0001692115-20-000064 | 10-Q | XBRL Viewer | Southwest GAS Holdings INC

Cover - shares	9 Months Ended
Cover - shares	Sep. 30, 2020	Oct. 30, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 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	8360 S. Durango Drive
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		56,464,880
Entity Central Index Key	0001692115
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Southwest Gas Corporation
Entity Information [Line Items]
Document Type	10-Q
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	8360 S. Durango Drive
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	Q3
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Utility plant:
Gas plant	$ 8,219,196	$ 7,813,221
Less: accumulated depreciation	(2,394,730)	(2,313,050)
Construction work in progress	231,219	185,026
Net utility plant	6,055,685	5,685,197
Other property and investments	825,069	784,173
Current assets:
Cash and cash equivalents	23,945	49,539
Accounts receivable, net of allowances	513,017	474,097
Accrued utility revenue	36,500	79,100
Income taxes receivable, net	7,934	31,751
Deferred purchased gas costs	0	44,412
Prepaid and other current assets	151,432	180,957
Total current assets	732,828	859,856
Noncurrent assets:
Goodwill	340,197	343,023
Deferred income taxes	841	856
Deferred charges and other assets	475,037	496,943
Total noncurrent assets	816,075	840,822
Total assets	8,429,657	8,170,048
Capitalization:
Common stock, $1 par (authorized - 120,000,000 shares; issued and outstanding - 56,459,346 and 55,007,433 shares)	58,089	56,637
Additional paid-in capital	1,559,814	1,466,937
Accumulated other comprehensive loss, net	(52,783)	(56,732)
Retained earnings	1,054,118	1,039,072
Total equity	2,619,238	2,505,914
Redeemable noncontrolling interest	107,284	84,542
Long-term debt, less current maturities	2,685,722	2,300,482
Total capitalization	5,412,244	4,890,938
Current liabilities:
Current maturities of long-term debt	44,903	163,512
Short-term debt	54,000	211,000
Accounts payable	175,507	238,921
Customer deposits	69,122	69,165
Income taxes payable, net	1,084	2,069
Accrued general taxes	59,958	48,160
Accrued interest	35,478	21,329
Deferred purchased gas costs	76,242	60,755
Other current liabilities	322,928	264,950
Total current liabilities	839,222	1,079,861
Deferred income taxes and other credits:
Deferred income taxes and investment tax credits, net	639,002	599,840
Accumulated removal costs	401,000	395,000
Other deferred credits and other long-term liabilities	1,138,189	1,204,409
Total deferred income taxes and other credits	2,178,191	2,199,249
Total capitalization and liabilities	8,429,657	8,170,048
Southwest Gas Corporation
Utility plant:
Gas plant	8,219,196	7,813,221
Less: accumulated depreciation	(2,394,730)	(2,313,050)
Construction work in progress	231,219	185,026
Net utility plant	6,055,685	5,685,197
Other property and investments	135,734	133,787
Current assets:
Cash and cash equivalents	22,234	40,489
Accounts receivable, net of allowances	80,665	150,793
Accrued utility revenue	36,500	79,100
Income taxes receivable, net	5,032	25,901
Deferred purchased gas costs	0	44,412
Prepaid and other current assets	130,191	165,639
Total current assets	274,622	506,334
Noncurrent assets:
Goodwill	10,095	10,095
Deferred charges and other assets	455,434	463,333
Total noncurrent assets	465,529	473,428
Total assets	6,931,570	6,798,746
Capitalization:
Common stock, $1 par (authorized - 120,000,000 shares; issued and outstanding - 56,459,346 and 55,007,433 shares)	49,112	49,112
Additional paid-in capital	1,363,441	1,229,083
Accumulated other comprehensive loss, net	(50,015)	(55,151)
Retained earnings	781,735	782,108
Total equity	2,144,273	2,005,152
Long-term debt, less current maturities	2,345,876	1,991,333
Total capitalization	4,490,149	3,996,485
Current liabilities:
Current maturities of long-term debt	0	125,000
Short-term debt	0	194,000
Accounts payable	97,354	149,368
Customer deposits	69,122	69,165
Accrued general taxes	59,958	48,160
Accrued interest	35,247	21,256
Deferred purchased gas costs	76,242	60,755
Payable to parent	64	844
Other current liabilities	137,968	126,573
Total current liabilities	475,955	795,121
Deferred income taxes and other credits:
Deferred income taxes and investment tax credits, net	566,305	539,050
Accumulated removal costs	401,000	395,000
Other deferred credits and other long-term liabilities	998,161	1,073,090
Total deferred income taxes and other credits	1,965,466	2,007,140
Total capitalization and liabilities	$ 6,931,570	$ 6,798,746

