0001692115-20-000032 | 10-Q | XBRL Viewer | Southwest GAS Holdings INC

Cover - shares	3 Months Ended
Cover - shares	Mar. 31, 2020	Apr. 30, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-37976
Entity Registrant Name	Southwest Gas Holdings, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-3881866
Entity Address, Address Line One	5241 Spring Mountain Road
Entity Address, Address Line Two	Post Office Box 98510
Entity Address, City or Town	Las Vegas,
Entity Address, State or Province	NV
Entity Address, Postal Zip Code	89193-8510
City Area Code	(702)
Local Phone Number	876-7237
Title of 12(b) Security	Southwest Gas Holdings, Inc. Common Stock, $1 Par Value
Trading Symbol	SWX
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		55,129,976
Entity Central Index Key	0001692115
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false
Southwest Gas Corporation
Entity Information [Line Items]
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Entity File Number	1-7850
Entity Registrant Name	Southwest Gas Corporation
Entity Incorporation, State or Country Code	CA
Entity Tax Identification Number	88-0085720
Entity Address, Address Line One	5241 Spring Mountain Road
Entity Address, Address Line Two	Post Office Box 98510
Entity Address, City or Town	Las Vegas,
Entity Address, State or Province	NV
Entity Address, Postal Zip Code	89193-8510
City Area Code	(702)
Local Phone Number	876-7237
Trading Symbol	SWX
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Central Index Key	0000092416
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Utility plant:
Gas plant	$ 7,949,283	$ 7,813,221
Less: accumulated depreciation	(2,341,561)	(2,313,050)
Construction work in progress	202,935	185,026
Net utility plant	5,810,657	5,685,197
Other property and investments	785,522	784,173
Current assets:
Cash and cash equivalents	60,965	49,539
Accounts receivable, net of allowances	423,013	474,097
Accrued utility revenue	48,100	79,100
Income taxes receivable, net	7,503	31,751
Deferred purchased gas costs	0	44,412
Prepaid and other current assets	133,338	180,957
Total current assets	672,919	859,856
Noncurrent assets:
Goodwill	333,943	343,023
Deferred income taxes	765	856
Deferred charges and other assets	489,419	496,943
Total noncurrent assets	824,127	840,822
Total assets	8,093,225	8,170,048
Capitalization:
Common stock, $1 par (authorized - 120,000,000 shares; issued and outstanding - 55,126,386 and 55,007,433 shares)	56,756	56,637
Additional paid-in capital	1,470,411	1,466,937
Accumulated other comprehensive loss, net	(59,073)	(56,732)
Retained earnings	1,079,801	1,039,072
Total equity	2,547,895	2,505,914
Redeemable noncontrolling interest	85,005	84,542
Long-term debt, less current maturities	2,310,084	2,300,482
Total capitalization	4,942,984	4,890,938
Current liabilities:
Current maturities of long-term debt	169,574	163,512
Short-term debt	157,000	211,000
Accounts payable	182,182	238,921
Customer deposits	69,938	69,165
Income taxes payable, net	0	2,069
Accrued general taxes	73,105	48,160
Accrued interest	34,755	21,329
Deferred purchased gas costs	26,498	60,755
Other current liabilities	266,763	264,950
Total current liabilities	979,815	1,079,861
Deferred income taxes and other credits:
Deferred income taxes and investment tax credits, net	624,888	599,840
Accumulated removal costs	399,000	395,000
Other deferred credits and other long-term liabilities	1,146,538	1,204,409
Total deferred income taxes and other credits	2,170,426	2,199,249
Total capitalization and liabilities	8,093,225	8,170,048
Southwest Gas Corporation
Utility plant:
Gas plant	7,949,283	7,813,221
Less: accumulated depreciation	(2,341,561)	(2,313,050)
Construction work in progress	202,935	185,026
Net utility plant	5,810,657	5,685,197
Other property and investments	118,547	133,787
Current assets:
Cash and cash equivalents	56,524	40,489
Accounts receivable, net of allowances	148,817	150,793
Accrued utility revenue	48,100	79,100
Income taxes receivable, net	0	25,901
Deferred purchased gas costs	0	44,412
Prepaid and other current assets	119,264	165,639
Total current assets	372,705	506,334
Noncurrent assets:
Goodwill	10,095	10,095
Deferred charges and other assets	456,684	463,333
Total noncurrent assets	466,779	473,428
Total assets	6,768,688	6,798,746
Capitalization:
Common stock, $1 par (authorized - 120,000,000 shares; issued and outstanding - 55,126,386 and 55,007,433 shares)	49,112	49,112
Additional paid-in capital	1,279,208	1,229,083
Accumulated other comprehensive loss, net	(53,487)	(55,151)
Retained earnings	839,443	782,108
Total equity	2,114,276	2,005,152
Long-term debt, less current maturities	1,991,624	1,991,333
Total capitalization	4,105,900	3,996,485
Current liabilities:
Current maturities of long-term debt	125,000	125,000
Short-term debt	97,000	194,000
Accounts payable	108,569	149,368
Customer deposits	69,938	69,165
Income taxes payable, net	19,241	0
Accrued general taxes	73,105	48,160
Accrued interest	34,714	21,256
Deferred purchased gas costs	26,498	60,755
Payable to parent	174	844
Other current liabilities	147,950	126,573
Total current liabilities	702,189	795,121
Deferred income taxes and other credits:
Deferred income taxes and investment tax credits, net	547,281	539,050
Accumulated removal costs	399,000	395,000
Other deferred credits and other long-term liabilities	1,014,318	1,073,090
Total deferred income taxes and other credits	1,960,599	2,007,140
Total capitalization and liabilities	$ 6,768,688	$ 6,798,746

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
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)	55,126,386	55,007,433
Common stock, outstanding (in shares)	55,126,386	55,007,433

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Operating revenues:
Gas operating revenues	$ 502,827	$ 520,677	$ 1,351,089	$ 1,384,092
Utility infrastructure services revenues	333,493	312,862	1,771,609	1,575,130
Total operating revenues	836,320	833,539	3,122,698	2,959,222
Operating expenses:
Net cost of gas sold	160,821	192,604	353,381	426,260
Operations and maintenance	103,781	106,245	421,686	410,287
Depreciation and amortization	87,653	77,539	313,351	264,273
Taxes other than income taxes	16,378	16,206	62,500	60,847
Utility infrastructure services expenses	319,314	300,465	1,592,076	1,429,202
Total operating expenses	687,947	693,059	2,742,994	2,590,869
Operating income	148,373	140,480	379,704	368,353
Other income and (expenses):
Net interest deductions	(28,380)	(26,397)	(111,209)	(100,437)
Other income (deductions)	(20,770)	6,839	(17,524)	(6,253)
Total other income and (expenses)	(49,150)	(19,558)	(128,733)	(106,690)
Income before income taxes	99,223	120,922	250,971	261,663
Income tax expense	26,218	25,538	56,703	62,921
Net income	73,005	95,384	194,268	198,742
Net income attributable to noncontrolling interests	463	575	2,599	747
Net income attributable to Southwest Gas Holdings, Inc.	$ 72,542	$ 94,809	$ 191,669	$ 197,995
Earnings per share:
Basic (in USD per share)	$ 1.31	$ 1.78	$ 3.50	$ 3.91
Diluted (in USD per share)	$ 1.31	$ 1.77	$ 3.50	$ 3.91
Weighted average shares:
Basic (in shares)	55,310	53,369	54,726	50,640
Diluted (in shares)	55,363	53,424	54,792	50,701
Southwest Gas Corporation
Operating revenues:
Gas operating revenues	$ 502,827	$ 520,677	$ 1,351,089	$ 1,384,092
Operating expenses:
Net cost of gas sold	160,821	192,604	353,381	426,260
Operations and maintenance	103,088	105,542	419,720	408,165
Depreciation and amortization	64,725	57,612	222,733	199,467
Taxes other than income taxes	16,378	16,206	62,500	60,847
Total operating expenses	345,012	371,964	1,058,334	1,094,739
Operating income	157,815	148,713	292,755	289,353
Other income and (expenses):
Net interest deductions	(25,058)	(23,099)	(96,985)	(85,584)
Other income (deductions)	(20,536)	5,946	(16,965)	(6,691)
Total other income and (expenses)	(45,594)	(17,153)	(113,950)	(92,275)
Income before income taxes	112,221	131,560	178,805	197,078
Income tax expense	28,622	28,171	35,424	45,196
Net income	83,599	103,389	143,381	151,882
Net income attributable to Southwest Gas Holdings, Inc.	$ 83,599	$ 103,389	$ 143,381	$ 151,882

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Net income	$ 73,005	$ 95,384	$ 194,268	$ 198,742
Defined benefit pension plans:
Net actuarial loss	0	0	(54,026)	(15,524)
Amortization of prior service cost	220	241	945	1,002
Amortization of net actuarial loss	7,188	4,441	20,513	23,603
Prior service cost	0	0	(1,426)	0
Regulatory adjustment	(6,380)	(4,063)	25,760	(4,574)
Net defined benefit pension plans	1,028	619	(8,234)	4,507
Forward-starting interest rate swaps (“FSIRS”):
Amounts reclassified into net income	636	635	2,542	2,541
Net forward-starting interest rate swaps	636	635	2,542	2,541
Foreign currency translation adjustments	(4,005)	791	(2,758)	(1,308)
Total other comprehensive income (loss), net of tax	(2,341)	2,045	(8,450)	5,740
Comprehensive income	70,664	97,429	185,818	204,482
Comprehensive income attributable to noncontrolling interests	463	575	2,599	747
Comprehensive income attributable to Southwest Gas Holdings, Inc.	70,201	96,854	183,219	203,735
Southwest Gas Corporation
Net income	83,599	103,389	143,381	151,882
Defined benefit pension plans:
Net actuarial loss	0	0	(54,026)	(15,524)
Amortization of prior service cost	220	241	945	1,002
Amortization of net actuarial loss	7,188	4,441	20,513	23,603
Prior service cost	0	0	(1,426)	0
Regulatory adjustment	(6,380)	(4,063)	25,760	(4,574)
Net defined benefit pension plans	1,028	619	(8,234)	4,507
Forward-starting interest rate swaps (“FSIRS”):
Amounts reclassified into net income	636	635	2,542	2,541
Net forward-starting interest rate swaps	636	635	2,542	2,541
Total other comprehensive income (loss), net of tax	1,664	1,254	(5,692)	7,048
Comprehensive income	$ 85,263	$ 104,643	$ 137,689	$ 158,930

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	$ 73,005	$ 95,384	$ 194,268	$ 198,742
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	87,653	77,539	313,351	264,273
Deferred income taxes	25,309	24,923	54,548	52,736
Changes in current assets and liabilities:
Accounts receivable, net of allowances	45,837	(15,562)	7,154	(40,282)
Accrued utility revenue	31,000	30,200	(1,100)	300
Deferred purchased gas costs	10,155	(67,863)	19,527	25,339
Accounts payable	(60,723)	(12,643)	(49,945)	47,632
Accrued taxes	30,377	25,400	10,220	(5,331)
Other current assets and liabilities	76,453	47,848	102,742	(5,582)
Gains on sale of equipment	(28)	(233)	(5,268)	(1,706)
Changes in undistributed stock compensation	2,816	3,188	6,524	7,438
Equity AFUDC	(1,061)	(960)	(4,262)	(4,358)
Changes in deferred charges and other assets	6,495	(16,328)	1,772	(20,221)
Changes in other liabilities and deferred credits	(55,722)	(2,782)	(65,704)	17,420
Net cash provided by operating activities	271,566	188,111	583,827	536,400
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(210,655)	(210,662)	(938,141)	(822,034)
Acquisition of businesses, net of cash acquired	0	0	(47,638)	(247,164)
Changes in customer advances	5,434	3,078	21,357	13,503
Other	4,430	262	19,321	3,200
Net cash used in investing activities	(200,791)	(207,322)	(945,101)	(1,052,495)
CASH FLOW FROM FINANCING ACTIVITIES:
Issuance of common stock, net	3,148	25,879	135,215	369,061
Dividends paid	(30,006)	(27,602)	(118,531)	(104,003)
Issuance of long-term debt, net	99,978	29,666	601,908	259,456
Retirement of long-term debt	(75,168)	(31,160)	(257,797)	(247,816)
Change in credit facility and commercial paper	0	0	0	111,000
Change in short-term debt	(54,000)	36,000	(31,000)	165,500
Principal payments on finance lease obligations	(51)	(70)	(193)	(553)
Withholding remittance - share-based compensation	(2,736)	(1,838)	(2,756)	(2,096)
Other	(199)	(53)	(1,422)	(2,460)
Net cash provided by (used in) financing activities	(59,034)	30,822	325,424	548,089
Effects of currency translation on cash and cash equivalents	(315)	65	(222)	(72)
Change in cash and cash equivalents	11,426	11,676	(36,072)	31,922
Cash and cash equivalents at beginning of period	49,539	85,361	97,037	65,115
Cash and cash equivalents at end of period	60,965	97,037	60,965	97,037
SUPPLEMENTAL INFORMATION:
Interest paid, net of amounts capitalized	13,073	15,850	99,481	89,118
Income taxes paid (received), net	(20,064)	454	(17,766)	(2,743)
Southwest Gas Corporation
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	83,599	103,389	143,381	151,882
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	64,725	57,612	222,733	199,467
Deferred income taxes	7,707	26,270	15,118	50,593
Changes in current assets and liabilities:
Accounts receivable, net of allowances	1,975	(30,414)	21,652	(22,522)
Accrued utility revenue	31,000	30,200	(1,100)	300
Deferred purchased gas costs	10,155	(67,863)	19,527	25,339
Accounts payable	(41,899)	(39,574)	(29,798)	18,398
Accrued taxes	53,335	28,704	33,526	(17,504)
Other current assets and liabilities	99,257	81,625	106,803	(12,982)
Changes in undistributed stock compensation	2,496	2,597	5,045	5,834
Equity AFUDC	(1,061)	(960)	(4,262)	(4,358)
Changes in deferred charges and other assets	3,658	(18,238)	(9,871)	(23,289)
Changes in other liabilities and deferred credits	(55,910)	(2,977)	(66,294)	16,805
Net cash provided by operating activities	259,037	170,371	456,460	387,963
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(173,353)	(163,636)	(788,465)	(714,762)
Changes in customer advances	5,433	3,078	21,356	13,503
Other	(31)	(78)	(48)	(357)
Net cash used in investing activities	(167,951)	(160,636)	(767,157)	(701,616)
CASH FLOW FROM FINANCING ACTIVITIES:
Contributions from parent	50,000	22,842	187,094	136,391
Dividends paid	(25,200)	(23,500)	(97,600)	(89,500)
Issuance of long-term debt, net	0	0	297,222	0
Change in credit facility and commercial paper	0	0	0	111,000
Change in short-term debt	(97,000)	36,000	(91,000)	188,000
Withholding remittance - share-based compensation	(2,736)	(1,838)	(2,756)	(2,096)
Other	(115)	(53)	(887)	(783)
Net cash provided by (used in) financing activities	(75,051)	33,451	292,073	343,012
Change in cash and cash equivalents	16,035	43,186	(18,624)	29,359
Cash and cash equivalents at beginning of period	40,489	31,962	75,148	45,789
Cash and cash equivalents at end of period	56,524	75,148	56,524	75,148
SUPPLEMENTAL INFORMATION:
Interest paid, net of amounts capitalized	10,204	11,585	87,277	75,094
Income taxes paid (received), net	$ (22,962)	$ (22)	$ 700	$ (5,878)

CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Southwest Gas Corporation	Common Stock	Common Stock Southwest Gas Corporation	Additional paid-in capital	Additional paid-in capital Southwest Gas Corporation	Accumulated other comprehensive loss	Accumulated other comprehensive loss Southwest Gas Corporation	Retained Earnings	Retained Earnings Southwest Gas Corporation	Southwest Gas Holdings, Inc.	Non-controlling Interest
Beginning balance (in shares) at Dec. 31, 2018			53,026,000	47,482,000
Beginning balance at Dec. 31, 2018			$ 54,656	$ 49,112	$ 1,305,769	$ 1,065,242	$ (52,668)	$ (49,049)	$ 944,285	$ 717,155		$ (452)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)			365,000
Common stock issuances			$ 365		27,024
Net income									94,809	103,389
Foreign currency exchange translation adjustment							791
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax							619	619
FSIRS amounts reclassified to net income, net of tax	$ 635	$ 635					635	635
Share-based compensation						918				(160)
Dividends declared									(29,285)	(22,800)
Contributions from Southwest Gas Holdings, Inc.						22,842
Ending balance (in shares) at Mar. 31, 2019			53,391,000	47,482,000
Ending balance at Mar. 31, 2019	$ 2,346,548	1,887,903	$ 55,021	$ 49,112	1,332,793	1,089,002	(50,623)	(47,795)	1,009,809	797,584	$ 2,347,000	(452)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 0.545
FSIRS amounts reclassified to net income, net of tax	$ 2,542	2,542
Ending balance (in shares) at Mar. 31, 2020	55,126,386		55,126,000	47,482,000
Ending balance at Mar. 31, 2020	$ 2,547,895	2,114,276	$ 56,756	$ 49,112	1,470,411	1,279,208	(59,073)	(53,487)	1,079,801	839,443	2,547,895	0
Beginning balance (in shares) at Dec. 31, 2019	55,007,433		55,007,000	47,482,000
Beginning balance at Dec. 31, 2019			$ 56,637	$ 49,112	1,466,937	1,229,083	(56,732)	(55,151)	1,039,072	782,108		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)			119,000
Common stock issuances			$ 119		3,474
Net income									72,542	83,599
Foreign currency exchange translation adjustment							(4,005)
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax							1,028	1,028
FSIRS amounts reclassified to net income, net of tax	$ 636	636					636	636
Share-based compensation						125				(364)
Dividends declared									(31,813)	(25,900)
Contributions from Southwest Gas Holdings, Inc.						50,000
Ending balance (in shares) at Mar. 31, 2020	55,126,386		55,126,000	47,482,000
Ending balance at Mar. 31, 2020	$ 2,547,895	$ 2,114,276	$ 56,756	$ 49,112	$ 1,470,411	$ 1,279,208	$ (59,073)	$ (53,487)	$ 1,079,801	$ 839,443	$ 2,547,895	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 0.570

Background, Organization, and Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2020

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. Southwest Gas Holdings, Inc. is a holding company, owning all of the shares of common stock of Southwest Gas Corporation (“Southwest” or the “natural gas operations” segment) and all of the shares of common stock of Centuri Group, Inc. (“Centuri,” or the “utility infrastructure services” segment).

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 operations segment are higher during winter periods due to the seasonality incorporated in its regulatory rate structures.

Centuri is a comprehensive utility infrastructure services enterprise dedicated to delivering a diverse array of solutions to North America’s gas and electric providers. Centuri derives revenue from installation, replacement, repair, and maintenance of energy distribution systems, and developing industrial construction solutions. 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”), and Linetec Services, LLC (“Linetec”). Utility infrastructure services activity is seasonal in most of Centuri’s operating areas. Peak periods are the summer and fall months in colder climate areas, such as the northeastern and midwestern United States (“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. The condensed consolidated financial statements of Southwest Gas Holdings, Inc. and subsidiaries (the “Company”) and Southwest included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The year-end condensed balance sheet data was derived from audited financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) have been condensed or omitted pursuant to such rules and regulations. No substantive change has occurred with regard to the Company’s business segments on the whole.

The preparation of the condensed consolidated financial statements 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. In the opinion of management, all adjustments, consisting of normal recurring items and estimates necessary for a fair depiction of results for the interim periods, have been made. Globally, the novel Coronavirus (“COVID-19”) pandemic has created volatility, uncertainty, and economic disruption. Utility operations have been deemed “essential services” and utility infrastructure services have, to a large extent, been similarly characterized by government officials. Management has considered the impact of the pandemic and adjusted certain estimates, where relevant, used in the preparation of the condensed consolidated financial statements.

It is suggested that these condensed consolidated financial statements be read in conjunction with the consolidated financial statements and the notes thereto included in the 2019 Annual Report to Stockholders, which is incorporated by reference into the 2019 Form 10-K.

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 in valuing cash and cash equivalents, derivatives, long-term debt outstanding, and assets of the qualified pension plan and postretirement benefit plans required to be recorded and/or disclosed at fair value.

Other Property and Investments. Other property and investments on the Condensed Consolidated Balance Sheets includes:



(Thousands of dollars)	March 31, 2020			December 31, 2019
Southwest Gas Corporation:
Net cash surrender value of COLI policies	$	116,615		$	132,072
Other property	1,932			1,715
Total Southwest Gas Corporation	118,547			133,787
Centuri property, equipment, and intangibles	1,009,351			983,905
Centuri accumulated provision for depreciation and amortization	(363,074		)	(352,333		)
Other property	20,698			18,814
Total Southwest Gas Holdings, Inc.	$	785,522		$	784,173

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. Balances reflect impacts of equity and fixed-income securities underlying the cash surrender values at each reporting date; however, ultimately, only the insurance proceeds are ever actually received, due to management’s intent to hold the policies to maturity.

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 for Southwest and the Company also include money market fund investments totaling approximately $40,000 and $49,000, respectively, at March 31, 2020, and $23.5 million and $26.7 million, respectively, at December 31, 2019, which 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 Southwest include customer advances applied as contributions toward utility construction activity, capital expenditures that were not paid as of period end reporting dates but rather included in accounts payable, and right-of use assets obtained in exchange for lease liabilities, which are non-cash investing and financing activities. Amounts related to such activities were immaterial for the periods presented herein.

Intercompany Transactions. Centuri recognizes revenues generated from contracts with Southwest (see Note 7 – Segment Information). The accounts receivable balance, revenues, and associated profits are included in the condensed consolidated financial statements of the Company and Southwest and were not eliminated during consolidation in accordance with accounting treatment for rate-regulated entities.

Accounts Receivable, net of allowances. On January 2, 2020, the Company adopted the Financial Accounting Standards Board’s (the “FASB”) Accounting Standards Update (“ASU”) 2016-13 “Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments,” which replaces the incurred loss methodology with an expected loss methodology that is referred to as the current expected credit loss, or CECL, methodology. The Company adopted ASU 2016-13 using the modified retrospective method, and therefore, results for reporting periods beginning prior to January 1, 2020 are presented under previously accepted U.S. GAAP. See Recent Accounting Standards Updates below.

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 no billing due dates customarily extending beyond one month, with customers’ credit worthiness assessed upon account creation by evaluation of other utility service and related payments history. Although Southwest seeks 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, noticing 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 inactivation. 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. Due to the

COVID-19 pandemic, and as utility service is an essential service to the residents in the states in which Southwest operates, Southwest implemented a temporary moratorium on disconnection of natural gas service for non-payment and it also ceased charging late fees until further notice. Southwest is also actively working with customers experiencing financial hardship by means of flexible payment options. Management is monitoring expected credit losses in light of the evolving financial impact of COVID-19, and has adjusted the allowance for uncollectibles as of March 31, 2020 as a result of the anticipated impact on Southwest’s customers’ ability to pay amounts due both currently and when the moratorium is lifted. The adjustment was not material to the financial statements overall, and entering the summer season, during which time monthly billing amounts are substantially reduced, management does not expect a material increase to the allowance for uncollectibles.

Utility infrastructure services contracts 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 trade accounts receivable balances carry standard payment terms of up to 60 days. Centuri maintains an allowance that is an estimate based on historical collection experience, current and forward-looking estimated economic and market conditions, and a review of the current status of each customer's trade 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 as a result of COVID-19 given the nature of its customers.

Activity in the allowance for uncollectibles and the balances as of the periods presented within the Company’s and Southwest’s financial statements are not material to the condensed consolidated financial statements.

Income Taxes. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security (“CARES”) Act was enacted. The CARES Act provides a number of tax provisions and stimulus measures, including changes to prior and future limitations on interest deductions, the ability to accelerate refund of Alternative Minimum Tax credits, elective deferment of payment related to the employer portion of Social Security taxes, and the creation of certain refundable employee retention credits, among other things. Management does not anticipate the impacts, if any, related to the CARES Act to have a material effect on the Company’s or Southwest’s results of operations, financial position, or liquidity.

Prepaid and other current assets. Prepaid and other current assets includes gas pipe materials and operating supplies of $53 million at March 31, 2020 and $57 million at December 31, 2019 (carried at weighted average cost), in addition to $33 million at December 31, 2019 related to a regulatory asset associated with the Arizona decoupling mechanism (an alternative revenue program), with no corresponding asset balance at March 31, 2020.

Goodwill. Goodwill is assessed as of October 1st each year for impairment, or more frequently, if circumstances indicate an impairment to the carrying value of goodwill may have occurred. Management of the Company and Southwest considered its reporting units and segments and determined that its segments and reporting units remain consistent between periods presented below, and that no change was necessary with regard to the level at which goodwill is assessed for impairment. Since December 31, 2019, management also qualitatively assessed whether events during the 1st quarter of 2020 may have resulted in conditions whereby the carrying value of goodwill was higher than its fair value, which if the case, could be an indication of a permanent impairment. Through this assessment, no such condition was believed to have existed and therefore, no impairment was deemed to have occurred in the first three months of 2020.



(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services			Total Company
December 31, 2019	$	10,095	$	332,928		$	343,023
Foreign currency translation adjustment	—		(9,080		)	(9,080		)
March 31, 2020	$	10,095	$	323,848		$	333,943

Other Current Liabilities. Management recognizes in its balance sheets various liabilities that are expected to be settled through future cash payment with the next twelve months, including amounts payable under regulatory mechanisms, customary accrued expenses for employee compensation and benefits, declared but unpaid dividends, and miscellaneous other accrued liabilities. Other current liabilities for Southwest include $25.9 million and $25.2 million of dividends declared by Southwest Gas Corporation, but not yet paid to Southwest Gas Holdings, Inc. as of March 31, 2020 and December 31, 2019, respectively.

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



	Three Months ended March 31,						Twelve Months Ended March 31,
(Thousands of dollars)	2020			2019			2020			2019
Southwest Gas Corporation - natural gas operations segment:
Change in COLI policies	$	(15,500	)	$	7,600		$	(5,700	)	$	5,100
Interest income	1,388			1,597			6,147			6,199
Equity AFUDC	1,061			960			4,262			4,358
Other components of net periodic benefit cost	(5,005		)	(3,765		)	(16,299		)	(19,560		)
Miscellaneous income and (expense)	(2,480		)	(446		)	(5,375		)	(2,788		)
Southwest Gas Corporation - total other income (deductions)	(20,536		)	5,946			(16,965		)	(6,691		)
Utility infrastructure services segment:
Interest income	—			—			—			87
Foreign transaction gain (loss)	(10		)	531			5			162
Miscellaneous income and (expense)	(232		)	344			(656		)	125
Centuri - total other income (deductions)	(242		)	875			(651		)	374
Corporate and administrative	8			18			92			64
Consolidated Southwest Gas Holdings, Inc. - total other income (deductions)	$	(20,770	)	$	6,839		$	(17,524	)	$	(6,253	)

Included in the table above is the change in cash surrender values of 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 values of COLI policies, as they progress towards the ultimate death benefits, are also recorded without tax consequences. Refer to Other Property and Investments above and also to Note 2 – Components of Net Periodic Benefit Cost.

Derivatives. In managing its natural gas supply portfolios, Southwest has historically entered into fixed- and variable-price contracts, which qualify as derivatives. Additionally, Southwest has 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 prices are the prevailing prices at the future transaction dates, the contracts have no determinable fair value. The Swap contract prices are determined at the beginning of each month to reflect that month’s published first of month index price and are recorded at fair value (Level 2). Southwest does not utilize derivative financial instruments for speculative purposes, nor does it have trading operations.

Management does not currently anticipate entering into new Swaps in the near term; the longest maturity date of the Swaps as of March 31, 2020 is October 2020.

Pursuant to regulatory deferral accounting treatment for rate-regulated entities, unrealized gains and losses in fair value of the Swaps are recorded as a regulatory asset and/or liability. When the Swaps mature, any prior positions held are reversed and the settled position is recorded as an increase or decrease of purchased gas under the related purchase gas adjustment (“PGA”) mechanism in determining the deferred PGA balances. Neither changes in fair value nor settled amounts of Swaps have a direct effect on earnings or other comprehensive income, since following settlement, amounts are reflected in Net cost of gas sold at the same time they are included in Gas operating revenues through updates to the PGA component of rates.

Master netting arrangements exist with each counterparty that provide for the net settlement (in the settlement month) of all contracts through a single payment. As applicable, management has elected to reflect the net amounts in its balance sheets, which were immaterial at March 31, 2020. There was no outstanding collateral associated with the Swaps during any period reflected on the Condensed Consolidated Balance Sheets.

