000	$ 297,222,000
Subsequent Event
Debt Instrument [Line Items]
Proceeds from issuance of bonds	$ 600,000,000
Questar Pipelines
Debt Instrument [Line Items]
Debt instrument face amount						430,000,000		430,000,000
Long-term debt						$ 449,700,000		$ 449,700,000
Minimum \| Subsequent Event
Debt Instrument [Line Items]
Proceeds from issuance of equity and equity-linked instruments	900,000,000
Issuance of long-term debt, net	600,000,000
Minimum \| Questar Pipelines
Debt Instrument [Line Items]
Debt instrument, stated interest rate						3.53%		3.53%
Maximum \| Subsequent Event
Debt Instrument [Line Items]
Proceeds from issuance of equity and equity-linked instruments	1,000,000,000
Issuance of long-term debt, net	$ 700,000,000
Maximum \| Questar Pipelines
Debt Instrument [Line Items]
Debt instrument, stated interest rate						4.875%		4.875%
Notes 3.18%, due 2051
Debt Instrument [Line Items]
Debt instrument face amount															$ 300,000,000
Debt instrument, stated interest rate						3.18%		3.18%							3.18%
Debt instrument discount rate															0.019%
Centuri secured term loan facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity																$ 1,145,000,000
Debt instrument face amount																	$ 590,000,000
Debt instrument discount rate																1.00%
Centuri secured term loan facility \| Alternative Base Rate
Debt Instrument [Line Items]
Debt, basis spread on variable rate								1.50%
Centuri secured term loan facility \| LIBOR
Debt Instrument [Line Items]
Debt floor interest rate								0.50%
Centuri secured term loan facility \| LIBOR \| Minimum
Debt Instrument [Line Items]
Debt, basis spread on variable rate								2.50%
Centuri Secured Term Loan Facility and Revolving Credit Facility
Debt Instrument [Line Items]
Borrowings outstanding under facility						$ 1,220,000,000		$ 1,220,000,000
Effective interest rates						3.00%		3.00%
Centuri Secured Term Loan Facility and Revolving Credit Facility \| Minimum
Debt Instrument [Line Items]
Commitment fee percentage								0.15%
Centuri Secured Term Loan Facility and Revolving Credit Facility \| Maximum
Debt Instrument [Line Items]
Commitment fee percentage								0.35%
Centuri Secured Term Loan Facility and Revolving Credit Facility \| LIBOR
Debt Instrument [Line Items]
Borrowings outstanding under facility						$ 3,200,000,000		$ 3,200,000,000
Notes, 6.1%, due 2041
Debt Instrument [Line Items]
Debt instrument, stated interest rate						6.10%		6.10%
$250 Million Term Loan
Debt Instrument [Line Items]
Debt covenant, ratio of funded debt to total capitalization						0.70		0.70
Debt instrument face amount					$ 250,000,000		$ 250,000,000
Weighted average interest rate						0.80%		0.80%
$250 Million Term Loan \| Alternative Base Rate
Debt Instrument [Line Items]
Debt, basis spread on variable rate					0.00%
$250 Million Term Loan \| LIBOR
Debt Instrument [Line Items]
Borrowings outstanding under facility						$ 250,000,000		$ 250,000,000
$250 Million Term Loan \| LIBOR \| Minimum
Debt Instrument [Line Items]
Debt, basis spread on variable rate					0.55%
$250 Million Term Loan \| LIBOR \| Maximum
Debt Instrument [Line Items]
Debt, basis spread on variable rate					1.00%
Term Loan Facility due December 30, 2022
Debt Instrument [Line Items]
Short-term debt						1,909,000,000		1,909,000,000
Current maturities of long-term debt						$ 297,000,000		$ 297,000,000
Term Loan Facility due December 30, 2022 \| Loans Payable
Debt Instrument [Line Items]
Weighted average interest rate						1.354%		1.354%
Change intervals of basis spread on variable rate				0.25%
Debt term, mandatory prepayment as percentage of cash proceeds received				100.00%
Debt term, percentage of committed amount under specific acquisition financings				100.00%
Term Loan Facility due December 30, 2022 \| Questar Pipelines \| Loans Payable
Debt Instrument [Line Items]
Line of credit designated for working capital purposes				$ 1,500,000,000
Debt instrument face amount				$ 1,600,000,000
Debt covenant, additional debt amount could be issued								$ 1,000,000,000
Debt Instrument, term				364 days
Term Loan Facility due December 30, 2022 \| Minimum \| Loans Payable
Debt Instrument [Line Items]
Commitment fee percentage				0.06%
Term Loan Facility due December 30, 2022 \| Maximum \| Loans Payable
Debt Instrument [Line Items]
Commitment fee percentage				0.175%
Term Loan Facility due December 30, 2022 \| Alternative Base Rate \| Minimum \| Loans Payable
Debt Instrument [Line Items]
Debt, basis spread on variable rate				0.00%
Term Loan Facility due December 30, 2022 \| Alternative Base Rate \| Maximum \| Loans Payable
Debt Instrument [Line Items]
Debt, basis spread on variable rate				0.50%
Term Loan Facility due December 30, 2022 \| LIBOR \| Minimum \| Loans Payable
Debt Instrument [Line Items]
Debt, basis spread on variable rate				0.75%
Term Loan Facility due December 30, 2022 \| LIBOR \| Maximum \| Loans Payable
Debt Instrument [Line Items]
Debt, basis spread on variable rate				1.50%
Line of Credit \| LIBOR
Debt Instrument [Line Items]
Borrowings outstanding under facility						$ 130,000,000		130,000,000
$400 Million Credit Facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity						400,000,000		400,000,000
Line of credit designated as long term debt						150,000,000		150,000,000
Line of credit designated for working capital purposes						250,000,000		250,000,000
Long-term debt						$ 130,000,000		$ 130,000,000
Effective interest rates						1.24%		1.24%
Minimum amount outstanding during period								$ 0
Maximum amount outstanding during period							$ 275,000,000
Debt covenant, ratio of funded debt to total capitalization						0.70		0.70
Short-term debt						$ 0		$ 0	57,000,000
Weighted average interest rate						1.10%		1.10%
$400 Million Credit Facility \| Minimum
Debt Instrument [Line Items]
Commitment fee percentage			0.075%
$400 Million Credit Facility \| Maximum
Debt Instrument [Line Items]
Commitment fee percentage			0.20%
$400 Million Credit Facility \| SOFR
Debt Instrument [Line Items]
Debt, basis spread on variable rate								1.125%
$400 Million Credit Facility \| SOFR \| Minimum
Debt Instrument [Line Items]
Debt, basis spread on variable rate			0.75%
$400 Million Credit Facility \| SOFR \| Maximum
Debt Instrument [Line Items]
Debt, basis spread on variable rate			1.50%
$400 Million Credit Facility \| Alternative Base Rate
Debt Instrument [Line Items]
Debt, basis spread on variable rate								0.125%
$400 Million Credit Facility \| Alternative Base Rate \| Minimum
Debt Instrument [Line Items]
Debt, basis spread on variable rate			0.00%
$400 Million Credit Facility \| Alternative Base Rate \| Maximum
Debt Instrument [Line Items]
Debt, basis spread on variable rate			0.50%
Commercial Paper Program
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity						$ 50,000,000		$ 50,000,000
Borrowings outstanding under facility						0		0
Revolving Credit Facility \| Line of Credit
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity																$ 400,000,000
Minimum amount outstanding during period						103,000,000
Maximum amount outstanding during period						116,000,000
Assets amount securing the facility						$ 2,500,000,000		$ 2,500,000,000
Debt covenant, net leverage ratio						5.50		5.50
Debt covenant, net leverage ratio with certain material acquisitions						4.50		4.50
Debt covenant, minimum interest coverage ratio						2.50		2.50
Revolving Credit Facility \| Line of Credit \| Forecast
Debt Instrument [Line Items]
Debt covenant, net leverage ratio											4.00	4.75
Revolving Credit Facility \| Line of Credit \| Alternative Base Rate \| Minimum
Debt Instrument [Line Items]
Debt, basis spread on variable rate								0.00%
Revolving Credit Facility \| Line of Credit \| Alternative Base Rate \| Maximum
Debt Instrument [Line Items]
Debt, basis spread on variable rate								1.25%
Revolving Credit Facility \| Line of Credit \| LIBOR \| Minimum
Debt Instrument [Line Items]
Debt, basis spread on variable rate								1.00%
Revolving Credit Facility \| Line of Credit \| LIBOR \| Maximum
Debt Instrument [Line Items]
Debt, basis spread on variable rate								2.25%
$100 Million Credit Facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity														$ 100,000,000
$200 Million Credit Facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity													$ 200,000,000
Minimum amount outstanding during period						$ 22,000,000
Maximum amount outstanding during period						59,000,000
Short-term debt						$ 59,000,000		$ 59,000,000	$ 50,000,000
Weighted average interest rate						1.323%		1.323%	1.225%
Line of credit facility, maximum commitment amount						$ 300,000,000		$ 300,000,000
$200 Million Credit Facility \| SOFR
Debt Instrument [Line Items]
Debt, basis spread on variable rate		1.25%
$200 Million Credit Facility \| Alternative Base Rate
Debt Instrument [Line Items]
Debt, basis spread on variable rate		0.25%