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 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)	56,459,346	55,007,433
Common stock, outstanding (in shares)	56,459,346	55,007,433

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating revenues:
Gas operating revenues	$ 210,834	$ 209,980	$ 976,095	$ 989,368	$ 1,355,666	$ 1,359,581
Utility infrastructure services revenues	203,082	200,256	966,941	1,005,844	1,346,391	1,374,724
Total operating revenues	791,226	725,230	2,384,793	2,271,780	3,232,930	3,058,434
Operating expenses:
Net cost of gas sold	36,321	35,068	264,615	292,854	356,925	393,141
Operations and maintenance	101,764	109,652	304,964	321,190	407,924	414,289
Depreciation and amortization	80,139	75,370	245,009	223,251	324,995	286,522
Taxes other than income taxes	15,787	15,308	47,507	46,640	63,195	61,579
Utility infrastructure services expenses	502,951	451,574	1,252,489	1,154,238	1,671,478	1,534,442
Total operating expenses	736,962	686,972	2,114,584	2,038,173	2,824,517	2,689,973
Operating income (loss)	54,264	38,258	270,209	233,607	408,413	368,461
Other income and (expenses):
Net interest deductions	(28,311)	(27,434)	(83,141)	(80,662)	(111,705)	(106,502)
Other income (deductions)	1,799	(1,158)	(11,046)	6,827	(7,788)	(4,448)
Total other income and (expenses)	(26,512)	(28,592)	(94,187)	(73,835)	(119,493)	(110,950)
Income (loss) before income taxes	27,752	9,666	176,022	159,772	288,920	257,511
Income tax expense (benefit)	6,689	3,141	42,073	35,031	63,065	63,294
Net income (loss)	21,063	6,525	133,949	124,741	225,855	194,217
Net income attributable to noncontrolling interest	2,790	1,172	5,169	2,523	5,357	2,695
Net income attributable to Southwest Gas Holdings, Inc.	$ 18,273	$ 5,353	$ 128,780	$ 122,218	$ 220,498	$ 191,522
Earnings per share:
Basic (in USD per share)	$ 0.32	$ 0.10	$ 2.31	$ 2.26	$ 3.97	$ 3.60
Diluted (in USD per share)	$ 0.32	$ 0.10	$ 2.31	$ 2.26	$ 3.97	$ 3.59
Weighted average shares:
Basic (in shares)	56,271	54,670	55,683	53,996	55,508	53,219
Diluted (in shares)	56,357	54,748	55,753	54,063	55,577	53,287
Southwest Gas Corporation
Operating revenues:
Gas operating revenues	$ 210,834	$ 209,980	$ 976,095	$ 989,368	$ 1,355,666	$ 1,359,581
Operating expenses:
Net cost of gas sold	36,321	35,068	264,615	292,854	356,925	393,141
Operations and maintenance	101,159	109,039	303,567	319,572	406,169	412,330
Depreciation and amortization	55,942	52,372	173,865	159,327	230,158	205,594
Taxes other than income taxes	15,787	15,308	47,507	46,640	63,195	61,579
Total operating expenses	209,209	211,787	789,554	818,393	1,056,447	1,072,644
Operating income (loss)	1,625	(1,807)	186,541	170,975	299,219	286,937
Other income and (expenses):
Net interest deductions	(26,103)	(23,619)	(75,152)	(70,063)	(100,115)	(92,000)
Other income (deductions)	1,751	(1,353)	(10,947)	6,185	(7,615)	(5,194)
Total other income and (expenses)	(24,352)	(24,972)	(86,099)	(63,878)	(107,730)	(97,194)
Income (loss) before income taxes	(22,727)	(26,779)	100,442	107,097	191,489	189,743
Income tax expense (benefit)	(6,754)	(6,767)	20,874	20,351	35,496	43,456
Net income (loss)	(15,973)	(20,012)	79,568	86,746	155,993	146,287
Net income attributable to Southwest Gas Holdings, Inc.	(15,973)	(20,012)			155,993	146,287
Centuri
Operating revenues:
Utility infrastructure services revenues	$ 580,392	$ 515,250	$ 1,408,698	$ 1,282,412	$ 1,877,264	$ 1,698,853