Previously, Southwest entered into forward-starting interest rate swaps (“FSIRS”), the settled positions for which are immaterial and continue to be amortized from Accumulated other comprehensive income (loss) into interest expense.

Redeemable Noncontrolling Interest. 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.

Significant changes in the value of the redeemable noncontrolling interest, 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. However, the carrying value was greater than the fair value as of March 31, 2020, and no previous upward redemption value adjustments were made following the acquisition date. SEC guidance indicates that a redemption value adjustment would not be made under these circumstances. The following depicts the change to the balance of the redeemable noncontrolling interest:



(Thousands of dollars):	Redeemable Noncontrolling Interest
Balance, December 31, 2019	$	84,542
Net income attributable to redeemable noncontrolling interest	463
Balance, March 31, 2020	$	85,005

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 the Basic and Diluted EPS calculations is shown in the following table:



	Three Months Ended March 31,		Twelve Months Ended March 31,
(In thousands)	2020	2019	2020	2019
Average basic shares	55,310	53,369	54,726	50,640
Effect of dilutive securities:
Management Incentive Plan shares	—	11	9	22
Restricted stock units (1)	53	44	57	39
Average diluted shares	55,363	53,424	54,792	50,701

(1) The number of securities granted included 50,000 and 40,000 performance shares during the three months ending March 31, 2020 and 2019 and 48,000 and 29,000 performance shares during the twelve months ending March 31, 2020 and 2019, respectively, the total of which was derived by assuming that target performance will be achieved during the relevant performance period.

Recent Accounting Standards Updates.

Accounting pronouncements adopted in 2020:

In June 2016, the FASB issued ASU 2016-13 update “Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” The update requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. The Company and Southwest adopted the update in the first quarter of 2020, and concluded the impact was not material to the condensed consolidated financial statements of the Company or Southwest. See Accounts receivable, net of allowances above.

In January 2017, the FASB issued ASU 2017-04 “Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” Under the update, an entity will apply a one-step quantitative test as opposed to a two-step test as currently required, and record the amount of goodwill impairment as the excess of a reporting unit's carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The new guidance does not amend the optional qualitative assessment. The Company and Southwest adopted the update in the first quarter of 2020 and will apply the update prospectively in any future goodwill impairment tests.

In August 2018, the FASB issued ASU 2018-15 “Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract.” The update generally aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement (that is a service contract) with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software, with the exception that such costs are to be included in the same line item in the balance sheet that a prepayment of the fees associated with the arrangement would be presented. Once capitalized, the update requires the entity to expense the amount capitalized over the term of the hosting arrangement, including reasonably certain renewal periods. The Company and Southwest adopted the update in the first quarter of 2020 using the prospective transition method. There were no material implementation costs related to cloud computing arrangements for the Company and Southwest in the first quarter of 2020.

Recently issued accounting pronouncements that will be effective after 2020:

In August 2018, the FASB issued ASU 2018-14 “Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans.” This update removes disclosures that are no longer considered cost-beneficial, clarifies the specific requirements of disclosures, and adds disclosure requirements identified as relevant. The update applies to all employers that sponsor defined benefit pension or other postretirement plans. The update is effective for fiscal years ending after December 15, 2020. Upon adoption, the Company and Southwest will modify their disclosures to conform to the requirements of the update.

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 update is effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is permitted for periods for which financial statements have not yet been made available for issuance. Management is evaluating the impacts this update might have on the Company’s and Southwest’s consolidated financial statements and disclosures.

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. The update applies only to contracts and hedging relationships that reference LIBOR or another reference rate expected to be discontinued due to reference rate reform. The expedients and exceptions provided by the amendments do not apply to contract modifications made or entered into after December 31, 2022. Management is evaluating the impacts this update might have on the Company’s and Southwest’s consolidated financial statements and disclosures. See also LIBOR discussion in Note 5 – Debt.

Components of Net Periodic Benefit Cost

3 Months Ended

Mar. 31, 2020

Retirement Benefits [Abstract]

Components of Net Periodic Benefit Cost

Note 2 – Components of Net Periodic Benefit Cost

Southwest has a noncontributory qualified retirement plan with defined benefits covering substantially all employees and a separate unfunded supplemental retirement plan (“SERP”) which is limited to officers. Southwest also provides postretirement benefits other than pensions (“PBOP”) to its qualified retirees for health care, dental, and life insurance.

The service cost component of net periodic benefit costs included in the table below are components 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 utility plant, and deferred charges and other assets for both the Company and Southwest. The other components of net periodic benefit cost are reflected in Other income (deductions) on the Condensed Consolidated Statements of Income of each entity.



	Qualified Retirement Plan
	March 31,
	Three Months						Twelve Months
	2020			2019			2020			2019
(Thousands of dollars)
Service cost	$	8,574		$	6,466		$	27,972		$	27,882
Interest cost	11,388			12,252			48,142			45,383
Expected return on plan assets	(16,324		)	(15,061		)	(61,507		)	(59,127		)
Amortization of net actuarial loss	9,007			5,589			25,774			29,675
Net periodic benefit cost	$	12,645		$	9,246		$	40,381		$	43,813

	SERP
	March 31,
	Three Months						Twelve Months
	2020			2019			2020			2019
(Thousands of dollars)
Service cost	$	98		$	66		$	298		$	250
Interest cost	401			440			1,721			1,683
Amortization of net actuarial loss	451			255			1,216			1,382
Net periodic benefit cost	$	950		$	761		$	3,235		$	3,315

	PBOP
	March 31,
	Three Months						Twelve Months
	2020			2019			2020			2019
(Thousands of dollars)
Service cost	$	396		$	319		$	1,353		$	1,424
Interest cost	645			762			2,929			2,823
Expected return on plan assets	(852		)	(789		)	(3,219		)	(3,577		)
Amortization of prior service costs	289			317			1,243			1,318
Net periodic benefit cost	$	478		$	609		$	2,306		$	1,988

Revenue

3 Months Ended

Mar. 31, 2020

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 operations segment and Centuri encompasses the utility infrastructure services segment.

Natural Gas Operations Segment:

Gas operating revenues on the Condensed 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:



	Three Months Ended March 31,						Twelve Months Ended March 31,
(Thousands of dollars)	2020			2019			2020		2019
Residential	$	378,555		$	417,228		$	934,115	$	959,837
Small commercial	82,463			89,610			241,970		256,750
Large commercial	12,667			13,962			47,640		51,714
Industrial/other	6,702			6,478			22,298		23,457
Transportation	24,406			24,902			91,884		87,838
Revenue from contracts with customers	504,793			552,180			1,337,907		1,379,596
Alternative revenue program revenues (deferrals)	(3,765		)	(34,545		)	5,668		(15,775		)
Other revenues	1,799			3,042			7,514		20,271
Total Gas operating revenues	$	502,827		$	520,677		$	1,351,089	$	1,384,092

Utility Infrastructure Services Segment:

The following tables display Centuri’s revenue, reflected as Utility infrastructure services revenues on the Condensed Consolidated Statements of Income of the Company, representing revenue from contracts with customers disaggregated by service and contract types:



	Three Months Ended March 31,				Twelve Months Ended March 31,
(Thousands of dollars)	2020		2019		2020		2019
Service Types:
Gas infrastructure services	$	217,709	$	197,893	$	1,258,790	$	1,128,048
Electric power infrastructure services	72,320		52,301		267,736		79,528
Other	43,464		62,668		245,083		367,554
Total Utility infrastructure services revenues	$	333,493	$	312,862	$	1,771,609	$	1,575,130



	Three Months Ended March 31,				Twelve Months Ended March 31,
(Thousands of dollars)	2020		2019		2020		2019
Contract Types:
Master services agreement	$	263,545	$	235,655	$	1,411,267	$	1,143,603
Bid contract	69,948		77,207		360,342		431,527
Total Utility infrastructure services revenues	$	333,493	$	312,862	$	1,771,609	$	1,575,130

Unit price contracts	$	243,136	$	235,686	$	1,387,706	$	1,296,783
Fixed price contracts	27,545		38,538		101,931		130,295
Time and materials contracts	62,812		38,638		281,972		148,052
Total Utility infrastructure services revenues	$	333,493	$	312,862	$	1,771,609	$	1,575,130

The following table provides information about contracts receivable and revenue earned on contracts in progress in excess of billings (contract asset), which are both included within Accounts receivable, net of allowances, as well as amounts billed in excess of revenue earned on contracts (contract liability), which are included in Other current liabilities as of March 31, 2020 and December 31, 2019 on the Company’s Condensed Consolidated Balance Sheets:



(Thousands of dollars)	March 31, 2020		December 31, 2019
Contracts receivable, net	$	174,228	$	223,904
Revenue earned on contracts in progress in excess of billings	99,967		99,399
Amounts billed in excess of revenue earned on contracts	4,716		4,525

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 for billing at the reporting date. These contract assets are transferred to contracts receivable when the rights become unconditional. 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. The change in this contract liability balance from December 31, 2019 to March 31, 2020 is due to revenue recognized of $4.5 million that was included in this item as of January 1, 2020, after which time it became earned and the balance was reduced, and to increases due to cash received, net of revenue recognized during the period related to contracts that commenced during the period.

For contracts that have an original duration of one year or less, Centuri uses the practical expedient applicable to such contracts and does not consider/compute an interest component based on the time value of money. Further, because of the short duration of these contracts, Centuri 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 March 31, 2020, Centuri had 23 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 March 31, 2020 was $68.2 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 are provided by the customer.

Utility infrastructure services contracts receivable consists of the following:



(Thousands of dollars)	March 31, 2020			December 31, 2019
Billed on completed contracts and contracts in progress	$	169,023		$	216,268
Other receivables	5,644			8,456
Contracts receivable, gross	174,667			224,724
Allowance for doubtful accounts	(439		)	(820		)
Contracts receivable, net	$	174,228		$	223,904

Common Stock

3 Months Ended

Mar. 31, 2020

Equity [Abstract]

Common Stock

Note 4 – Common Stock

Only 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 stock awards to be issued in shares of Southwest Gas Holdings, Inc.

On May 8, 2019, the Company filed with the SEC an automatic shelf registration statement on Form S-3 (File No. 333-231297), which became effective upon filing, for the offer and sale of up to $300 million of common stock from time to time in at-the-market offerings under the prospectus included therein and in accordance with the Sales Agency Agreement, dated May 8, 2019, between the Company and BNY Mellon Capital Markets, LLC (the “Equity Shelf Program”). The Company sold no shares under the Equity Shelf Program during the three months ended March 31, 2020. The following table provides the activity under the Equity Shelf Program for the life-to-date period ended March 31, 2020:



	Life-To-Date Ended
	March 31, 2020
Gross proceeds	$	124,337,247
Less: agent commissions	(1,243,372		)
Net proceeds	$	123,093,875
Number of shares sold	1,478,945
Weighted average price per share	$	84.07

As of March 31, 2020, the Company had up to $175,662,753 of common stock available for sale 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.

During the three months ended March 31, 2020, the Company issued approximately 72,000 shares of common stock through the Restricted Stock/Unit Plan and Management Incentive Plan.

Additionally, during the three months ended March 31, 2020, the Company issued 47,000 shares of common stock through the Dividend Reinvestment and Stock Purchase Plan, raising approximately $3.1 million.

Debt

3 Months Ended

Mar. 31, 2020

Debt Disclosure [Abstract]

Debt

Note 5 – Debt

Long-Term Debt

Long-term debt is recognized in the Company’s and Southwest’s Condensed 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 or provided in the table that follows.

Southwest’s revolving credit facility (including commercial paper) and the variable-rate Industrial Development Revenue Bonds (“IDRBs”) approximate their carrying values. The fair values of the revolving credit facility and IDRBs are categorized as Level 1 based on the FASB’s fair value hierarchy, due to Southwest’s ability to access similar debt arrangements at measurement dates with comparable terms, including variable/market rates. Additionally, the borrowings by Southwest under its revolving credit facility are generally repaid quickly and the IDRBs have interest rates that reset frequently.

The fair values of Southwest’s debentures (which include senior and medium-term notes) were determined utilizing a market-based valuation approach, where fair values are determined based on evaluated pricing data, such as broker quotes and yields for similar securities adjusted for observable differences. Significant inputs used in the valuation generally include benchmark yield curves, credit ratings, and issuer spreads. The external credit rating, coupon rate, and maturity of each security are considered in the valuation, as applicable. The fair values of debentures are categorized as Level 2.

The Centuri secured revolving credit and term loan facility and Centuri’s other debt obligations (not actively traded) are categorized as Level 3. Because Centuri’s debt is not publicly traded, fair values for its secured revolving credit and term loan facility and other debt obligations were based on a conventional discounted cash flow methodology utilizing current market pricing yield curves, across Centuri’s debt maturity spectrum, of other industrial bonds with an assumed credit rating comparable to the Company’s.



	March 31, 2020					December 31, 2019
	Carrying Amount			Market Value		Carrying Amount			Market Value
(Thousands of dollars)
Southwest Gas Corporation:
Debentures:
Notes, 4.45%, due 2020	$	125,000		$	125,975	$	125,000		$	126,673
Notes, 6.1%, due 2041	125,000			178,950		125,000			162,666
Notes, 3.875%, due 2022	250,000			252,688		250,000			258,550
Notes, 4.875%, due 2043	250,000			290,645		250,000			291,928
Notes, 3.8%, due 2046	300,000			278,106		300,000			308,307
Notes, 3.7%, due 2028	300,000			311,565		300,000			320,685
Notes, 4.15%, due 2049	300,000			297,987		300,000			330,138
8% Series, due 2026	75,000			96,435		75,000			96,905
Medium-term notes, 7.78% series, due 2022	25,000			27,293		25,000			27,500
Medium-term notes, 7.92% series, due 2027	25,000			32,621		25,000			32,543
Medium-term notes, 6.76% series, due 2027	7,500			9,185		7,500			9,156
Unamortized discount and debt issuance costs	(14,220		)			(14,450		)
	1,768,280					1,768,050
Revolving credit facility and commercial paper	150,000			150,000		150,000			150,000
Industrial development revenue bonds:
Variable-rate 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	(1,656		)			(1,717		)
	198,344					198,283
Less: current maturities	(125,000		)			(125,000		)
Long-term debt, less current maturities - Southwest Gas Corporation	$	1,991,624				$	1,991,333
Centuri:
Centuri term loan facility	$	232,642		$	228,304	$	244,812		$	252,182
Unamortized debt issuance costs	(1,031		)			(1,101		)
	231,611					243,711
Centuri secured revolving credit facility	42,666			42,658		60,021			60,057
Centuri other debt obligations	88,757			87,758		43,929			44,787
Less: current maturities	(44,574		)			(38,512		)
Long-term debt, less current maturities - Centuri	$	318,460				$	309,149
Consolidated Southwest Gas Holdings, Inc.:
Southwest Gas Corporation long-term debt	$	2,116,624				$	2,116,333
Centuri long-term debt	363,034					347,661
Less: current maturities	(169,574		)			(163,512		)
Long-term debt, less current maturities - Southwest Gas Holdings, Inc.	$	2,310,084				$	2,300,482

Southwest has a $400 million credit facility, for which it has designated $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 London Interbank Offered Rate (“LIBOR”) or an “alternate base rate,” plus in each case an applicable margin that is determined based on Southwest’s senior unsecured debt rating. At March 31, 2020, the applicable margin is 1% for loans bearing interest with reference to LIBOR and 0% for loans bearing interest with reference to the alternative base rate. At March 31, 2020, the full $150 million was outstanding on the long-term portion of the facility.