Debt - Summary of Effective Interest Rates on Variable-Rate IDRBs (Details)	Dec. 31, 2021	Dec. 31, 2020
2003 Series A, due 2038
Debt Instrument [Line Items]
Effective interest rates	0.91%	0.80%
2008 Series A, due 2038
Debt Instrument [Line Items]
Effective interest rates	0.90%	0.83%
2009 Series A, due 2039
Debt Instrument [Line Items]
Effective interest rates	0.88%	0.76%
Tax-exempt Series A, due 2028
Debt Instrument [Line Items]
Effective interest rates	0.92%	0.87%

Debt - Estimated Maturities of Long-Term Debt (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
2022	$ 297,324
2023	22,497
2024	22,735
2025	150,526
2026	197,269
Long-term debt	690,351
Debentures
Debt Instrument [Line Items]
2022	275,000
2023	0
2024	0
2025	0
2026	75,000
Long-term debt	350,000
Revolving credit facility and commercial paper
Debt Instrument [Line Items]
2022	0
2023	0
2024	0
2025	130,000
2026	0
Long-term debt	130,000
Secured Debt \| Centuri secured revolving credit facility
Debt Instrument [Line Items]
2022	0
2023	0
2024	0
2025	0
2026	103,329
Long-term debt	103,329
Secured Debt \| Centuri secured term loan facility
Debt Instrument [Line Items]
2022	11,450
2023	11,450
2024	11,450
2025	11,450
2026	11,450
Long-term debt	57,250
Other debt obligations
Debt Instrument [Line Items]
2022	10,874
2023	11,047
2024	11,285
2025	9,076
2026	7,490
Long-term debt	$ 49,772