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net income	$ 21,063	$ 6,525	$ 133,949	$ 124,741	$ 225,855	$ 194,217
Defined benefit pension plans:
Net actuarial loss	0	0	0	0	(54,026)	(15,524)
Amortization of prior service cost	220	241	659	724	901	977
Amortization of net actuarial loss	7,187	4,442	21,563	13,325	26,004	19,713
Prior service cost	0	0	0	0	(1,426)	0
Regulatory adjustment	(6,380)	(4,065)	(19,140)	(12,193)	21,130	(1,214)
Net defined benefit pension plans	1,027	618	3,082	1,856	(7,417)	3,952
Forward-starting interest rate swaps (“FSIRS”):
Amounts reclassified into net income	783	635	2,054	1,906	2,689	2,540
Net forward-starting interest rate swaps	783	635	2,054	1,906	2,689	2,540
Foreign currency translation adjustments	1,024	(447)	(1,187)	1,131	(280)	(877)
Total other comprehensive income (loss), net of tax	2,834	806	3,949	4,893	(5,008)	5,615
Comprehensive income (loss)	23,897	7,331	137,898	129,634	220,847	199,832
Comprehensive income attributable to noncontrolling interest	2,790	1,172	5,169	2,523	5,357	2,695
Comprehensive income attributable to Southwest Gas Holdings, Inc.	21,107	6,159	132,729	127,111	215,490	197,137
Southwest Gas Corporation
Net income	(15,973)	(20,012)	79,568	86,746	155,993	146,287
Defined benefit pension plans:
Net actuarial loss	0	0	0	0	(54,026)	(15,524)
Amortization of prior service cost	220	241	659	724	901	977
Amortization of net actuarial loss	7,187	4,442	21,563	13,325	26,004	19,713
Prior service cost	0	0	0	0	(1,426)	0
Regulatory adjustment	(6,380)	(4,065)	(19,140)	(12,193)	21,130	(1,214)
Net defined benefit pension plans	1,027	618	3,082	1,856	(7,417)	3,952
Forward-starting interest rate swaps (“FSIRS”):
Amounts reclassified into net income	783	635	2,054	1,906	2,689	2,540
Net forward-starting interest rate swaps	783	635	2,054	1,906	2,689	2,540
Total other comprehensive income (loss), net of tax	1,810	1,253	5,136	3,762	(4,728)	6,492
Comprehensive income (loss)	$ (14,163)	$ (18,759)	$ 84,704	$ 90,508	$ 151,265	$ 152,779