On April 10, 2020, Southwest amended its credit facility agreement; total borrowing capacity under the amended agreement remains $400 million. The amended agreement extends the maturity date from March 2022 to April 2025. Interest rates for the facility are calculated at either LIBOR or an “alternate base rate,” plus in each case an applicable margin determined based on Southwest’s senior unsecured long-term debt rating. The applicable margin ranges from 0.750% to 1.500% for loans bearing interest with reference to LIBOR and from 0.000% to 0.500% for loans bearing interest with reference to an alternate base rate. Upon the occurrence of certain events providing for a transition away from LIBOR, or if LIBOR is no longer a widely recognized benchmark rate, Southwest may amend the credit facility with a replacement rate as set forth in the amended agreement. 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 ranges from 0.075% to 0.200% per annum. 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 revolving credit facility and, therefore, do not represent additional borrowing capacity under the credit facility. 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 March 31, 2020, no borrowings were outstanding under the commercial paper program.

Centuri has a $590 million senior secured revolving credit and term loan facility, scheduled to expire in November 2023. The capacity of the line of credit portion of the facility is $325 million; amounts borrowed and repaid are available to be re-borrowed. The term loan portion of the facility has a limit of approximately $265 million. The $590 million facility is secured by substantially all of Centuri’s assets except those explicitly excluded under the terms of the agreement (including owned real estate and certain certificated vehicles). Centuri’s assets securing the facility at March 31, 2020 totaled $1.2 billion. At March 31, 2020, $275 million in borrowings were outstanding under the Centuri’s combined secured revolving credit and term loan facility. Centuri also received proceeds of $50 million in equipment loans in 2020, which were used for repayment of outstanding borrowings on the line of credit.

Short-Term Debt

Southwest Gas Holdings, Inc. has a $100 million credit facility that is primarily used for short-term financing needs. There was $60 million outstanding under this credit facility as of March 31, 2020.

On April 10, 2020, Southwest Gas Holdings, Inc. amended its existing credit facility, extending the maturity date to April 2025. The revolving borrowing capacity under the amended agreement remains at $100 million. Interest rates for the amended facility are calculated at either LIBOR or an “alternate base rate,” plus in each case an applicable margin that is determined based on Southwest Gas Holdings, Inc.’s senior unsecured long-term debt rating. The applicable margin ranges from 0.750% to 1.500% for loans bearing interest with reference to LIBOR and from 0.000% to 0.500% for loans bearing interest with reference to the alternate base rate. Upon the occurrence of certain events providing for a transition away from LIBOR, or if LIBOR is no longer a widely recognized benchmark rate, Southwest Gas Holdings, Inc. may amend the credit facility agreement with a replacement rate, as set forth in the amended agreement. Southwest Gas Holdings, Inc. 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 ranges from 0.075% to 0.200% per annum. 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 Gas Holdings, Inc. 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.

As discussed previously, under Southwest’s $400 million credit facility, $250 million has been designated by management for working capital purposes. Southwest had $97 million of short-term borrowings outstanding at March 31, 2020 under this facility.

LIBOR

It is currently anticipated that LIBOR may be discontinued as a benchmark or reference rate after 2021. As of March 31, 2020, $60 million, $247 million, and $177 million, respectively, for the holding company, Southwest, and Centuri was outstanding under their credit facilities whereby interest was with reference to LIBOR and for which maturity dates extend beyond 2021. These amounts reflect approximately 11% of Southwest’s total debt, and 18% of total debt (including current maturities) for the Company overall. Southwest and Southwest Gas Holdings, Inc. (see above) in amending their respective facilities in April 2020 may make further amendments with replacement rates if LIBOR is discontinued. However, replacement rates are not currently determinable. In order to mitigate the impact of a discontinuance on the Company’s and Southwest’s financial condition and results of operations, management will continue to 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 predicable or less attractive than LIBOR.

Other Comprehensive Income and Accumulated Other Comprehensive Income

3 Months Ended

Mar. 31, 2020

Equity [Abstract]

Other Comprehensive Income and Accumulated Other Comprehensive Income

Note 6 – Other Comprehensive Income and Accumulated Other Comprehensive Income

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

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



	Three Months Ended March 31, 2020									Three Months Ended March 31, 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
Defined benefit pension plans:
Amortization of prior service cost	$	289		$	(69	)	$	220		$	317		$	(76	)	$	241
Amortization of net actuarial (gain)/loss	9,458			(2,270		)	7,188			5,844			(1,403		)	4,441
Regulatory adjustment	(8,395		)	2,015			(6,380		)	(5,347		)	1,284			(4,063		)
Pension plans other comprehensive income (loss)	1,352			(324		)	1,028			814			(195		)	619
FSIRS (designated hedging activities):
Amounts reclassified into net income	837			(201		)	636			836			(201		)	635
FSIRS other comprehensive income (loss)	837			(201		)	636			836			(201		)	635
Total other comprehensive income (loss) - Southwest Gas Corporation	2,189			(525		)	1,664			1,650			(396		)	1,254
Foreign currency translation adjustments:
Translation adjustments	(4,005		)	—			(4,005		)	791			—			791
Foreign currency other comprehensive income (loss)	(4,005		)	—			(4,005		)	791			—			791
Total other comprehensive income (loss) - Southwest Gas Holdings, Inc.	$	(1,816	)	$	(525	)	$	(2,341	)	$	2,441		$	(396	)	$	2,045



	Twelve Months Ended March 31, 2020									Twelve Months Ended March 31, 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
Defined benefit pension plans:
Net actuarial gain/(loss)	$	(71,087	)	$	17,061		$	(54,026	)	$	(20,426	)	$	4,902		$	(15,524	)
Amortization of prior service cost	1,243			(298		)	945			1,318			(316		)	1,002
Amortization of net actuarial (gain)/loss	26,990			(6,477		)	20,513			31,057			(7,454		)	23,603
Prior service cost	(1,878		)	452			(1,426		)	—			—			—
Regulatory adjustment	33,896			(8,136		)	25,760			(6,020		)	1,446			(4,574		)
Pension plans other comprehensive income (loss)	(10,836		)	2,602			(8,234		)	5,929			(1,422		)	4,507
FSIRS (designated hedging activities):
Amounts reclassified into net income	3,345			(803		)	2,542			3,344			(803		)	2,541
FSIRS other comprehensive income (loss)	3,345			(803		)	2,542			3,344			(803		)	2,541
Total other comprehensive income (loss) - Southwest Gas Corporation	(7,491		)	1,799			(5,692		)	9,273			(2,225		)	7,048
Foreign currency translation adjustments:
Translation adjustments	(2,758		)	—			(2,758		)	(1,308		)	—			(1,308		)
Foreign currency other comprehensive income (loss)	(2,758		)	—			(2,758		)	(1,308		)	—			(1,308		)
Total other comprehensive income (loss) - Southwest Gas Holdings, Inc.	$	(10,249	)	$	1,799		$	(8,450	)	$	7,965		$	(2,225	)	$	5,740

(1)Tax amounts are calculated using a 24% rate. The Company has elected to indefinitely reinvest the earnings of Centuri’s Canadian subsidiaries in Canada, thus precluding 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 reported in Other comprehensive income (loss).

Approximately $2.2 million of realized losses (net of tax) related to Southwest’s forward-starting interest rate swaps (“FSIRS”), included in AOCI at March 31, 2020, will be reclassified into interest expense within the next 12 months as the related interest payments on long-term debt occur.

The following table represents a rollforward of AOCI, presented on the Company’s Condensed Consolidated Balance Sheets and its Condensed 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, 2019	$	(66,601	)	$	15,985		$	(50,616	)	$	(5,966	)	$	1,431		$	(4,535	)	$	(1,581	)	$	—	$	(1,581	)	$	(56,732	)
Translation adjustments	—			—			—			—			—			—			(4,005		)	—		(4,005		)	(4,005		)
Other comprehensive income (loss) before reclassifications	—			—			—			—			—			—			(4,005		)	—		(4,005		)	(4,005		)
FSIRS amounts reclassified from AOCI (1)	—			—			—			837			(201		)	636			—			—		—			636
Amortization of prior service cost (2)	289			(69		)	220			—			—			—			—			—		—			220
Amortization of net actuarial loss (2)	9,458			(2,270		)	7,188			—			—			—			—			—		—			7,188
Regulatory adjustment (3)	(8,395		)	2,015			(6,380		)	—			—			—			—			—		—			(6,380		)
Net current period other comprehensive income (loss) attributable to Southwest Gas Holdings, Inc.	1,352			(324		)	1,028			837			(201		)	636			(4,005		)	—		(4,005		)	(2,341		)
Ending Balance AOCI March 31, 2020	$	(65,249	)	$	15,661		$	(49,588	)	$	(5,129	)	$	1,230		$	(3,899	)	$	(5,586	)	$	—	$	(5,586	)	$	(59,073	)

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

(2)These AOCI components are included in the computation of net periodic benefit cost (see Note 2 – Components of Net Periodic Benefit Cost 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 Condensed Consolidated Balance Sheets).

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

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



	Defined Benefit Plans									FSIRS
(Thousands of dollars)	Before-Tax			Tax (Expense) Benefit (8)			After-Tax			Before-Tax			Tax (Expense) Benefit (8)			After-Tax			AOCI
Beginning Balance AOCI December 31, 2019	$	(66,601	)	$	15,985		$	(50,616	)	$	(5,966	)	$	1,431		$	(4,535	)	$	(55,151	)
FSIRS amounts reclassified from AOCI (5)	—			—			—			837			(201		)	636			636
Amortization of prior service cost (6)	289			(69		)	220			—			—			—			220
Amortization of net actuarial loss (6)	9,458			(2,270		)	7,188			—			—			—			7,188
Regulatory adjustment (7)	(8,395		)	2,015			(6,380		)	—			—			—			(6,380		)
Net current period other comprehensive income attributable to Southwest Gas Corporation	1,352			(324		)	1,028			837			(201		)	636			1,664
Ending Balance AOCI March 31, 2020	$	(65,249	)	$	15,661		$	(49,588	)	$	(5,129	)	$	1,230		$	(3,899	)	$	(53,487	)

(5) The FSIRS reclassification amounts are included in Net interest deductions on Southwest’s Condensed Consolidated Statements of Income.

(6)These AOCI components are included in the computation of net periodic benefit cost (see Note 2 – Components of Net Periodic Benefit Cost for additional details).

(7)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 Southwest’s Condensed Consolidated Balance Sheets).

(8)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:



(Thousands of dollars)	March 31, 2020			December 31, 2019
Net actuarial (loss) gain	$	(473,616	)	$	(483,074	)
Prior service cost	(3,352		)	(3,641		)
Less: amount recognized in regulatory assets	411,719			420,114
Recognized in AOCI	$	(65,249	)	$	(66,601	)

Segment Information

3 Months Ended

Mar. 31, 2020

Segment Reporting [Abstract]

Segment Information

Note 7 – Segment Information

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:



(Thousands of dollars)	March 31, 2020		December 31, 2019
Centuri accounts receivable for services provided to Southwest	$	16,263	$	15,235

The Company has two reportable segments: natural gas operations and utility infrastructure services. Southwest has a single reportable segment that is referred to herein as the natural gas operations segment of the Company. In order to reconcile to net income as disclosed in the Condensed 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 the natural gas operations and utility infrastructure services segments is as follows:



(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services			Other			Total
Three Months Ended March 31, 2020
Revenues from external customers	$	502,827	$	300,291		$	—		$	803,118
Intersegment revenues	—		33,202			—			33,202
Total	$	502,827	$	333,493		$	—		$	836,320
Segment net income (loss)	$	83,599	$	(10,204	)	$	(853	)	$	72,542

Three Months Ended March 31, 2019
Revenues from external customers	$	520,677	$	274,189		$	—		$	794,866
Intersegment revenues	—		38,673			—			38,673
Total	$	520,677	$	312,862		$	—		$	833,539
Segment net income (loss)	$	103,389	$	(8,031	)	$	(549	)	$	94,809



(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services		Other			Total
Twelve Months Ended March 31, 2020
Revenues from external customers	$	1,351,089	$	1,618,354	$	—		$	2,969,443
Intersegment revenues	—		153,255		—			153,255
Total	$	1,351,089	$	1,771,609	$	—		$	3,122,698
Segment net income (loss)	$	143,381	$	50,231	$	(1,943	)	$	191,669

Twelve Months Ended March 31, 2019
Revenues from external customers	$	1,384,092	$	1,427,701	$	—		$	2,811,793
Intersegment revenues	—		147,429		—			147,429
Total	$	1,384,092	$	1,575,130	$	—		$	2,959,222
Segment net income (loss)	$	151,882	$	47,947	$	(1,834	)	$	197,995