Share-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 6,392	$ 5,294	$ 5,146
Compensation cost related to nonvested management incentive plan shares, performance shares, and restricted stock/units not yet recognized	$ 5,200
Compensation cost not yet recognized, period for recognition	1 year 8 months 12 days
Omnibus Incentive Plan \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance measurement period	3 years
Compensation expense	$ 3,400	$ 2,800	$ 2,300
Restricted Stock/Unit Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, granted (in shares)	188,000
Weighted average grant date fair value (in USD per share)	$ 65.38	$ 62.23	$ 81.75
Restricted Stock/Unit Plan \| Vesting Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	40.00%
Restricted Stock/Unit Plan \| Vesting Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	30.00%
Restricted Stock/Unit Plan \| Vesting Tranche Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	30.00%
Restricted Stock/Unit Plan \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, granted (in shares)	120,400

Share-Based Compensation - Schedule of Share-Based Plan Compensation Expense, Including Cash Award (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Share-based compensation plan expense, net of related tax benefits	$ 5,747	$ 4,816	$ 5,154
Share-based compensation plan related tax benefits	$ 1,815	$ 1,521	$ 1,627

Share-Based Compensation - Schedule of Nonvested Performance and Restricted Stock Unit Plans (Details) - Restricted Stock/Unit Plan - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Restricted Stock/ Units
Nonvested/unissued at beginning of year (in shares)	401,000
Granted (in shares)	188,000
Dividends (in shares)	10,000
Forfeited or expired (in shares)	(9,000)
Vested and issued (in shares)	(70,000)
Nonvested/unissued at year end (in shares)	520,000	401,000
Weighted- average grant date fair value
Beginning balance (in USD per share)	$ 62.23
Granted (in USD per share)	65.38	$ 62.23	$ 81.75
Forfeited or expired (in USD per share)	70.09
Vested and issued (in USD per share)	69.87
Ending balance (in USD per share)	$ 61.01	$ 62.23
Performance Shares
Restricted Stock/ Units
Granted (in shares)	120,400
Vested and issued (in shares)	(31,400)

Commitments and Contingencies (Details)	Dec. 31, 2021 USD ($)
Loss Contingencies [Line Items]
Self-insured retention amount associated with general liability claims	$ 750,000
Additional self-insured retention amount of general liability	4,000,000
Loss contingency, maximum	$ 5,000,000

Pension and Other Postretirement Benefits - Narrative (Details)	1 Months Ended	12 Months Ended
	Jan. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) plan	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Defined Benefit Plan Disclosure [Line Items]
EIP, percent of compensation deferred with match		50.00%
EIP, employer matching contribution, percent of match		3.50%
Employee investment plan cost		$ 6,100,000	$ 5,900,000	$ 5,700,000
Deferred compensation plan, maximum percentage of salary deferral		80.00%
Deferred compensation plan, matching percentage		5.00%
Deferred compensation plan, payment term, option one		10 years
Deferred compensation plan, payment term, option two		15 years
Deferred compensation plan, payment term, option three		20 years
Deferred Compensation Plan, percent of amount deferred with match		50.00%
Period of additional option to receive payment		5 years
Deferred compensation, percentage of multiple interest rate		150.00%
Increments of change to the discount rate		0.25%
Increase (decrease) of discount rate		0.25%	0.75%
Increase in weighted-average rate of compensation		0.25%
Future estimated funding amount		$ 59,000,000
Defined contribution plans, employer contribution amount	$ 50,000,000	9,000,000	$ 9,000,000	8,000,000
Pension funding during period		$ 102,000,000
Deferred compensation plan, percentage of contributions with matching		100.00%
Deferred compensation plan, vesting percentage of deferral		100.00%
Multiemployer plan, contributions by employer		$ 57,400,000	$ 44,300,000	$ 41,300,000
Multiemployer plan, special surcharges		$ 0
Multiemployer pension plans, number of critical plans \| plan		6
Qualified Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Future estimated funding amount		$ 56,000,000
PBOP \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Per capita cost of covered health care benefits medical rate trend assumption		6.00%
PBOP \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Per capita cost of covered health care benefits medical rate trend assumption		4.50%

Pension and Other Postretirement Benefits - Schedule of Assumptions Used (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.00%	2.75%
Weighted-average rate of compensation increase	3.25%	3.00%
Asset return assumption	6.50%	6.50%