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	$ 21,063	$ 6,525	$ 133,949	$ 124,741	$ 225,855		$ 194,217
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	80,139	75,370	245,009	223,251	324,995		286,522
Deferred income taxes			37,752	46,099	45,815		60,930
Changes in current assets and liabilities:
Accounts receivable, net of allowances			(42,139)	(19,615)	(76,769)		(33,818)
Accrued utility revenue			42,600	41,400	(700)		(1,200)
Deferred purchased gas costs			59,899	(36,608)	38,016		(54,797)
Accounts payable			(59,031)	(46,079)	(14,817)		14,317
Accrued taxes			17,991	(2,841)	26,075		(4,956)
Other current assets and liabilities			121,185	74,048	121,274		18,730
Gains on sale of equipment			(581)	(3,157)	(2,897)		(3,863)
Changes in undistributed stock compensation			5,789	6,067	6,618		7,492
Equity AFUDC			(3,413)	(3,179)	(4,395)		(5,772)
Changes in deferred charges and other assets			(19,174)	(15,855)	(24,370)		(11,096)
Changes in other liabilities and deferred credits			(52,018)	(9,786)	(54,996)		33,243
Net cash provided by operating activities			487,818	378,486	609,704		499,949
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions			(632,474)	(719,386)	(851,236)		(925,135)
Acquisition of businesses, net of cash acquired			(250)	(19,533)	(28,355)		(266,697)
Changes in customer advances			7,691	15,049	11,643		17,461
Other			6,520	12,862	8,811		13,376
Net cash used in investing activities			(618,513)	(711,008)	(859,137)		(1,160,995)
CASH FLOW FROM FINANCING ACTIVITIES:
Issuance of common stock, net			90,635	129,341	119,240		391,509
Dividends paid			(93,317)	(86,345)	(123,099)		(112,050)
Issuance of long-term debt, net			650,619	482,614	699,601		566,793
Retirement of long-term debt			(289,295)	(127,175)	(375,909)		(221,176)
Change in credit facility and commercial paper			(92,000)	0	(92,000)		0
Change in short-term debt			(157,000)	(122,000)	24,000		(1,500)
Principal payments on finance lease obligations			(151)	(161)	(202)		(387)
Withholding remittance - share-based compensation			(2,736)	(1,858)	(2,736)		(2,088)
Other			(1,445)	1,167	(3,888)		(456)
Net cash provided by financing activities			105,310	275,583	245,007		620,645
Effects of currency translation on cash and cash equivalents			(209)	58	(109)		(289)
Change in cash and cash equivalents			(25,594)	(56,881)	(4,535)		(40,690)
Cash and cash equivalents at beginning of period			49,539	85,361	28,480		69,170
Cash and cash equivalents at end of period	23,945	28,480	23,945	28,480	23,945		28,480
SUPPLEMENTAL INFORMATION:
Interest paid, net of amounts capitalized			63,743	62,165	103,836		99,159
Income taxes paid (received), net			(16,006)	371	(13,625)		(16,669)
Southwest Gas Corporation
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	(15,973)	(20,012)	79,568	86,746	155,993		146,287
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	55,942	52,372	173,865	159,327	230,158		205,594
Deferred income taxes			25,633	35,899	23,415		45,659
Changes in current assets and liabilities:
Accounts receivable, net of allowances			70,129	66,527	(7,135)		(3,436)
Accrued utility revenue			42,600	41,400	(700)		(1,200)
Deferred purchased gas costs			59,899	(36,608)	38,016		(54,797)
Accounts payable			(50,314)	(77,311)	(476)		(686)
Accrued taxes			15,914	(4,419)	29,228		(7,125)
Other current assets and liabilities			74,892	87,869	76,194		31,579
Changes in undistributed stock compensation			4,492	4,710	4,928		5,796
Equity AFUDC			(3,413)	(3,179)	(4,395)		(5,772)
Changes in deferred charges and other assets			(27,688)	(21,098)	(38,357)		(17,122)
Changes in other liabilities and deferred credits			(52,532)	(10,357)	(55,536)		19,762
Net cash provided by operating activities			413,045	329,506	451,333		364,539
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions			(525,221)	(587,405)	(716,564)		(784,237)
Changes in customer advances			7,691	15,049	11,643		17,461
Other			183	(51)	139		(1,353)
Net cash used in investing activities			(517,347)	(572,407)	(704,782)		(768,129)
CASH FLOW FROM FINANCING ACTIVITIES:
Contributions from parent			131,961	126,186	165,711		149,091
Dividends paid			(77,500)	(71,000)	(102,400)		(93,000)
Issuance of long-term debt, net			446,508	297,222	446,508		297,222
Retirement of long-term debt			(125,000)	0		$ (125,000)		$ 0
Change in credit facility and commercial paper			(92,000)	0	(92,000)		0
Change in short-term debt			(194,000)	(122,000)	(30,000)		21,000
Withholding remittance - share-based compensation			(2,736)	(1,857)	(2,737)		(2,087)
Other			(1,186)	(801)	(1,210)		(890)
Net cash provided by financing activities			86,047	227,750	258,872		371,336
Change in cash and cash equivalents			(18,255)	(15,151)	5,423		(32,254)
Cash and cash equivalents at beginning of period			40,489	31,962	16,811		49,065
Cash and cash equivalents at end of period	$ 22,234	$ 16,811	22,234	16,811	22,234		16,811
SUPPLEMENTAL INFORMATION:
Interest paid, net of amounts capitalized			57,168	51,720	94,106		82,539
Income taxes paid (received), net			$ (22,962)	$ (22)	$ (22,262)		$ (17,164)