Background, Organization, and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	Nature of Operations. Southwest Gas Holdings, Inc. is a holding company, owning all of the shares of common stock of Southwest Gas Corporation (“Southwest” or the “natural gas operations” segment) and all of the shares of common stock of Centuri Group, Inc. (“Centuri,” or the “utility infrastructure services” segment). 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 operations segment are higher during winter periods due to the seasonality incorporated in its regulatory rate structures. Centuri is a comprehensive utility infrastructure services enterprise dedicated to delivering a diverse array of solutions to North America’s gas and electric providers. Centuri derives revenue from installation, replacement, repair, and maintenance of energy distribution systems, and developing industrial construction solutions. 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”), and Linetec Services, LLC (“Linetec”). Utility infrastructure services activity is seasonal in most of Centuri’s operating areas. Peak periods are the summer and fall months in colder climate areas, such as the northeastern and midwestern United States (“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 condensed consolidated financial statements of Southwest Gas Holdings, Inc. and subsidiaries (the “Company”) and Southwest included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The year-end condensed balance sheet data was derived from audited financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) have been condensed or omitted pursuant to such rules and regulations. No substantive change has occurred with regard to the Company’s business segments on the whole. The preparation of the condensed consolidated financial statements 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. In the opinion of management, all adjustments, consisting of normal recurring items and estimates necessary for a fair depiction of results for the interim periods, have been made. Globally, the novel Coronavirus (“COVID-19”) pandemic has created volatility, uncertainty, and economic disruption. Utility operations have been deemed “essential services” and utility infrastructure services have, to a large extent, been similarly characterized by government officials. Management has considered the impact of the pandemic and adjusted certain estimates, where relevant, used in the preparation of the condensed consolidated financial statements. It is suggested that these condensed consolidated financial statements be read in conjunction with the consolidated financial statements and the notes thereto included in the 2019 Annual Report to Stockholders, which is incorporated by reference into the 2019 Form 10-K.
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 in valuing cash and cash equivalents, derivatives, long-term debt outstanding, and assets of the qualified pension plan and postretirement benefit plans required to be recorded and/or disclosed at fair value.
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 for Southwest and the Company also include money market fund investments totaling approximately $40,000 and $49,000, respectively, at March 31, 2020, and $23.5 million and $26.7 million, respectively, at December 31, 2019, which 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 Southwest include customer advances applied as contributions toward utility construction activity, capital expenditures that were not paid as of period end reporting dates but rather included in accounts payable, and right-of use assets obtained in exchange for lease liabilities, which are non-cash investing and financing activities. Amounts related to such activities were immaterial for the periods presented herein.
Intercompany Transactions	Intercompany Transactions. Centuri recognizes revenues generated from contracts with Southwest (see Note 7 – Segment Information). The accounts receivable balance, revenues, and associated profits are included in the condensed consolidated financial statements of the Company and Southwest and were not eliminated during consolidation in accordance with accounting treatment for rate-regulated entities.
Accounts Receivable, net of allowances	Accounts Receivable, net of allowances. On January 2, 2020, the Company adopted the Financial Accounting Standards Board’s (the “FASB”) Accounting Standards Update (“ASU”) 2016-13 “Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments,” which replaces the incurred loss methodology with an expected loss methodology that is referred to as the current expected credit loss, or CECL, methodology. The Company adopted ASU 2016-13 using the modified retrospective method, and therefore, results for reporting periods beginning prior to January 1, 2020 are presented under previously accepted U.S. GAAP. See Recent Accounting Standards Updates below. 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 no billing due dates customarily extending beyond one month, with customers’ credit worthiness assessed upon account creation by evaluation of other utility service and related payments history. Although Southwest seeks 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, noticing 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 inactivation. 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. Due to the COVID-19 pandemic, and as utility service is an essential service to the residents in the states in which Southwest operates, Southwest implemented a temporary moratorium on disconnection of natural gas service for non-payment and it also ceased charging late fees until further notice. Southwest is also actively working with customers experiencing financial hardship by means of flexible payment options. Management is monitoring expected credit losses in light of the evolving financial impact of COVID-19, and has adjusted the allowance for uncollectibles as of March 31, 2020 as a result of the anticipated impact on Southwest’s customers’ ability to pay amounts due both currently and when the moratorium is lifted. The adjustment was not material to the financial statements overall, and entering the summer season, during which time monthly billing amounts are substantially reduced, management does not expect a material increase to the allowance for uncollectibles. Utility infrastructure services contracts 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 trade accounts receivable balances carry standard payment terms of up to 60 days. Centuri maintains an allowance that is an estimate based on historical collection experience, current and forward-looking estimated economic and market conditions, and a review of the current status of each customer's trade 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 as a result of COVID-19 given the nature of its customers. Activity in the allowance for uncollectibles and the balances as of the periods presented within the Company’s and Southwest’s financial statements are not material to the condensed consolidated financial statements.
Income Taxes	Income Taxes. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security (“CARES”) Act was enacted. The CARES Act provides a number of tax provisions and stimulus measures, including changes to prior and future limitations on interest deductions, the ability to accelerate refund of Alternative Minimum Tax credits, elective deferment of payment related to the employer portion of Social Security taxes, and the creation of certain refundable employee retention credits, among other things. Management does not anticipate the impacts, if any, related to the CARES Act to have a material effect on the Company’s or Southwest’s results of operations, financial position, or liquidity.
Goodwill	Goodwill. Goodwill is assessed as of October 1st each year for impairment, or more frequently, if circumstances indicate an impairment to the carrying value of goodwill may have occurred. Management of the Company and Southwest considered its reporting units and segments and determined that its segments and reporting units remain consistent between periods presented below, and that no change was necessary with regard to the level at which goodwill is assessed for impairment.
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 has 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 prices are the prevailing prices at the future transaction dates, the contracts have no determinable fair value. The Swap contract prices are determined at the beginning of each month to reflect that month’s published first of month index price and are recorded at fair value (Level 2). Southwest does not utilize derivative financial instruments for speculative purposes, nor does it have trading operations.
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.
Recent Accounting Standards Updates	Recent Accounting Standards Updates. Accounting pronouncements adopted in 2020: In June 2016, the FASB issued ASU 2016-13 update “Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” The update requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. The Company and Southwest adopted the update in the first quarter of 2020, and concluded the impact was not material to the condensed consolidated financial statements of the Company or Southwest. See Accounts receivable, net of allowances above. In January 2017, the FASB issued ASU 2017-04 “Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” Under the update, an entity will apply a one-step quantitative test as opposed to a two-step test as currently required, and record the amount of goodwill impairment as the excess of a reporting unit's carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The new guidance does not amend the optional qualitative assessment. The Company and Southwest adopted the update in the first quarter of 2020 and will apply the update prospectively in any future goodwill impairment tests. In August 2018, the FASB issued ASU 2018-15 “Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract.” The update generally aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement (that is a service contract) with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software, with the exception that such costs are to be included in the same line item in the balance sheet that a prepayment of the fees associated with the arrangement would be presented. Once capitalized, the update requires the entity to expense the amount capitalized over the term of the hosting arrangement, including reasonably certain renewal periods. The Company and Southwest adopted the update in the first quarter of 2020 using the prospective transition method. There were no material implementation costs related to cloud computing arrangements for the Company and Southwest in the first quarter of 2020. Recently issued accounting pronouncements that will be effective after 2020: In August 2018, the FASB issued ASU 2018-14 “Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans.” This update removes disclosures that are no longer considered cost-beneficial, clarifies the specific requirements of disclosures, and adds disclosure requirements identified as relevant. The update applies to all employers that sponsor defined benefit pension or other postretirement plans. The update is effective for fiscal years ending after December 15, 2020. Upon adoption, the Company and Southwest will modify their disclosures to conform to the requirements of the update. 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 update is effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is permitted for periods for which financial statements have not yet been made available for issuance. Management is evaluating the impacts this update might have on the Company’s and Southwest’s consolidated financial statements and disclosures. 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. The update applies only to contracts and hedging relationships that reference LIBOR or another reference rate expected to be discontinued due to reference rate reform. The expedients and exceptions provided by the amendments do not apply to contract modifications made or entered into after December 31, 2022. Management is evaluating the impacts this update might have on the Company’s and Southwest’s consolidated financial statements and disclosures. See also LIBOR discussion in Note 5 – Debt.

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

3 Months Ended

Mar. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Other Property and Investments

Other Property and Investments. Other property and investments on the Condensed Consolidated Balance Sheets includes:



(Thousands of dollars)	March 31, 2020			December 31, 2019
Southwest Gas Corporation:
Net cash surrender value of COLI policies	$	116,615		$	132,072
Other property	1,932			1,715
Total Southwest Gas Corporation	118,547			133,787
Centuri property, equipment, and intangibles	1,009,351			983,905
Centuri accumulated provision for depreciation and amortization	(363,074		)	(352,333		)
Other property	20,698			18,814
Total Southwest Gas Holdings, Inc.	$	785,522		$	784,173

Schedule of Goodwill



(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services			Total Company
December 31, 2019	$	10,095	$	332,928		$	343,023
Foreign currency translation adjustment	—		(9,080		)	(9,080		)
March 31, 2020	$	10,095	$	323,848		$	333,943

Other Income (Deductions)

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



	Three Months ended March 31,						Twelve Months Ended March 31,
(Thousands of dollars)	2020			2019			2020			2019
Southwest Gas Corporation - natural gas operations segment:
Change in COLI policies	$	(15,500	)	$	7,600		$	(5,700	)	$	5,100
Interest income	1,388			1,597			6,147			6,199
Equity AFUDC	1,061			960			4,262			4,358
Other components of net periodic benefit cost	(5,005		)	(3,765		)	(16,299		)	(19,560		)
Miscellaneous income and (expense)	(2,480		)	(446		)	(5,375		)	(2,788		)
Southwest Gas Corporation - total other income (deductions)	(20,536		)	5,946			(16,965		)	(6,691		)
Utility infrastructure services segment:
Interest income	—			—			—			87
Foreign transaction gain (loss)	(10		)	531			5			162
Miscellaneous income and (expense)	(232		)	344			(656		)	125
Centuri - total other income (deductions)	(242		)	875			(651		)	374
Corporate and administrative	8			18			92			64
Consolidated Southwest Gas Holdings, Inc. - total other income (deductions)	$	(20,770	)	$	6,839		$	(17,524	)	$	(6,253	)

Summary of Redeemable Noncontrolling Interest

The following depicts the change to the balance of the redeemable noncontrolling interest:



(Thousands of dollars):	Redeemable Noncontrolling Interest
Balance, December 31, 2019	$	84,542
Net income attributable to redeemable noncontrolling interest	463
Balance, March 31, 2020	$	85,005

Schedule of Earnings Per Share, Basic and Diluted

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



	Three Months Ended March 31,		Twelve Months Ended March 31,
(In thousands)	2020	2019	2020	2019
Average basic shares	55,310	53,369	54,726	50,640
Effect of dilutive securities:
Management Incentive Plan shares	—	11	9	22
Restricted stock units (1)	53	44	57	39
Average diluted shares	55,363	53,424	54,792	50,701

Components of Net Periodic Benefit Cost (Tables)

3 Months Ended

Mar. 31, 2020

Retirement Benefits [Abstract]

Schedule of Net Periodic Benefit Costs



	Qualified Retirement Plan
	March 31,
	Three Months						Twelve Months
	2020			2019			2020			2019
(Thousands of dollars)
Service cost	$	8,574		$	6,466		$	27,972		$	27,882
Interest cost	11,388			12,252			48,142			45,383
Expected return on plan assets	(16,324		)	(15,061		)	(61,507		)	(59,127		)
Amortization of net actuarial loss	9,007			5,589			25,774			29,675
Net periodic benefit cost	$	12,645		$	9,246		$	40,381		$	43,813

	SERP
	March 31,
	Three Months						Twelve Months
	2020			2019			2020			2019
(Thousands of dollars)
Service cost	$	98		$	66		$	298		$	250
Interest cost	401			440			1,721			1,683
Amortization of net actuarial loss	451			255			1,216			1,382
Net periodic benefit cost	$	950		$	761		$	3,235		$	3,315

	PBOP
	March 31,
	Three Months						Twelve Months
	2020			2019			2020			2019
(Thousands of dollars)
Service cost	$	396		$	319		$	1,353		$	1,424
Interest cost	645			762			2,929			2,823
Expected return on plan assets	(852		)	(789		)	(3,219		)	(3,577		)
Amortization of prior service costs	289			317			1,243			1,318
Net periodic benefit cost	$	478		$	609		$	2,306		$	1,988

Revenue (Tables)

3 Months Ended

Mar. 31, 2020

Revenue from Contract with Customer [Abstract]

Summary of Revenue Disaggregated by Service Type and Contract Type



	Three Months Ended March 31,						Twelve Months Ended March 31,
(Thousands of dollars)	2020			2019			2020		2019
Residential	$	378,555		$	417,228		$	934,115	$	959,837
Small commercial	82,463			89,610			241,970		256,750
Large commercial	12,667			13,962			47,640		51,714
Industrial/other	6,702			6,478			22,298		23,457
Transportation	24,406			24,902			91,884		87,838
Revenue from contracts with customers	504,793			552,180			1,337,907		1,379,596
Alternative revenue program revenues (deferrals)	(3,765		)	(34,545		)	5,668		(15,775		)
Other revenues	1,799			3,042			7,514		20,271
Total Gas operating revenues	$	502,827		$	520,677		$	1,351,089	$	1,384,092



	Three Months Ended March 31,				Twelve Months Ended March 31,
(Thousands of dollars)	2020		2019		2020		2019
Service Types:
Gas infrastructure services	$	217,709	$	197,893	$	1,258,790	$	1,128,048
Electric power infrastructure services	72,320		52,301		267,736		79,528
Other	43,464		62,668		245,083		367,554
Total Utility infrastructure services revenues	$	333,493	$	312,862	$	1,771,609	$	1,575,130



	Three Months Ended March 31,				Twelve Months Ended March 31,
(Thousands of dollars)	2020		2019		2020		2019
Contract Types:
Master services agreement	$	263,545	$	235,655	$	1,411,267	$	1,143,603
Bid contract	69,948		77,207		360,342		431,527
Total Utility infrastructure services revenues	$	333,493	$	312,862	$	1,771,609	$	1,575,130

Unit price contracts	$	243,136	$	235,686	$	1,387,706	$	1,296,783
Fixed price contracts	27,545		38,538		101,931		130,295
Time and materials contracts	62,812		38,638		281,972		148,052
Total Utility infrastructure services revenues	$	333,493	$	312,862	$	1,771,609	$	1,575,130

Summary of Information about Receivables, Revenue Earned on Contracts in Progress in Excess of Billings, Which are Included Within Accounts Receivable, Net of Allowances, and Amounts Billed in Excess of Revenue Earned on Contracts



(Thousands of dollars)	March 31, 2020		December 31, 2019
Contracts receivable, net	$	174,228	$	223,904
Revenue earned on contracts in progress in excess of billings	99,967		99,399
Amounts billed in excess of revenue earned on contracts	4,716		4,525

Schedule of Construction Services Contracts Receivable

Utility infrastructure services contracts receivable consists of the following:



(Thousands of dollars)	March 31, 2020			December 31, 2019
Billed on completed contracts and contracts in progress	$	169,023		$	216,268
Other receivables	5,644			8,456
Contracts receivable, gross	174,667			224,724
Allowance for doubtful accounts	(439		)	(820		)
Contracts receivable, net	$	174,228		$	223,904