Pension and Other Postretirement Benefits - Schedule of Amounts Recognized in Balance Sheet and Income Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in plan assets:
Market value of plan assets at beginning of year	$ 1,238,719
Market value of plan assets at end of year	1,418,211	$ 1,238,719
Qualified Retirement Plan
Change in benefit obligations:
Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO)	1,499,239	1,329,577
Service cost	41,159	34,299	$ 25,864
Interest cost	40,432	45,555	49,006
Actuarial loss (gain)	8,908	145,440
Benefits paid	(58,541)	(55,632)
Benefit obligation at end of year (PBO/PBO/APBO)	1,531,197	1,499,239	1,329,577
Change in plan assets:
Market value of plan assets at beginning of year	1,186,433	974,993
Actual return on plan assets	136,151	165,072
Employer contributions	102,000	102,000
Benefits paid	(58,541)	(55,632)
Market value of plan assets at end of year	1,366,043	1,186,433	974,993
Funded status at year end	$ (165,154)	$ (312,806)
Weighted-average assumptions (benefit obligation):
Discount rate	3.00%	2.75%
Weighted-average rate of compensation increase	3.25%	3.00%
SERP
Change in benefit obligations:
Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO)	$ 53,631	$ 47,397
Service cost	526	389	266
Interest cost	1,431	1,604	1,760
Actuarial loss (gain)	(3,244)	7,240
Benefits paid	(2,814)	(2,999)
Benefit obligation at end of year (PBO/PBO/APBO)	49,530	53,631	47,397
Change in plan assets:
Market value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	2,814	2,999
Benefits paid	(2,814)	(2,999)
Market value of plan assets at end of year	0	0	0
Funded status at year end	$ (49,530)	$ (53,631)
Weighted-average assumptions (benefit obligation):
Discount rate	3.00%	2.75%
Weighted-average rate of compensation increase	3.25%	3.00%
PBOP
Change in benefit obligations:
Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO)	$ 82,205	$ 76,111
Service cost	1,691	1,581	1,276
Interest cost	2,193	2,582	3,046
Actuarial loss (gain)	3,438	6,547
Benefits paid	(5,301)	(4,616)
Benefit obligation at end of year (PBO/PBO/APBO)	84,226	82,205	76,111
Change in plan assets:
Market value of plan assets at beginning of year	52,286	52,838
Actual return on plan assets	7,717	5,320
Employer contributions	0	0
Benefits paid	(7,835)	(5,872)
Market value of plan assets at end of year	52,168	52,286	$ 52,838
Funded status at year end	$ (32,058)	$ (29,919)
Weighted-average assumptions (benefit obligation):
Discount rate	3.00%	2.75%

Pension and Other Postretirement Benefits - Schedule of Accumulated Benefit Obligation (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Retirement plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 1,395,773	$ 1,367,179
SERP
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 46,885	$ 50,471

Pension and Other Postretirement Benefits - Schedule of Expected Benefit Payments (Details) $ in Millions	Dec. 31, 2021 USD ($)
Pension
Defined Benefit Plan Disclosure [Line Items]
2022	$ 62.0
2023	64.0
2024	65.0
2025	67.0
2026	68.0
2027-2031	365.0
SERP
Defined Benefit Plan Disclosure [Line Items]
2022	3.0
2023	3.0
2024	3.0
2025	3.0
2026	2.9
2027-2031	13.9
PBOP
Defined Benefit Plan Disclosure [Line Items]
2022	5.0
2023	5.2
2024	5.2
2025	5.2
2026	5.3
2027-2031	$ 27.3

Pension and Other Postretirement Benefits - Schedule of Net Periodic Benefit Cost and Weighted-Average Assumptions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ 57,397	$ 56,291	$ 42,465
Weighted-average assumptions (net benefit cost)
Discount rate	3.00%	2.75%
Expected return on plan assets	6.50%	6.50%
Weighted-average rate of compensation increase	3.25%	3.00%
Qualified Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 41,159	$ 34,299	25,864
Interest cost	40,432	45,555	49,006
Expected return on plan assets	(72,352)	(65,296)	(60,244)
Amortization of prior service cost	0	0	0
Amortization of net actuarial loss	41,955	36,025	22,356
Net periodic benefit cost	$ 51,194	$ 50,583	$ 36,982
Weighted-average assumptions (net benefit cost)
Discount rate	2.75%	3.50%	4.50%
Expected return on plan assets	6.50%	6.75%	7.00%
Weighted-average rate of compensation increase	3.00%	3.25%	3.25%
SERP
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 526	$ 389	$ 266
Interest cost	1,431	1,604	1,760
Expected return on plan assets	0	0	0
Amortization of prior service cost	0	0	0
Amortization of net actuarial loss	2,642	1,805	1,020
Net periodic benefit cost	$ 4,599	$ 3,798	$ 3,046
Weighted-average assumptions (net benefit cost)
Discount rate	2.75%	3.50%	4.50%
Weighted-average rate of compensation increase	3.00%	3.25%	3.25%
PBOP
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,691	$ 1,581	$ 1,276
Interest cost	2,193	2,582	3,046
Expected return on plan assets	(3,239)	(3,408)	(3,156)
Amortization of prior service cost	959	1,155	1,271
Amortization of net actuarial loss	0	0	0
Net periodic benefit cost	$ 1,604	$ 1,910	$ 2,437
Weighted-average assumptions (net benefit cost)
Discount rate	2.75%	3.50%	4.50%
Expected return on plan assets	6.50%	6.75%	7.00%