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.	Noncontrolling interest
Beginning balance (in shares) at Dec. 31, 2018			53,026,000
Beginning balance at Dec. 31, 2018			$ 54,656		$ 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)			1,598,000
Common stock issuances			$ 1,598		132,416
Change in ownership of noncontrolling interest					(452)							452
Foreign currency exchange translation adjustment							1,131
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax							1,856	1,856
FSIRS amounts reclassified to net income, net of tax	$ 1,906	$ 1,906					1,906	1,906
Net income									122,218	86,746
Share-based compensation						3,317				(465)
Contributions from Southwest Gas Holdings, Inc.						126,186
Dividends declared									(89,005)	(72,400)
Redemption value adjustments									0
Ending balance (in shares) at Sep. 30, 2019			54,624,000	47,482,000
Ending balance at Sep. 30, 2019	$ 2,423,710	1,929,606	$ 56,254	$ 49,112	1,437,733	1,194,745	(47,775)	(45,287)	977,498	731,036	$ 2,423,710	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 1.635
Beginning balance (in shares) at Jun. 30, 2019			54,321,000
Beginning balance at Jun. 30, 2019			$ 55,951		1,409,923	1,169,549	(48,581)	(46,540)	1,002,070	776,101		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)			303,000
Common stock issuances			$ 303		27,810
Change in ownership of noncontrolling interest					0							0
Foreign currency exchange translation adjustment							(447)
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax							618	618
FSIRS amounts reclassified to net income, net of tax	$ 635	635					635	635
Net income									5,353	(20,012)
Share-based compensation						1,102				(153)
Contributions from Southwest Gas Holdings, Inc.						24,094
Dividends declared									(29,925)	(24,900)
Redemption value adjustments									0
Ending balance (in shares) at Sep. 30, 2019			54,624,000	47,482,000
Ending balance at Sep. 30, 2019	$ 2,423,710	1,929,606	$ 56,254	$ 49,112	1,437,733	1,194,745	(47,775)	(45,287)	977,498	731,036	2,423,710	0
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	$ 2,689	2,689
Ending balance (in shares) at Sep. 30, 2020	56,459,346		56,459,000	47,482,000
Ending balance at Sep. 30, 2020	$ 2,619,238	2,144,273	$ 58,089	$ 49,112	1,559,814	1,363,441	(52,783)	(50,015)	1,054,118	781,735	2,619,238	0
Beginning balance (in shares) at Dec. 31, 2019	55,007,433		55,007,000
Beginning balance at Dec. 31, 2019			$ 56,637		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)			1,452,000
Common stock issuances			$ 1,452		92,877
Change in ownership of noncontrolling interest					0							0
Foreign currency exchange translation adjustment							(1,187)
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax							3,082	3,082
FSIRS amounts reclassified to net income, net of tax	$ 2,054	2,054					2,054	2,054
Net income									128,780	79,568
Share-based compensation						2,397				(641)
Contributions from Southwest Gas Holdings, Inc.						131,961
Dividends declared									(96,161)	(79,300)
Redemption value adjustments	$ 17,573								(17,573)
Ending balance (in shares) at Sep. 30, 2020	56,459,346		56,459,000	47,482,000
Ending balance at Sep. 30, 2020	$ 2,619,238	2,144,273	$ 58,089	$ 49,112	1,559,814	1,363,441	(52,783)	(50,015)	1,054,118	781,735	2,619,238	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 1.71
Beginning balance (in shares) at Jun. 30, 2020			55,910,000
Beginning balance at Jun. 30, 2020			$ 57,540		1,523,630	1,329,843	(55,617)	(51,825)	1,085,742	824,847		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)			549,000
Common stock issuances			$ 549		36,184
Change in ownership of noncontrolling interest					0							0
Foreign currency exchange translation adjustment							1,024
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax							1,027	1,027
FSIRS amounts reclassified to net income, net of tax	$ 783	783					783	783
Net income									18,273	(15,973)
Share-based compensation						1,137				(139)
Contributions from Southwest Gas Holdings, Inc.						32,461
Dividends declared									(32,324)	(27,000)
Redemption value adjustments	$ 17,600								(17,573)
Ending balance (in shares) at Sep. 30, 2020	56,459,346		56,459,000	47,482,000
Ending balance at Sep. 30, 2020	$ 2,619,238	$ 2,144,273	$ 58,089	$ 49,112	$ 1,559,814	$ 1,363,441	$ (52,783)	$ (50,015)	$ 1,054,118	$ 781,735	$ 2,619,238	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 0.57