Common Stock (Tables)

3 Months Ended

Mar. 31, 2020

Equity [Abstract]

Schedule of Common Stock Activity

he following table provides the activity under the Equity Shelf Program for the life-to-date period ended March 31, 2020:



	Life-To-Date Ended
	March 31, 2020
Gross proceeds	$	124,337,247
Less: agent commissions	(1,243,372		)
Net proceeds	$	123,093,875
Number of shares sold	1,478,945
Weighted average price per share	$	84.07

Debt (Tables)

3 Months Ended

Mar. 31, 2020

Debt Disclosure [Abstract]

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



	March 31, 2020					December 31, 2019
	Carrying Amount			Market Value		Carrying Amount			Market Value
(Thousands of dollars)
Southwest Gas Corporation:
Debentures:
Notes, 4.45%, due 2020	$	125,000		$	125,975	$	125,000		$	126,673
Notes, 6.1%, due 2041	125,000			178,950		125,000			162,666
Notes, 3.875%, due 2022	250,000			252,688		250,000			258,550
Notes, 4.875%, due 2043	250,000			290,645		250,000			291,928
Notes, 3.8%, due 2046	300,000			278,106		300,000			308,307
Notes, 3.7%, due 2028	300,000			311,565		300,000			320,685
Notes, 4.15%, due 2049	300,000			297,987		300,000			330,138
8% Series, due 2026	75,000			96,435		75,000			96,905
Medium-term notes, 7.78% series, due 2022	25,000			27,293		25,000			27,500
Medium-term notes, 7.92% series, due 2027	25,000			32,621		25,000			32,543
Medium-term notes, 6.76% series, due 2027	7,500			9,185		7,500			9,156
Unamortized discount and debt issuance costs	(14,220		)			(14,450		)
	1,768,280					1,768,050
Revolving credit facility and commercial paper	150,000			150,000		150,000			150,000
Industrial development revenue bonds:
Variable-rate 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	(1,656		)			(1,717		)
	198,344					198,283
Less: current maturities	(125,000		)			(125,000		)
Long-term debt, less current maturities - Southwest Gas Corporation	$	1,991,624				$	1,991,333
Centuri:
Centuri term loan facility	$	232,642		$	228,304	$	244,812		$	252,182
Unamortized debt issuance costs	(1,031		)			(1,101		)
	231,611					243,711
Centuri secured revolving credit facility	42,666			42,658		60,021			60,057
Centuri other debt obligations	88,757			87,758		43,929			44,787
Less: current maturities	(44,574		)			(38,512		)
Long-term debt, less current maturities - Centuri	$	318,460				$	309,149
Consolidated Southwest Gas Holdings, Inc.:
Southwest Gas Corporation long-term debt	$	2,116,624				$	2,116,333
Centuri long-term debt	363,034					347,661
Less: current maturities	(169,574		)			(163,512		)
Long-term debt, less current maturities - Southwest Gas Holdings, Inc.	$	2,310,084				$	2,300,482

- 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.

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+ Details

Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables)

3 Months Ended

Mar. 31, 2020

Equity [Abstract]



	Three Months Ended March 31, 2020									Three Months Ended March 31, 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
Defined benefit pension plans:
Amortization of prior service cost	$	289		$	(69	)	$	220		$	317		$	(76	)	$	241
Amortization of net actuarial (gain)/loss	9,458			(2,270		)	7,188			5,844			(1,403		)	4,441
Regulatory adjustment	(8,395		)	2,015			(6,380		)	(5,347		)	1,284			(4,063		)
Pension plans other comprehensive income (loss)	1,352			(324		)	1,028			814			(195		)	619
FSIRS (designated hedging activities):
Amounts reclassified into net income	837			(201		)	636			836			(201		)	635
FSIRS other comprehensive income (loss)	837			(201		)	636			836			(201		)	635
Total other comprehensive income (loss) - Southwest Gas Corporation	2,189			(525		)	1,664			1,650			(396		)	1,254
Foreign currency translation adjustments:
Translation adjustments	(4,005		)	—			(4,005		)	791			—			791
Foreign currency other comprehensive income (loss)	(4,005		)	—			(4,005		)	791			—			791
Total other comprehensive income (loss) - Southwest Gas Holdings, Inc.	$	(1,816	)	$	(525	)	$	(2,341	)	$	2,441		$	(396	)	$	2,045



	Twelve Months Ended March 31, 2020									Twelve Months Ended March 31, 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
Defined benefit pension plans:
Net actuarial gain/(loss)	$	(71,087	)	$	17,061		$	(54,026	)	$	(20,426	)	$	4,902		$	(15,524	)
Amortization of prior service cost	1,243			(298		)	945			1,318			(316		)	1,002
Amortization of net actuarial (gain)/loss	26,990			(6,477		)	20,513			31,057			(7,454		)	23,603
Prior service cost	(1,878		)	452			(1,426		)	—			—			—
Regulatory adjustment	33,896			(8,136		)	25,760			(6,020		)	1,446			(4,574		)
Pension plans other comprehensive income (loss)	(10,836		)	2,602			(8,234		)	5,929			(1,422		)	4,507
FSIRS (designated hedging activities):
Amounts reclassified into net income	3,345			(803		)	2,542			3,344			(803		)	2,541
FSIRS other comprehensive income (loss)	3,345			(803		)	2,542			3,344			(803		)	2,541
Total other comprehensive income (loss) - Southwest Gas Corporation	(7,491		)	1,799			(5,692		)	9,273			(2,225		)	7,048
Foreign currency translation adjustments:
Translation adjustments	(2,758		)	—			(2,758		)	(1,308		)	—			(1,308		)
Foreign currency other comprehensive income (loss)	(2,758		)	—			(2,758		)	(1,308		)	—			(1,308		)
Total other comprehensive income (loss) - Southwest Gas Holdings, Inc.	$	(10,249	)	$	1,799		$	(8,450	)	$	7,965		$	(2,225	)	$	5,740

Rollforward of Accumulated Other Comprehensive Income

The following table represents a rollforward of AOCI, presented on the Company’s Condensed Consolidated Balance Sheets and its Condensed 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, 2019	$	(66,601	)	$	15,985		$	(50,616	)	$	(5,966	)	$	1,431		$	(4,535	)	$	(1,581	)	$	—	$	(1,581	)	$	(56,732	)
Translation adjustments	—			—			—			—			—			—			(4,005		)	—		(4,005		)	(4,005		)
Other comprehensive income (loss) before reclassifications	—			—			—			—			—			—			(4,005		)	—		(4,005		)	(4,005		)
FSIRS amounts reclassified from AOCI (1)	—			—			—			837			(201		)	636			—			—		—			636
Amortization of prior service cost (2)	289			(69		)	220			—			—			—			—			—		—			220
Amortization of net actuarial loss (2)	9,458			(2,270		)	7,188			—			—			—			—			—		—			7,188
Regulatory adjustment (3)	(8,395		)	2,015			(6,380		)	—			—			—			—			—		—			(6,380		)
Net current period other comprehensive income (loss) attributable to Southwest Gas Holdings, Inc.	1,352			(324		)	1,028			837			(201		)	636			(4,005		)	—		(4,005		)	(2,341		)
Ending Balance AOCI March 31, 2020	$	(65,249	)	$	15,661		$	(49,588	)	$	(5,129	)	$	1,230		$	(3,899	)	$	(5,586	)	$	—	$	(5,586	)	$	(59,073	)

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

(2)These AOCI components are included in the computation of net periodic benefit cost (see Note 2 – Components of Net Periodic Benefit Cost for additional details).

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

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



	Defined Benefit Plans									FSIRS
(Thousands of dollars)	Before-Tax			Tax (Expense) Benefit (8)			After-Tax			Before-Tax			Tax (Expense) Benefit (8)			After-Tax			AOCI
Beginning Balance AOCI December 31, 2019	$	(66,601	)	$	15,985		$	(50,616	)	$	(5,966	)	$	1,431		$	(4,535	)	$	(55,151	)
FSIRS amounts reclassified from AOCI (5)	—			—			—			837			(201		)	636			636
Amortization of prior service cost (6)	289			(69		)	220			—			—			—			220
Amortization of net actuarial loss (6)	9,458			(2,270		)	7,188			—			—			—			7,188
Regulatory adjustment (7)	(8,395		)	2,015			(6,380		)	—			—			—			(6,380		)
Net current period other comprehensive income attributable to Southwest Gas Corporation	1,352			(324		)	1,028			837			(201		)	636			1,664
Ending Balance AOCI March 31, 2020	$	(65,249	)	$	15,661		$	(49,588	)	$	(5,129	)	$	1,230		$	(3,899	)	$	(53,487	)

(5) The FSIRS reclassification amounts are included in Net interest deductions on Southwest’s Condensed Consolidated Statements of Income.

(6)These AOCI components are included in the computation of net periodic benefit cost (see Note 2 – Components of Net Periodic Benefit Cost for additional details).

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

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:



(Thousands of dollars)	March 31, 2020			December 31, 2019
Net actuarial (loss) gain	$	(473,616	)	$	(483,074	)
Prior service cost	(3,352		)	(3,641		)
Less: amount recognized in regulatory assets	411,719			420,114
Recognized in AOCI	$	(65,249	)	$	(66,601	)

Segment Information (Tables)

3 Months Ended

Mar. 31, 2020

Segment Reporting [Abstract]

Accounts Receivable for Services

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



(Thousands of dollars)	March 31, 2020		December 31, 2019
Centuri accounts receivable for services provided to Southwest	$	16,263	$	15,235

Schedule of Segment Reporting Information

The financial information pertaining to the natural gas operations and utility infrastructure services segments is as follows:



(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services			Other			Total
Three Months Ended March 31, 2020
Revenues from external customers	$	502,827	$	300,291		$	—		$	803,118
Intersegment revenues	—		33,202			—			33,202
Total	$	502,827	$	333,493		$	—		$	836,320
Segment net income (loss)	$	83,599	$	(10,204	)	$	(853	)	$	72,542

Three Months Ended March 31, 2019
Revenues from external customers	$	520,677	$	274,189		$	—		$	794,866
Intersegment revenues	—		38,673			—			38,673
Total	$	520,677	$	312,862		$	—		$	833,539
Segment net income (loss)	$	103,389	$	(8,031	)	$	(549	)	$	94,809



(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services		Other			Total
Twelve Months Ended March 31, 2020
Revenues from external customers	$	1,351,089	$	1,618,354	$	—		$	2,969,443
Intersegment revenues	—		153,255		—			153,255
Total	$	1,351,089	$	1,771,609	$	—		$	3,122,698
Segment net income (loss)	$	143,381	$	50,231	$	(1,943	)	$	191,669

Twelve Months Ended March 31, 2019
Revenues from external customers	$	1,384,092	$	1,427,701	$	—		$	2,811,793
Intersegment revenues	—		147,429		—			147,429
Total	$	1,384,092	$	1,575,130	$	—		$	2,959,222
Segment net income (loss)	$	151,882	$	47,947	$	(1,834	)	$	197,995

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Other Property and Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Other property	$ 20,698	$ 18,814
Total	785,522	784,173
Southwest Gas Corporation
Property, Plant and Equipment [Line Items]
Net cash surrender value of COLI policies	116,615	132,072
Other property	1,932	1,715
Total	118,547	133,787
Centuri
Property, Plant and Equipment [Line Items]
Centuri property, equipment, and intangibles	1,009,351	983,905
Centuri accumulated provision for depreciation and amortization	$ (363,074)	$ (352,333)

Background, Organization, and Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2020 USD ($) state	Dec. 31, 2019 USD ($)	Nov. 30, 2018
Significant Accounting Policies [Line Items]
Number of states in which entity operates \| state	3
Threshold period after inactivation for write-off of accounts receivable	2 months
Goodwill impairment	$ 0
Linetec
Significant Accounting Policies [Line Items]
Ownership percentage by noncontrolling owners			20.00%
Gas Pipe Materials and Supplies \| Prepaid and other current assets
Significant Accounting Policies [Line Items]
Gas pipe materials and operating supplies	53,000,000	$ 57,000,000
Prepaid and other current assets	3,000,000	33,000,000
Pooled Funds and Mutual Funds
Significant Accounting Policies [Line Items]
Money market fund investments	49,000	26,700,000
Southwest Gas Corporation
Significant Accounting Policies [Line Items]
Dividends declared but not yet paid	25,900,000	25,200,000
Southwest Gas Corporation \| Pooled Funds and Mutual Funds
Significant Accounting Policies [Line Items]
Money market fund investments	$ 40,000	$ 23,500,000

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 343,023
Foreign currency translation adjustment	(9,080)
Goodwill, ending balance	333,943
Natural Gas Operations
Goodwill [Roll Forward]
Goodwill, beginning balance	10,095
Foreign currency translation adjustment	0
Goodwill, ending balance	10,095
Utility Infrastructure Services
Goodwill [Roll Forward]
Goodwill, beginning balance	332,928
Foreign currency translation adjustment	(9,080)
Goodwill, ending balance	$ 323,848

Background, Organization, and Summary of Significant Accounting Policies - Other Income (Deductions) (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Other income (deductions)
Total other income (deductions)	$ (20,770)	$ 6,839	$ (17,524)	$ (6,253)
Southwest Gas Corporation
Other income (deductions)
Total other income (deductions)	(20,536)	5,946	(16,965)	(6,691)
Operating Segments \| Natural Gas Operations \| Southwest Gas Corporation
Other income (deductions)
Change in COLI policies	(15,500)	7,600	(5,700)	5,100
Interest income	1,388	1,597	6,147	6,199
Equity AFUDC	1,061	960	4,262	4,358
Other components of net periodic benefit cost	(5,005)	(3,765)	(16,299)	(19,560)
Miscellaneous income and (expense)	(2,480)	(446)	(5,375)	(2,788)
Total other income (deductions)	(20,536)	5,946	(16,965)	(6,691)
Operating Segments \| Utility Infrastructure Services \| Centuri
Other income (deductions)
Interest income	0	0	0	87
Foreign transaction gain (loss)	(10)	531	5	162
Miscellaneous income and (expense)	(232)	344	(656)	125
Total other income (deductions)	(242)	875	(651)	374
Corporate and administrative
Other income (deductions)
Total other income (deductions)	$ 8	$ 18	$ 92	$ 64