Pension and Other Postretirement Benefits - Schedule of Other Changes in Plan Assets and Benefit Obligations Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	$ (59,176)	$ 57,539	$ 71,087
Amortization of prior service cost	(959)	(1,155)	(1,271)
Amortization of net actuarial loss	(44,597)	(37,830)	(23,376)
Prior service cost	0	0	1,878
Regulatory adjustment	88,194	(7,435)	(36,944)
Recognized in other comprehensive (income) loss	(16,538)	11,119	11,374
Net periodic benefit costs recognized in net income	57,397	56,291	42,465
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss	40,859	67,410	53,839
Qualified Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	(54,892)	45,665	66,557
Amortization of prior service cost	0	0	0
Amortization of net actuarial loss	(41,955)	(36,025)	(22,356)
Prior service cost	0	0	0
Regulatory adjustment	86,196	(3,956)	(39,782)
Recognized in other comprehensive (income) loss	(10,651)	5,684	4,419
Net periodic benefit costs recognized in net income	51,194	50,583	36,982
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss	40,543	56,267	41,401
SERP
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	(3,245)	7,240	7,975
Amortization of prior service cost	0	0	0
Amortization of net actuarial loss	(2,642)	(1,805)	(1,020)
Prior service cost	0	0	0
Regulatory adjustment	0	0	0
Recognized in other comprehensive (income) loss	(5,887)	5,435	6,955
Net periodic benefit costs recognized in net income	4,599	3,798	3,046
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss	(1,288)	9,233	10,001
PBOP
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	(1,039)	4,634	(3,445)
Amortization of prior service cost	(959)	(1,155)	(1,271)
Amortization of net actuarial loss	0	0	0
Prior service cost	0	0	1,878
Regulatory adjustment	1,998	(3,479)	2,838
Recognized in other comprehensive (income) loss	0	0	0
Net periodic benefit costs recognized in net income	1,604	1,910	2,437
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss	$ 1,604	$ 1,910	$ 2,437

Pension and Other Postretirement Benefits - Schedule of Fair Value of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	$ 1,418,211	$ 1,238,719
Equity Securities \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	25.00%
Equity Securities \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	75.00%
Fair Value, Inputs, Level 1 and 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	$ 1,415,748	1,236,134
Level 1 – Quoted prices in active markets for identical financial assets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	35,194	30,358
Level 1 – Quoted prices in active markets for identical financial assets \| Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	35,194	30,358
Level 2 – Significant other observable inputs
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1,380,554	1,205,776
Level 2 – Significant other observable inputs \| Global
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	378,474	329,962
Level 2 – Significant other observable inputs \| International
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	160,384	143,853
Level 2 – Significant other observable inputs \| U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	282,448	227,425
Level 2 – Significant other observable inputs \| Emerging markets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	82,999	78,070
Level 2 – Significant other observable inputs \| Private commingled fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	469,572	419,706
Level 2 – Significant other observable inputs \| Pooled funds and mutual funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	6,479	6,555
Level 2 – Significant other observable inputs \| Government fixed income and mortgage backed securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	198	205
Insurance company general account contracts
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2,463	2,585
Qualified Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1,366,043	1,186,433	$ 974,993
Qualified Retirement Plan \| Fair Value, Inputs, Level 1 and 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1,363,580	1,183,848
Qualified Retirement Plan \| Level 1 – Quoted prices in active markets for identical financial assets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	0	0
Qualified Retirement Plan \| Level 1 – Quoted prices in active markets for identical financial assets \| Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	0	0
Qualified Retirement Plan \| Level 2 – Significant other observable inputs
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1,363,580	1,183,848
Qualified Retirement Plan \| Level 2 – Significant other observable inputs \| Global
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	373,936	324,084
Qualified Retirement Plan \| Level 2 – Significant other observable inputs \| International
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	158,461	141,290
Qualified Retirement Plan \| Level 2 – Significant other observable inputs \| U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	279,062	223,374
Qualified Retirement Plan \| Level 2 – Significant other observable inputs \| Emerging markets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	82,004	76,679
Qualified Retirement Plan \| Level 2 – Significant other observable inputs \| Private commingled fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	463,942	412,230
Qualified Retirement Plan \| Level 2 – Significant other observable inputs \| Pooled funds and mutual funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	5,979	5,990
Qualified Retirement Plan \| Level 2 – Significant other observable inputs \| Government fixed income and mortgage backed securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	196	201
Qualified Retirement Plan \| Insurance company general account contracts
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2,463	2,585
PBOP
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	52,168	52,286	$ 52,838
PBOP \| Fair Value, Inputs, Level 1 and 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	52,168	52,286
PBOP \| Level 1 – Quoted prices in active markets for identical financial assets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	35,194	30,358
PBOP \| Level 1 – Quoted prices in active markets for identical financial assets \| Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	35,194	30,358
PBOP \| Level 2 – Significant other observable inputs
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	16,974	21,928
PBOP \| Level 2 – Significant other observable inputs \| Global
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	4,538	5,878
PBOP \| Level 2 – Significant other observable inputs \| International
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1,923	2,563
PBOP \| Level 2 – Significant other observable inputs \| U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	3,386	4,051
PBOP \| Level 2 – Significant other observable inputs \| Emerging markets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	995	1,391
PBOP \| Level 2 – Significant other observable inputs \| Private commingled fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	5,630	7,476
PBOP \| Level 2 – Significant other observable inputs \| Pooled funds and mutual funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	500	565
PBOP \| Level 2 – Significant other observable inputs \| Government fixed income and mortgage backed securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2	4
PBOP \| Insurance company general account contracts
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	$ 0	$ 0