Background, Organization, and Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 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 primarily from installation, replacement, repair, and maintenance of energy distribution systems. 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.

These condensed consolidated financial statements should 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)	September 30, 2020		December 31, 2019
Southwest Gas Corporation:
Net cash surrender value of COLI policies	$	133,761	$	132,072
Other property	1,973		1,715
Total Southwest Gas Corporation	135,734		133,787
Centuri property, equipment, and intangibles	1,073,092		983,905
Centuri accumulated provision for depreciation and amortization	(406,590)		(352,333)
Other property	22,833		18,814
Total Southwest Gas Holdings, Inc.	$	825,069	$	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 of Southwest and the Company include money market fund investments totaling approximately $40,000 for both entities at September 30, 2020, and $23.5 million and $26.7 million, for each, 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. 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 payment 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 ongoing COVID-19 pandemic, Southwest continued the moratorium initiated in March 2020 on disconnection of natural gas service for non-payment and also ceased charging late fees until further notice. While the moratorium continues to be in place, Southwest is actively working with customers experiencing financial hardship by means of flexible payment options. Management continues to monitor expected credit losses in light of the evolving financial impact of COVID-19. The allowance as of September 30, 2020 reflects the expected impact from the pandemic on balances as of that date, including consideration of customers’ ability to pay currently and once the moratorium is lifted.

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 estimated future 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 the current environment surrounding COVID-19 given the nature of its customers.

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

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 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 $55 million at September 30, 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 September 30, 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 first nine months 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. Goodwill on Southwest’s and the Company’s Condensed Consolidated Balance Sheets includes:


(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services		Total Company
December 31, 2019	$	10,095	$	332,928	$	343,023
Foreign currency translation adjustment	—		(2,826)		(2,826)
September 30, 2020	$	10,095	$	330,102	$	340,197

Other Current Liabilities. Management recognizes in its balance sheets various liabilities that are expected to be settled through future cash payment within the next twelve months, including 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 includes $27 million and $25.2 million of dividends declared by Southwest Gas Corporation, but not yet paid to Southwest Gas Holdings, Inc. as of September 30, 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 September 30,				Nine Months Ended September 30,				Twelve Months Ended September 30,
(Thousands of dollars)	2020		2019		2020		2019		2020		2019
Southwest Gas Corporation - natural gas operations segment:
Change in COLI policies	$	4,500	$	200	$	1,000	$	11,200	$	7,200	$	2,000
Interest income	1,412		1,521		3,214		4,940		4,630		6,659
Equity AFUDC	1,232		1,212		3,413		3,179		4,395		5,772
Other components of net periodic benefit cost	(5,005)		(3,765)		(15,016)		(11,295)		(18,780)		(16,560)
Miscellaneous income and (expense)	(388)		(521)		(3,558)		(1,839)		(5,060)		(3,065)
Southwest Gas Corporation - total other income (deductions)	1,751		(1,353)		(10,947)		6,185		(7,615)		(5,194)
Utility infrastructure services segment:
Interest income	—		—		—		—		—		82
Foreign transaction gain (loss)	—		(6)		(16)		546		(16)		66
Miscellaneous income and (expense)	48		177		(91)		23		(194)		514
Centuri - total other income (deductions)	48		171		(107)		569		(210)		662
Corporate and administrative	—		24		8		73		37		84
Consolidated Southwest Gas Holdings, Inc. - total other income (deductions)	$	1,799	$	(1,158)	$	(11,046)	$	6,827	$	(7,788)	$	(4,448)