Background, Organization, and Summary of Significant Accounting Policies - Summary of Redeemable Noncontrolling Interest (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Movement In Redeemable Noncontrolling Interest [Roll Forward]
Balance, December 31, 2019	$ 84,542
Net income attributable to redeemable noncontrolling interest	463
Balance, March 31, 2020	$ 85,005

Background, Organization, and Summary of Significant Accounting Policies Background, Organization, and Summary of Significant Accounting Policies - Schedule of Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Average basic shares (in shares)	55,310	53,369	54,726	50,640
Effect of dilutive securities:
Management Incentive Plan shares (in shares)	0	11	9	22
Restricted stock units (in shares)	53	44	57	39
Average diluted shares (in shares)	55,363	53,424	54,792	50,701
Number of performance share units granted (in shares)	50	40	48	29

Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Qualified Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,574	$ 6,466	$ 27,972	$ 27,882
Interest cost	11,388	12,252	48,142	45,383
Expected return on plan assets	(16,324)	(15,061)	(61,507)	(59,127)
Amortization of net actuarial loss	9,007	5,589	25,774	29,675
Net periodic benefit cost	12,645	9,246	40,381	43,813
SERP
Defined Benefit Plan Disclosure [Line Items]
Service cost	98	66	298	250
Interest cost	401	440	1,721	1,683
Amortization of net actuarial loss	451	255	1,216	1,382
Net periodic benefit cost	950	761	3,235	3,315
PBOP
Defined Benefit Plan Disclosure [Line Items]
Service cost	396	319	1,353	1,424
Interest cost	645	762	2,929	2,823
Expected return on plan assets	(852)	(789)	(3,219)	(3,577)
Amortization of prior service costs	289	317	1,243	1,318
Net periodic benefit cost	$ 478	$ 609	$ 2,306	$ 1,988

Revenue - Additional Information (Detail) $ in Millions	3 Months Ended
Revenue - Additional Information (Detail) $ in Millions	Mar. 31, 2020 USD ($) Contract
Segment Reporting Information [Line Items]
Change in contract liability, revenue recognized \| $	$ 4.5
Centuri
Segment Reporting Information [Line Items]
Number of contracts with original duration more than one year \| Contract	23

Revenue - Revenue Performance Obligation (Details) - Centuri - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01 $ in Millions	Mar. 31, 2020 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction price allocated to unsatisfied performance obligations of contracts	$ 68.2
Revenue, remaining performance obligation, expected timing of satisfaction, period	2 years

Revenue - Schedule of Gas Operating Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 504,793	$ 552,180	$ 1,337,907	$ 1,379,596
Alternative revenue program revenues (deferrals)	(3,765)	(34,545)	5,668	(15,775)
Other revenues	1,799	3,042	7,514	20,271
Total Gas operating revenues	502,827	520,677	1,351,089	1,384,092
Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	378,555	417,228	934,115	959,837
Small commercial
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	82,463	89,610	241,970	256,750
Large commercial
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12,667	13,962	47,640	51,714
Industrial/other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6,702	6,478	22,298	23,457
Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 24,406	$ 24,902	$ 91,884	$ 87,838

Revenue - Summary of Revenue Disaggregated by Service Type, and Contract Type (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 504,793	$ 552,180	$ 1,337,907	$ 1,379,596
Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	333,493	312,862	1,771,609	1,575,130
Master services agreement \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	263,545	235,655	1,411,267	1,143,603
Bid contract \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	69,948	77,207	360,342	431,527
Unit price contracts \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	243,136	235,686	1,387,706	1,296,783
Fixed price contracts \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	27,545	38,538	101,931	130,295
Time and materials contracts \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	62,812	38,638	281,972	148,052
Gas infrastructure services \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	217,709	197,893	1,258,790	1,128,048
Electric power infrastructure services \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	72,320	52,301	267,736	79,528
Other \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 43,464	$ 62,668	$ 245,083	$ 367,554

Revenue - Summary of Information about Receivables (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Contracts receivable, net	$ 174,228	$ 223,904
Revenue earned on contracts in progress in excess of billings	99,967	99,399
Amounts billed in excess of revenue earned on contracts	$ 4,716	$ 4,525

Revenue - Schedule of Construction Services Contracts Receivable (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Billed on completed contracts and contracts in progress	$ 169,023	$ 216,268
Other receivables	5,644	8,456
Contracts receivable, gross	174,667	224,724
Allowance for doubtful accounts	(439)	(820)
Contracts receivable, net	$ 174,228	$ 223,904

Common Stock (Detail) - USD ($)	3 Months Ended		11 Months Ended	12 Months Ended
Common Stock (Detail) - USD ($)	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2020	Mar. 31, 2019	May 08, 2019
Class of Stock [Line Items]
Net proceeds to company	$ 3,148,000	$ 25,879,000		$ 135,215,000	$ 369,061,000
Restricted Stock/Unit Plan, and Management Incentive Plan
Class of Stock [Line Items]
Common stock issued (in shares)	72,000
Dividend Reinvestment and Stock Purchase Plan
Class of Stock [Line Items]
Common stock issued (in shares)	47,000
Common stock issued, amount	$ 3,100,000
Equity Shelf Program
Class of Stock [Line Items]
Sale of stock, maximum amount of stock allowed to be offered						300,000,000
Gross proceeds			$ 124,337,247
Agent commissions			(1,243,372)
Net proceeds to company			$ 123,093,875
Number of shares sold (in shares)			1,478,945
Weighted average price per share			$ 84.07
Sale of stock, common stock available for sale	$ 175,662,753		$ 175,662,753	$ 175,662,753

Debt - Schedule of Long-Term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Less: current maturities	$ (169,574)	$ (163,512)
Long-term debt, less current maturities	2,310,084	2,300,482
Long-term Debt, Current and Noncurrent Abstract
Less: current maturities	(169,574)	(163,512)
Long-term debt, less current maturities	2,310,084	2,300,482
Southwest Gas Corporation
Debt Instrument [Line Items]
Less: current maturities	(125,000)	(125,000)
Long-term debt, less current maturities	1,991,624	1,991,333
Long-term Debt, Current and Noncurrent Abstract
Less: current maturities	(125,000)	(125,000)
Long-term debt, less current maturities	$ 1,991,624	1,991,333
Debentures \| Notes, 4.45%, due 2020 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	4.45%
Debentures \| Notes, 6.1%, due 2041 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	6.10%
Debentures \| Notes, 3.875%, due 2022 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	3.875%
Debentures \| Notes, 4.875%, due 2043 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	4.875%
Debentures \| Notes, 3.8%, due 2046 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	3.80%
Debentures \| Notes, 3.7%, due 2028 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	3.70%
Debentures \| Notes, 4.15%, due 2049 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	4.15%
Debentures \| 8% Series, due 2026 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	8.00%
Debentures \| Medium-term notes, 7.78% series, due 2022 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	7.78%
Debentures \| Medium-term notes, 7.92% series, due 2027 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	7.92%
Debentures \| Medium-term notes, 6.76% series, due 2027 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	6.76%
Carrying Amount
Debt Instrument [Line Items]
Less: current maturities	$ (169,574)	(163,512)
Long-term debt, less current maturities	2,310,084	2,300,482
Long-term Debt, Current and Noncurrent Abstract
Less: current maturities	(169,574)	(163,512)
Long-term debt, less current maturities	2,310,084	2,300,482
Carrying Amount \| Southwest Gas Corporation
Debt Instrument [Line Items]
Less: current maturities	(125,000)	(125,000)
Long-term debt, less current maturities	1,991,624	1,991,333
Long-term Debt, Current and Noncurrent Abstract
Long-term debt	2,116,624	2,116,333
Less: current maturities	(125,000)	(125,000)
Long-term debt, less current maturities	1,991,624	1,991,333
Carrying Amount \| Centuri
Debt Instrument [Line Items]
Less: current maturities	(44,574)	(38,512)
Long-term debt, less current maturities	318,460	309,149
Unamortized debt issuance costs	(1,031)	(1,101)
Long-term Debt, Current and Noncurrent Abstract
Long-term debt	363,034	347,661
Less: current maturities	(44,574)	(38,512)
Long-term debt, less current maturities	318,460	309,149
Centuri secured revolving credit facility	231,611	243,711
Carrying Amount \| Centuri secured revolving credit facility \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri secured revolving credit facility	42,666	60,021
Carrying Amount \| Centuri term loan facility \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri secured revolving credit facility	232,642	244,812
Carrying Amount \| Centuri other debt obligations \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri other debt obligations	88,757	43,929
Carrying Amount \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	1,768,280	1,768,050
Unamortized discount and debt issuance costs	(14,220)	(14,450)
Carrying Amount \| Debentures \| Notes, 4.45%, due 2020 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	125,000	125,000
Carrying Amount \| Debentures \| Notes, 6.1%, due 2041 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	125,000	125,000
Carrying Amount \| Debentures \| Notes, 3.875%, due 2022 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	250,000	250,000
Carrying Amount \| Debentures \| Notes, 4.875%, due 2043 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	250,000	250,000
Carrying Amount \| Debentures \| Notes, 3.8%, due 2046 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	300,000	300,000
Carrying Amount \| Debentures \| Notes, 3.7%, due 2028 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	300,000	300,000
Carrying Amount \| Debentures \| Notes, 4.15%, due 2049 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	300,000	300,000
Carrying Amount \| Debentures \| 8% Series, due 2026 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	75,000	75,000
Carrying Amount \| Debentures \| Medium-term notes, 7.78% series, due 2022 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	25,000	25,000
Carrying Amount \| Debentures \| Medium-term notes, 7.92% series, due 2027 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	25,000	25,000
Carrying Amount \| Debentures \| Medium-term notes, 6.76% series, due 2027 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	7,500	7,500
Carrying Amount \| Debentures \| Revolving credit facility and commercial paper \| Southwest Gas Corporation
Debt Instrument [Line Items]
Line of credit facility	150,000	150,000
Carrying Amount \| Industrial development revenue bonds \| Southwest Gas Corporation
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(1,656)	(1,717)
Unsecured debt	198,344	198,283
Carrying Amount \| Industrial development revenue bonds \| Tax-exempt Series A, due 2028 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Unsecured debt	50,000	50,000
Carrying Amount \| Industrial development revenue bonds \| 2003 Series A, due 2038 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Unsecured debt	50,000	50,000
Carrying Amount \| Industrial development revenue bonds \| 2008 Series A, due 2038 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Unsecured debt	50,000	50,000
Carrying Amount \| Industrial development revenue bonds \| 2009 Series A, due 2039 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Unsecured debt	50,000	50,000
Market Value \| Centuri secured revolving credit facility \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri secured revolving credit facility	42,658	60,057
Market Value \| Centuri term loan facility \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri secured revolving credit facility	228,304	252,182
Market Value \| Centuri other debt obligations \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri other debt obligations	87,758	44,787
Market Value \| Debentures \| Notes, 4.45%, due 2020 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	125,975	126,673
Market Value \| Debentures \| Notes, 6.1%, due 2041 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	178,950	162,666
Market Value \| Debentures \| Notes, 3.875%, due 2022 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	252,688	258,550
Market Value \| Debentures \| Notes, 4.875%, due 2043 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	290,645	291,928
Market Value \| Debentures \| Notes, 3.8%, due 2046 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	278,106	308,307
Market Value \| Debentures \| Notes, 3.7%, due 2028 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	311,565	320,685
Market Value \| Debentures \| Notes, 4.15%, due 2049 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	297,987	330,138
Market Value \| Debentures \| 8% Series, due 2026 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	96,435	96,905
Market Value \| Debentures \| Medium-term notes, 7.78% series, due 2022 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	27,293	27,500
Market Value \| Debentures \| Medium-term notes, 7.92% series, due 2027 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	32,621	32,543
Market Value \| Debentures \| Medium-term notes, 6.76% series, due 2027 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	9,185	9,156
Market Value \| Debentures \| Revolving credit facility and commercial paper \| Southwest Gas Corporation
Debt Instrument [Line Items]
Line of credit facility, fair value	150,000	150,000
Market Value \| Industrial development revenue bonds \| Tax-exempt Series A, due 2028 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Unsecured debt	50,000	50,000
Market Value \| Industrial development revenue bonds \| 2003 Series A, due 2038 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Unsecured debt	50,000	50,000
Market Value \| Industrial development revenue bonds \| 2008 Series A, due 2038 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Unsecured debt, fair value	50,000	50,000
Market Value \| Industrial development revenue bonds \| 2009 Series A, due 2039 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Unsecured debt, fair value	$ 50,000	$ 50,000

Debt - Additional Information (Detail)		3 Months Ended
Debt - Additional Information (Detail)	Apr. 10, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Nov. 30, 2018 USD ($)	Mar. 31, 2017 USD ($)
Debt Instrument [Line Items]
Short term borrowings outstanding		$ 157,000,000	$ 211,000,000
Percentage of total debt with interest rates reference to LIBOR and due after 2021		18.00%
Southwest Gas Corporation
Debt Instrument [Line Items]
Short term borrowings outstanding		$ 97,000,000	$ 194,000,000
Percentage of total debt with interest rates reference to LIBOR and due after 2021		11.00%
LIBOR \| Southwest Gas Corporation
Debt Instrument [Line Items]
Borrowings outstanding under facility		$ 247,000,000
LIBOR \| Centuri
Debt Instrument [Line Items]
Borrowings outstanding under facility		177,000,000
Commercial Paper Program \| Southwest Gas Corporation
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity		50,000,000
Borrowings outstanding under facility		0
Secured Revolving Credit Facility and Term Loan \| Centuri
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity				$ 590,000,000
Borrowings outstanding under facility		275,000,000
Debt secured by assets		1,200,000,000
Line of Credit \| Centuri
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity				325,000,000
Centuri term loan facility \| Centuri
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity				$ 265,000,000
Equipment Loans \| Centuri
Debt Instrument [Line Items]
Proceeds from debt		50,000,000
$400 Million Credit Facility \| Southwest Gas Corporation
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity		400,000,000
Line of credit designated as long term debt		150,000,000
Line of credit designated for working capital purposes		250,000,000
Long-term debt		150,000,000
Short term borrowings outstanding		$ 97,000,000
$400 Million Credit Facility \| LIBOR \| Southwest Gas Corporation
Debt Instrument [Line Items]
Applicable margin		1.00%
$400 Million Credit Facility \| Alternative base rate \| Southwest Gas Corporation
Debt Instrument [Line Items]
Applicable margin		0.00%
$100 Million Credit Facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity					$ 100,000,000
Short term borrowings outstanding		$ 60,000,000
Subsequent Event \| $400 Million Credit Facility \| Southwest Gas Corporation
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity	$ 400,000,000
Debt covenant, ratio of funded debt to total capitalization	0.70
Subsequent Event \| $100 Million Credit Facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity	$ 100,000,000
Debt covenant, ratio of funded debt to total capitalization	0.70
Subsequent Event \| Minimum \| $400 Million Credit Facility
Debt Instrument [Line Items]
Commitment fee percentage	0.075%
Subsequent Event \| Minimum \| $400 Million Credit Facility \| LIBOR
Debt Instrument [Line Items]
Applicable margin	0.75%
Subsequent Event \| Minimum \| $400 Million Credit Facility \| Alternative base rate
Debt Instrument [Line Items]
Applicable margin	0.00%
Subsequent Event \| Minimum \| $100 Million Credit Facility
Debt Instrument [Line Items]
Commitment fee percentage	0.075%
Subsequent Event \| Minimum \| $100 Million Credit Facility \| LIBOR
Debt Instrument [Line Items]
Applicable margin	0.75%
Subsequent Event \| Minimum \| $100 Million Credit Facility \| Alternative base rate
Debt Instrument [Line Items]
Applicable margin	0.00%
Subsequent Event \| Maximum \| $400 Million Credit Facility
Debt Instrument [Line Items]
Commitment fee percentage	0.20%
Subsequent Event \| Maximum \| $400 Million Credit Facility \| LIBOR
Debt Instrument [Line Items]
Applicable margin	1.50%
Subsequent Event \| Maximum \| $400 Million Credit Facility \| Alternative base rate
Debt Instrument [Line Items]
Applicable margin	0.50%
Subsequent Event \| Maximum \| $100 Million Credit Facility
Debt Instrument [Line Items]
Commitment fee percentage	0.20%
Subsequent Event \| Maximum \| $100 Million Credit Facility \| LIBOR
Debt Instrument [Line Items]
Applicable margin	1.50%
Subsequent Event \| Maximum \| $100 Million Credit Facility \| Alternative base rate
Debt Instrument [Line Items]
Applicable margin	0.50%