Income Taxes - Summary of Income Before Taxes and Noncontrolling Interest for Domestic and Foreign Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
U.S.	$ 221,507	$ 282,489	$ 261,525
Foreign	25,343	22,249	11,145
Income before income taxes	$ 216,473	$ 194,873	$ 198,144

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123384075&loc=d3e41242-110953

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(8))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

Income Taxes - Summary of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal	$ (3,643)	$ (4,678)	$ 4,109
State	(6,556)	(179)	250
Foreign	6,524	4,666	5,013
Total current income tax expense	(10,199)	(4,857)	4,359
Deferred:
Federal	36,842	38,561	29,543
State	2,695	2,051	1,071
Foreign	156	1,222	(1,907)
Total deferred income tax expense	39,537	40,612	30,614
Total income tax expense	$ 29,338	$ 35,755	$ 34,973

Income Taxes - Significant Components of Deferred Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred federal and state:
Total deferred federal and state	$ 39,589	$ 40,664	$ 30,860
Deferred ITC, net	(52)	(52)	(246)
Total deferred income tax expense	39,537	40,612	30,614
Property-related items
Deferred federal and state:
Total deferred federal and state	23,077	36,029	34,398
Purchased gas cost adjustments
Deferred federal and state:
Total deferred federal and state	73,613	(5,726)	3,834
Employee benefits
Deferred federal and state:
Total deferred federal and state	5,508	11,437	6,493
Regulatory adjustments
Deferred federal and state:
Total deferred federal and state	(10,101)	(9,885)	(11,962)
Deferred payroll taxes
Deferred federal and state:
Total deferred federal and state	(892)	(1,810)	0
Deferred revenue
Deferred federal and state:
Total deferred federal and state	6,021	588	822
Net operating loss
Deferred federal and state:
Total deferred federal and state	(59,119)	0	0
Alternative minimum tax
Deferred federal and state:
Total deferred federal and state	0	4,409	441
All other deferred
Deferred federal and state:
Total deferred federal and state	$ 7,503	$ 6,210	$ (2,344)

Income Taxes - Reconciliation of U.S Federal Statutory Rate to Consolidated Effective Tax Rate (Details)	12 Months Ended			36 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Income Taxes [Line Items]
U.S. federal statutory income tax rate	21.00%	21.00%	21.00%
Net state taxes	0.30%	1.70%	0.70%
Tax credits	(0.60%)	(0.70%)	(0.40%)
Company-owned life insurance	(0.90%)	(1.00%)	(1.90%)
Amortization of excess deferred taxes	(4.90%)	(1.30%)	(1.20%)
All other differences	(1.30%)	(1.40%)	(0.50%)
Consolidated effective income tax rate	13.60%	18.30%	17.70%	24.00%

Income Taxes - Summary of Income Before Taxes for Continuing and Discontinued Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total income before income taxes	$ 216,473	$ 194,873	$ 198,144

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Deferred income taxes for future amortization of ITC and excess deferred taxes	$ 101,133	$ 104,314
Deferred Tax Assets, Employee benefits	(4,671)	4,806
Employee benefits	39,181	39,907
Federal net operating losses	59,119	0
Deferred payroll taxes	892	1,810
Lease-related item	18,462	20,890
Other	6,777	7,790
Valuation allowance	(22)	(22)
Deferred tax assets, total	163,228	118,698
Deferred tax liabilities:
Property-related items, including accelerated depreciation	703,374	680,294
Regulatory balancing accounts	77,818	4,205
Debt-related costs	2,277	2,585
Intangibles	97,860	13,511
Lease-related item	17,254	19,789
Other	18,587	12,714
Deferred tax liabilities, gross	802,056	699,798
Net deferred tax liabilities	$ 638,828	$ 581,100

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at beginning of year	$ 1,793	$ 1,056
Gross increases – tax positions in prior period	310	506
Gross decreases – tax positions in prior period	0	0
Gross increases – current period tax positions	259	231
Gross decreases – current period tax positions	0	0
Settlements	0	0
Lapse in statute of limitations	0	0
Unrecognized tax benefits at end of year	$ 2,362	$ 1,793

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Line Items]
Deferred income taxes	$ 121,000	$ 455,000
Unrecognized tax benefits that, if recognized, would affect the effective tax rate	2,400,000
Tax-related interest income	21,000	$ 523,000	$ 0
Capital Loss Carryforward
Income Tax Disclosure [Line Items]
Tax credit carryforward	97,000
General Business Tax Credit Carryforward
Income Tax Disclosure [Line Items]
Tax credit carryforward	0
Federal
Income Tax Disclosure [Line Items]
Operating loss carryforward	449,000,000
Foreign
Income Tax Disclosure [Line Items]
Operating loss carryforward	28,500,000
State
Income Tax Disclosure [Line Items]
Operating loss carryforward	$ 197,600,000

Segment Information - Narrative (Details) - segment	12 Months Ended
Segment Information - Narrative (Details) - segment	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Number of reportable segments	3	2
Net Assets, Geographic Area \| Geographic Concentration Risk \| United States
Segment Reporting Information [Line Items]
Long-lived assets	99.00%