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 remaining Swaps as of September 30, 2020 matured in October 2020.

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

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. Based on the fair value model employed, the estimated redemption value of the redeemable noncontrolling interest increased by approximately $17.6 million during the third quarter of 2020. Adjustment to the redemption value also impacts retained earnings, as reflected in the Company’s Condensed Consolidated Statement of Equity, but does not impact net income. 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	5,169
Redemption value adjustment	17,573
Balance, September 30, 2020	$	107,284

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


	Three Months Ended September 30,		Nine Months Ended September 30,		Twelve Months Ended September 30,
(In thousands)	2020	2019	2020	2019	2020	2019
Weighted average basic shares	56,271	54,670	55,683	53,996	55,508	53,219
Effect of dilutive securities:
Management Incentive Plan shares	—	12	—	11	3	15
Restricted stock units (1)	86	66	70	56	66	53
Weighted average diluted shares	56,357	54,748	55,753	54,063	55,577	53,287

(1) The number of securities included 76,000 and 55,000 performance shares during the three months ending September 30, 2020 and 2019, 63,000 and 48,000 performance shares during the nine months ending September 30, 2020 and 2019, and 57,000 and 44,000 performance shares during the twelve months ending September 30, 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 Financial Accounting Standards Board (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 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 previously 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 its periodic 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, which did not result in a material impact to the Company’s or Southwest’s consolidated financial statements.

Recently issued accounting pronouncements that will be effective after 2020:

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, including when modifying a contract (during the eligibility period covered by the update to Topic 848) to replace a reference rate affected by reference rate reform. The update applies only to contracts and hedging relationships that reference the London Interbank Offered Rate (“LIBOR”) or another reference rate expected to be discontinued due to reference rate reform. The guidance was eligible to be applied upon issuance on March 12, 2020, and can generally be applied through December 31, 2022. Management will monitor the impacts this update might have on the Company’s and Southwest’s consolidated financial statements and disclosures, and will reflect such appropriately, in the event that the optional guidance is elected. See also LIBOR discussion in Note 5 – Debt.

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

Components of Net Periodic Benefit Cost

9 Months Ended

Sep. 30, 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 is a component 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
	September 30,
	Three Months				Nine Months				Twelve Months
	2020		2019		2020		2019		2020		2019
(Thousands of dollars)
Service cost	$	8,576	$	6,466	$	25,725	$	19,398	$	32,191	$	26,536
Interest cost	11,388		12,252		34,165		36,755		46,416		47,799
Expected return on plan assets	(16,324)		(15,061)		(48,972)		(45,183)		(64,033)		(59,872)
Amortization of net actuarial loss	9,006		5,589		27,019		16,767		32,608		24,796
Net periodic benefit cost	$	12,646	$	9,246	$	37,937	$	27,737	$	47,182	$	39,259

	SERP
	September 30,
	Three Months				Nine Months				Twelve Months
	2020		2019		2020		2019		2020		2019
(Thousands of dollars)
Service cost	$	97	$	66	$	292	$	199	$	359	$	261
Interest cost	401		440		1,204		1,320		1,644		1,734
Amortization of net actuarial loss	451		255		1,353		765		1,608		1,141
Net periodic benefit cost	$	949	$	761	$	2,849	$	2,284	$	3,611	$	3,136