Other Comprehensive Income and Accumulated Other Comprehensive Income - Related Tax Effects Allocated to OCI (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, net of tax	$ (4,005)
Other comprehensive income (loss), before tax	(1,816)	$ 2,441	$ (10,249)	$ 7,965
Other comprehensive income (loss), tax	(525)	(396)	1,799	(2,225)
Total other comprehensive income (loss), net of tax	$ (2,341)	2,045	$ (8,450)	5,740
Effective income tax rate	24.00%		24.00%
Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ 2,189	1,650	$ (7,491)	9,273
Other comprehensive income (loss), tax	(525)	(396)	1,799	(2,225)
Total other comprehensive income (loss), net of tax	1,664	1,254	(5,692)	7,048
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	1,352	814	(10,836)	5,929
Other comprehensive income (loss), tax	(324)	(195)	2,602	(1,422)
Total other comprehensive income (loss), net of tax	1,028	619	(8,234)	4,507
Defined Benefit Plans \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	1,352
Other comprehensive income (loss), tax	(324)
Total other comprehensive income (loss), net of tax	1,028
Amortization of prior service cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	289	317	1,243	1,318
Reclassification from AOCI, tax	(69)	(76)	(298)	(316)
Reclassification from AOCI, net of tax	220	241	945	1,002
Other comprehensive income (loss), before tax	289
Other comprehensive income (loss), tax	(69)
Total other comprehensive income (loss), net of tax	220
Amortization of prior service cost \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	289
Other comprehensive income (loss), tax	(69)
Total other comprehensive income (loss), net of tax	220
Net actuarial gain/(loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax			(71,087)	(20,426)
Other comprehensive income (loss) before reclassifications, tax			17,061	4,902
Other comprehensive income (loss) before reclassifications, net of tax			(54,026)	(15,524)
Reclassification from AOCI, before Tax	9,458	5,844	26,990	31,057
Reclassification from AOCI, tax	(2,270)	(1,403)	(6,477)	(7,454)
Reclassification from AOCI, net of tax	7,188	4,441	20,513	23,603
Other comprehensive income (loss), before tax	9,458
Other comprehensive income (loss), tax	(2,270)
Total other comprehensive income (loss), net of tax	7,188
Net actuarial gain/(loss) \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	9,458
Other comprehensive income (loss), tax	(2,270)
Total other comprehensive income (loss), net of tax	7,188
Prior service cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax			(1,878)	0
Other comprehensive income (loss) before reclassifications, tax			452	0
Other comprehensive income (loss) before reclassifications, net of tax			(1,426)	0
Regulatory adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	(8,395)	(5,347)	33,896	(6,020)
Reclassification from AOCI, tax	2,015	1,284	(8,136)	1,446
Reclassification from AOCI, net of tax	(6,380)	(4,063)	25,760	(4,574)
Other comprehensive income (loss), before tax	(8,395)
Other comprehensive income (loss), tax	2,015
Total other comprehensive income (loss), net of tax	(6,380)
Regulatory adjustment \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	(8,395)
Other comprehensive income (loss), tax	2,015
Total other comprehensive income (loss), net of tax	(6,380)
FSIRS
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	837	836	3,345	3,344
Reclassification from AOCI, tax	(201)	(201)	(803)	(803)
Reclassification from AOCI, net of tax	636	635	2,542	2,541
Other comprehensive income (loss), before tax	837	836	3,345	3,344
Other comprehensive income (loss), tax	(201)	(201)	(803)	(803)
Total other comprehensive income (loss), net of tax	636	635	2,542	2,541
FSIRS \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	837
Reclassification from AOCI, tax	(201)
Reclassification from AOCI, net of tax	636
Other comprehensive income (loss), before tax	837
Other comprehensive income (loss), tax	(201)
Total other comprehensive income (loss), net of tax	636
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax	(4,005)	791	(2,758)	(1,308)
Other comprehensive income (loss) before reclassifications, tax	0	0	0	0
Other comprehensive income (loss) before reclassifications, net of tax	(4,005)	$ 791	$ (2,758)	$ (1,308)
Other comprehensive income (loss), before tax	(4,005)
Total other comprehensive income (loss), net of tax	$ (4,005)

Other Comprehensive Income and Accumulated Other Comprehensive Income - Additional Information (Detail) $ in Millions	Mar. 31, 2020 USD ($)
Equity [Abstract]
Amount of FSIRS existing AOCI losses expected to reclassified income in next twelve months	$ 2.2

Other Comprehensive Income and Accumulated Other Comprehensive Income - AOCI Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ 2,346,548
Beginning balance, attributable to parent	$ 2,505,914
Other comprehensive income (loss) before reclassifications, net of tax	(4,005)
Other comprehensive income (loss), before tax	(1,816)	$ 2,441	(10,249)	$ 7,965
Other comprehensive income (loss), tax	(525)	(396)	1,799	(2,225)
Total other comprehensive income (loss), net of tax	(2,341)	2,045	(8,450)	5,740
Ending balance, attributable to parent	2,547,895		2,547,895
Ending balance	$ 2,547,895	2,346,548	$ 2,547,895	2,346,548
Effective income tax rate	24.00%		24.00%
Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, before tax	$ (66,601)
Beginning balance, tax	15,985
Beginning balance	(50,616)
Other comprehensive income (loss), before tax	1,352	814	$ (10,836)	5,929
Other comprehensive income (loss), tax	(324)	(195)	2,602	(1,422)
Total other comprehensive income (loss), net of tax	1,028	619	(8,234)	4,507
Ending balance, before tax	(65,249)		(65,249)
Ending balance, tax	15,661		15,661
Ending balance	(49,588)		(49,588)
Amortization of prior service cost
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, before Tax	289	317	1,243	1,318
Reclassification from AOCI, tax	(69)	(76)	(298)	(316)
Reclassification from AOCI, net of tax	220	241	945	1,002
Other comprehensive income (loss), before tax	289
Other comprehensive income (loss), tax	(69)
Total other comprehensive income (loss), net of tax	220
Amortization of net actuarial loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications, before tax			(71,087)	(20,426)
Other comprehensive income (loss) before reclassifications, net of tax			(54,026)	(15,524)
Reclassification from AOCI, before Tax	9,458	5,844	26,990	31,057
Reclassification from AOCI, tax	(2,270)	(1,403)	(6,477)	(7,454)
Reclassification from AOCI, net of tax	7,188	4,441	20,513	23,603
Other comprehensive income (loss), before tax	9,458
Other comprehensive income (loss), tax	(2,270)
Total other comprehensive income (loss), net of tax	7,188
Regulatory adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, before Tax	(8,395)	(5,347)	33,896	(6,020)
Reclassification from AOCI, tax	2,015	1,284	(8,136)	1,446
Reclassification from AOCI, net of tax	(6,380)	(4,063)	25,760	(4,574)
Other comprehensive income (loss), before tax	(8,395)
Other comprehensive income (loss), tax	2,015
Total other comprehensive income (loss), net of tax	(6,380)
FSIRS
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, before tax	(5,966)
Beginning balance, tax	1,431
Beginning balance	(4,535)
Reclassification from AOCI, before Tax	837	836	3,345	3,344
Reclassification from AOCI, tax	(201)	(201)	(803)	(803)
Reclassification from AOCI, net of tax	636	635	2,542	2,541
Other comprehensive income (loss), before tax	837	836	3,345	3,344
Other comprehensive income (loss), tax	(201)	(201)	(803)	(803)
Total other comprehensive income (loss), net of tax	636	635	2,542	2,541
Ending balance, before tax	(5,129)		(5,129)
Ending balance, tax	1,230		1,230
Ending balance	(3,899)		(3,899)
Foreign Currency Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, before tax	(1,581)
Beginning balance	(1,581)
Other comprehensive income (loss) before reclassifications, before tax	(4,005)	791	(2,758)	(1,308)
Other comprehensive income (loss) before reclassifications, net of tax	(4,005)	791	(2,758)	(1,308)
Other comprehensive income (loss), before tax	(4,005)
Total other comprehensive income (loss), net of tax	(4,005)
Ending balance, before tax	(5,586)		(5,586)
Ending balance	(5,586)		(5,586)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(56,732)	(52,668)	(50,623)
Ending balance	(59,073)	(50,623)	(59,073)	(50,623)
Southwest Gas Corporation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			1,887,903
Beginning balance, attributable to parent	2,005,152
Other comprehensive income (loss), before tax	2,189	1,650	(7,491)	9,273
Other comprehensive income (loss), tax	(525)	(396)	1,799	(2,225)
Total other comprehensive income (loss), net of tax	1,664	1,254	(5,692)	7,048
Ending balance, attributable to parent	2,114,276		2,114,276
Ending balance	2,114,276	1,887,903	2,114,276	1,887,903
Southwest Gas Corporation \| Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, attributable to parent, before tax	(66,601)
Beginning balance, attributable to parent, tax	15,985
Beginning balance, attributable to parent	(50,616)
Other comprehensive income (loss), before tax	1,352
Other comprehensive income (loss), tax	(324)
Total other comprehensive income (loss), net of tax	1,028
Ending balance, attributable to parent, before tax	(65,249)		(65,249)
Ending balance, attributable to parent, tax	15,661		15,661
Ending balance, attributable to parent	(49,588)		(49,588)
Southwest Gas Corporation \| Amortization of prior service cost
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before tax	289
Other comprehensive income (loss), tax	(69)
Total other comprehensive income (loss), net of tax	220
Southwest Gas Corporation \| Amortization of net actuarial loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before tax	9,458
Other comprehensive income (loss), tax	(2,270)
Total other comprehensive income (loss), net of tax	7,188
Southwest Gas Corporation \| Regulatory adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before tax	(8,395)
Other comprehensive income (loss), tax	2,015
Total other comprehensive income (loss), net of tax	(6,380)
Southwest Gas Corporation \| FSIRS
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, attributable to parent, before tax	(5,966)
Beginning balance, attributable to parent, tax	1,431
Beginning balance, attributable to parent	(4,535)
Reclassification from AOCI, before Tax	837
Reclassification from AOCI, tax	(201)
Reclassification from AOCI, net of tax	636
Other comprehensive income (loss), before tax	837
Other comprehensive income (loss), tax	(201)
Total other comprehensive income (loss), net of tax	636
Ending balance, attributable to parent, before tax	(5,129)		(5,129)
Ending balance, attributable to parent, tax	1,230		1,230
Ending balance, attributable to parent	(3,899)		(3,899)
Southwest Gas Corporation \| AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(55,151)	(49,049)	(47,795)
Beginning balance, attributable to parent	(55,151)
Ending balance, attributable to parent	(53,487)		(53,487)
Ending balance	$ (53,487)	$ (47,795)	$ (53,487)	$ (47,795)

Other Comprehensive Income and Accumulated Other Comprehensive Income - Amounts Recognized Before Tax, Defined Benefit Plans (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Equity [Abstract]
Net actuarial (loss) gain	$ (473,616)	$ (483,074)
Prior service cost	(3,352)	(3,641)
Less: amount recognized in regulatory assets	411,719	420,114
Recognized in AOCI	$ (65,249)	$ (66,601)

Segment Information - Accounts Receivable for Services (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Centuri
Segment Reporting Information [Line Items]
Centuri accounts receivable for services provided to Southwest	$ 16,263	$ 15,235

Segment Information - Additional Information (Detail)	3 Months Ended
Segment Information - Additional Information (Detail)	Mar. 31, 2020 Segment
Segment Reporting [Abstract]
Number of reportable segments	2

Segment Information - Schedule of Reporting Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 836,320	$ 833,539	$ 3,122,698	$ 2,959,222
Segment net income (loss)	72,542	94,809	191,669	197,995
Operating Segments
Segment Reporting Information [Line Items]
Revenues	803,118	794,866	2,969,443	2,811,793
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	33,202	38,673	153,255	147,429
Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Segment net income (loss)	(853)	(549)	(1,943)	(1,834)
Natural Gas Operations
Segment Reporting Information [Line Items]
Revenues	502,827	520,677	1,351,089	1,384,092
Segment net income (loss)	83,599	103,389	143,381	151,882
Natural Gas Operations \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	502,827	520,677	1,351,089	1,384,092
Natural Gas Operations \| Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Utility Infrastructure Services
Segment Reporting Information [Line Items]
Revenues	333,493	312,862	1,771,609	1,575,130
Segment net income (loss)	(10,204)	(8,031)	50,231	47,947
Utility Infrastructure Services \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	300,291	274,189	1,618,354	1,427,701
Utility Infrastructure Services \| Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	$ 33,202	$ 38,673	$ 153,255	$ 147,429

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details