Segment Information - Accounts Receivable for Services (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Accounts receivable for Centuri services	$ 15,166	$ 13,956

- Definition

The aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due within one year (or one business cycle).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(C))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(11))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(B))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(a)(2))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=124098289&loc=d3e6676-107765

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(1))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Segment Information - Schedule of Revenues by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 3,680,451	$ 3,298,873	$ 3,119,917
United States
Segment Reporting Information [Line Items]
Revenues	3,411,018	3,057,041	2,893,201
Canada
Segment Reporting Information [Line Items]
Revenues	$ 269,433	$ 241,832	$ 226,716

Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 3,680,451	$ 3,298,873	$ 3,119,917
Interest income	5,113	4,015	6,356
Interest expense	97,560	101,148	95,026
Depreciation and amortization	253,398	235,295	215,620
Income tax expense	29,338	35,755	34,973
Segment net income	200,779	232,324	213,936
Segment assets	7,950,263	7,256,636	8,170,048
Capital expenditures	601,983	692,216	778,748
Operating Segments
Segment Reporting Information [Line Items]
Revenues	3,578,105	3,164,014	2,961,191
Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenues	102,346	134,859	158,726
Interest income	0	0	0
Interest expense	639	1,060	114
Depreciation and amortization	0	0	0
Income tax expense	(8,466)	(1,130)	(349)
Segment net income	(26,776)	(1,656)	(1,639)
Segment assets	47,664	3,980	6,108
Capital expenditures	0	0	0
Natural Gas Distribution
Segment Reporting Information [Line Items]
Revenues	1,521,790	1,350,585	1,368,939
Interest income	5,113	4,015	6,356
Interest expense	97,560	101,148	95,026
Depreciation and amortization	253,398	235,295	215,620
Income tax expense	29,338	35,755	34,973
Segment net income	187,135	159,118	163,171
Segment assets	7,950,263	7,256,636	6,798,746
Capital expenditures	601,983	692,216	778,748
Natural Gas Distribution \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	1,521,790	1,350,585	1,368,939
Interest income	5,113	4,015	6,356
Natural Gas Distribution \| Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenues	0	0	0
Utility Infrastructure Services
Segment Reporting Information [Line Items]
Revenues	2,158,661	1,948,288	1,750,978
Interest income	0	0	0
Interest expense	20,999	9,269	14,086
Depreciation and amortization	117,643	96,732	87,617
Income tax expense	18,776	31,128	21,399
Segment net income	40,420	74,862	52,404
Segment assets	2,579,748	1,475,237	1,365,194
Capital expenditures	113,643	132,889	159,400
Utility Infrastructure Services \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	2,056,315	1,813,429	1,592,252
Utility Infrastructure Services \| Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenues	102,346	$ 134,859	$ 158,726
Pipeline and Storage
Segment Reporting Information [Line Items]
Revenues	0
Interest income	0
Interest expense	0
Depreciation and amortization	0
Income tax expense	0
Segment net income	0
Segment assets	2,187,582
Capital expenditures	0
Pipeline and Storage \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	0
Pipeline and Storage \| Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenues	$ 0

Redeemable Noncontrolling Interests - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Nov. 30, 2018
Noncontrolling Interest [Line Items]
Percentage of interest retained by noncontrolling party subject to election		100.00%
Redemption value adjustment		$ 12,016	$ 74,513
Promissory Note \| Prime Rate
Noncontrolling Interest [Line Items]
Debt, basis spread on variable rate	2.00%
Linetec
Noncontrolling Interest [Line Items]
Ownership percentage by noncontrolling owners				20.00%
Redemption value adjustment		12,016	74,513
Drum
Noncontrolling Interest [Line Items]
Ownership percentage by noncontrolling owners	1.42%
Redemption value adjustment		$ 0	$ 0

Redeemable Noncontrolling Interests - Summary of Redeemable Noncontrolling Interest (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	$ 165,716	$ 84,542
Redeemable noncontrolling interest acquired	12,562
Net income attributable to redeemable noncontrolling interests	6,423	6,661
Redemption value adjustment	12,016	74,513
Ending balance	196,717	165,716
Linetec
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	165,716	84,542
Redeemable noncontrolling interest acquired	0
Net income attributable to redeemable noncontrolling interests	6,416	6,661
Redemption value adjustment	12,016	74,513
Ending balance	184,148	165,716
Drum
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	0	0
Redeemable noncontrolling interest acquired	12,562
Net income attributable to redeemable noncontrolling interests	7	0
Redemption value adjustment	0	0
Ending balance	$ 12,569	$ 0

Business Acquisitions - Narrative (Details) - USD ($)			1 Months Ended	3 Months Ended	4 Months Ended
Business Acquisitions - Narrative (Details) - USD ($)	Dec. 31, 2021	Aug. 27, 2021	Nov. 30, 2021	Dec. 31, 2021	Dec. 31, 2021
Drum
Business Acquisition [Line Items]
Ownership percentage by noncontrolling owners			1.42%
Drum
Business Acquisition [Line Items]
Payments to acquire business		$ 822,200,000
Cash acquired from acquisition		1,900,000
Acquired gross contractual receivable		81,000,000
Acquired contractual receivable deemed uncollectible		12,000,000
Accounts receivable measurement period adjustments					$ 8,600,000
Measurement period adjustments				$ 6,300,000	6,300,000
Working capital adjustments, period post-acquisition				60 days
Incurred and expensed acquisition costs		14,000,000
Goodwill tax-deductible amount		$ 76,000,000
Questar Pipelines
Business Acquisition [Line Items]
Payments to acquire business	$ 1,545,000,000
Measurement period adjustments	25,900,000
Incurred and expensed acquisition costs	18,500,000			$ 18,500,000	18,500,000
Goodwill tax-deductible amount	935,100,000			935,100,000	935,100,000
Business combination consideration	1,576,000,000
Business combination consideration, transaction costs paid on behalf of seller	4,700,000
Debt instrument face amount	$ 430,000,000			$ 430,000,000	$ 430,000,000
Questar Pipelines \| Term Loan Facility due December 30, 2022 \| Loans Payable
Business Acquisition [Line Items]
Debt instrument face amount			$ 1,600,000,000
Debt Instrument, term			364 days

Business Acquisitions - Summary of Assets Acquired and Liabilities Assumed - Drum Acquisition (Details) - USD ($) $ in Thousands	3 Months Ended	4 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Aug. 27, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 10,095	$ 10,095		$ 10,095	$ 343,023
Drum
Business Acquisition [Line Items]
Cash and cash equivalents	1,900	1,900	$ 1,900
Accounts receivable	60,500	60,500	69,100
Measurement Period Adjustments, Accounts receivable		(8,600)
Contract assets	47,500	47,500	40,100
Measurement Period Adjustments, Contract assets		7,400
Income taxes receivable, net	700	700	700
Right of use assets under operating leases	1,500	1,500	1,500
Prepaid and other current assets	5,200	5,200	5,200
Property and equipment	119,300	119,300	118,100
Measurement Period Adjustments, Property and equipment		1,200
Intangible assets	303,500	303,500	335,000
Measurement Period Adjustments, Intangible assets		(31,500)
Goodwill	449,500	449,500	446,800
Measurement Period Adjustments, Goodwill		2,700
Total assets acquired	989,600	989,600	1,018,400
Measurement Period Adjustments, Total assets acquired		(28,800)
Trade and other payables	46,200	46,200	46,200
Finance lease obligations	28,700	28,700	27,500
Measurement Period Adjustments, Finance lease obligations		1,200
Contract liabilities	12,700	12,700	12,700
Operating lease obligations	1,500	1,500	1,500
Other liabilities	5,000	5,000	5,300
Measurement Period Adjustments, Other liabilities		(300)
Deferred tax liabilities	71,400	71,400	94,800
Measurement Period Adjustments, Deferred tax liabilities		(23,400)
Total liabilities assumed and noncontrolling interest	165,500	165,500	188,000
Measurement Period Adjustments, Total liabilities assumed and noncontrolling interest		(22,500)
Net assets acquired	824,100	824,100	$ 830,400
Measurement Period Adjustments	$ (6,300)	$ (6,300)

Business Acquisitions - Major Class of Intangible Assets Acquired (Details) - Drum $ in Thousands	Aug. 27, 2021 USD ($)
Business Acquisition [Line Items]
Finite-lived intangibles acquired	$ 303,500
Order or Production Backlog
Business Acquisition [Line Items]
Finite-lived intangibles acquired	$ 4,500
Acquired intangible assets, weighted average useful life	1 year
Trade Names
Business Acquisition [Line Items]
Finite-lived intangibles acquired	$ 60,000
Acquired intangible assets, weighted average useful life	15 years
Customer relationships
Business Acquisition [Line Items]
Finite-lived intangibles acquired	$ 239,000
Acquired intangible assets, weighted average useful life	19 years

Business Acquisitions - Actual Operation Results for Riggs Distler (Details) - Drum $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)
Business Acquisition [Line Items]
Utility infrastructure services revenues	$ 163,830
Net income attributable to Southwest Gas Holdings, Inc.	$ 1,374

Business Acquisitions - Summary of Assets Acquired and Liabilities Assumed - Questar Acquisition (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 10,095	$ 10,095	$ 343,023
Questar Pipelines
Business Acquisition [Line Items]
Gas plant	1,047,400
Other property and investments	51,300
Cash and cash equivalents	17,600
Accounts receivable	26,600
Prepaid and other current assets	27,400
Deferred charges and other assets	31,100
Goodwill	986,200
Deferred income taxes	15,400
Total assets acquired	2,203,000
Long-term debt	449,700
Trade and other payables	7,000
Deferred purchased gas costs	5,700
Customer deposits	3,200
Accrued general taxes	400
Accrued interest	4,700
Other current liabilities	14,500
Accumulated removal costs	56,600
Other deferred credits	85,600
Total liabilities assumed and noncontrolling interest	627,400
Net assets acquired	$ 1,575,600

Business Acquisitions - Business Acquisition, Pro Forma Information (Details) - Questar Pipelines - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Business acquisition, pro forma adjustment, transaction costs		$ 48,700
Business acquisition, pro forma adjustment, transaction costs, incremental interest expense	$ 48,400	52,100
Total operating revenues	4,236	3,980
Net income (loss) attributable	$ 278	$ 276
Basic earnings per share (in USD per Share)	$ 4.70	$ 4.93
Diluted earnings per share (in USD per Share)	$ 4.69	$ 4.93