	PBOP
	September 30,
	Three Months				Nine Months				Twelve Months
	2020		2019		2020		2019		2020		2019
(Thousands of dollars)
Service cost	$	395	$	319	$	1,186	$	957	$	1,505	$	1,325
Interest cost	646		761		1,936		2,285		2,697		2,972
Expected return on plan assets	(852)		(789)		(2,556)		(2,367)		(3,345)		(3,296)
Amortization of prior service costs	289		318		867		953		1,185		1,286

Net periodic benefit cost	$	478	$	609	$	1,433	$	1,828	$	2,042	$	2,287

Revenue

9 Months Ended

Sep. 30, 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 September 30,				Nine Months Ended September 30,				Twelve Months Ended September 30,
(Thousands of dollars)	2020		2019		2020		2019		2020		2019
Residential	$	131,008	$	124,169	$	690,861	$	706,270	$	957,379	$	961,928
Small commercial	35,204		39,725		159,122		179,519		228,720		250,986
Large commercial	9,942		10,945		32,588		36,030		45,493		49,288
Industrial/other	5,888		3,837		19,089		15,728		25,435		21,826
Transportation	21,040		21,580		65,281		68,297		89,364		90,696
Revenue from contracts with customers	203,082		200,256		966,941		1,005,844		1,346,391		1,374,724
Alternative revenue program revenues (deferrals)	9,199		7,957		9,545		(23,196)		7,629		(23,913)
Other revenues (1)	(1,447)		1,767		(391)		6,720		1,646		8,770
Total Gas operating revenues	$	210,834	$	209,980	$	976,095	$	989,368	$	1,355,666	$	1,359,581

(1) Amounts include late fees and other miscellaneous revenues, and may also include the impact of certain regulatory mechanisms, such as cost-of-service components in current customer rates that are expected to be returned to customers in future periods.

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 September 30,				Nine Months Ended September 30,				Twelve Months Ended September 30,
(Thousands of dollars)	2020		2019		2020		2019		2020		2019
Service Types:
Gas infrastructure services	$	387,578	$	364,241	$	935,444	$	885,950	$	1,288,468	$	1,160,017
Electric power infrastructure services	115,386		70,610		282,992		184,277		346,432		202,844
Other	77,428		80,399		190,262		212,185		242,364		335,992
Total Utility infrastructure services revenues	$	580,392	$	515,250	$	1,408,698	$	1,282,412	$	1,877,264	$	1,698,853


	Three Months Ended September 30,				Nine Months Ended September 30,				Twelve Months Ended September 30,
(Thousands of dollars)	2020		2019		2020		2019		2020		2019
Contract Types:
Master services agreement	$	437,914	$	410,283	$	1,076,961	$	1,021,798	$	1,438,540	$	1,291,397
Bid contract	142,478		104,967		331,737		260,614		438,724		407,456
Total Utility infrastructure services revenues	$	580,392	$	515,250	$	1,408,698	$	1,282,412	$	1,877,264	$	1,698,853

Unit price contracts	$	377,284	$	415,404	$	985,673	$	1,006,577	$	1,359,352	$	1,316,404
Fixed price contracts	46,379		37,539		109,935		80,503		142,356		152,890
Time and materials contracts	156,729		62,307		313,090		195,332		375,556		229,559
Total Utility infrastructure services revenues	$	580,392	$	515,250	$	1,408,698	$	1,282,412	$	1,877,264	$	1,698,853

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 September 30, 2020 and December 31, 2019 on the Company’s Condensed Consolidated Balance Sheets:


(Thousands of dollars)	September 30, 2020		December 31, 2019
Contracts receivable, net	$	275,598	$	223,904
Revenue earned on contracts in progress in excess of billings	156,754		99,399
Amounts billed in excess of revenue earned on contracts	5,522		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 September 30, 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 September 30, 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 September 30, 2020 was $55.3 million. Centuri expects to recognize the remaining performance obligations over approximately the next year; 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)	September 30, 2020		December 31, 2019
Billed on completed contracts and contracts in progress	$	271,872	$	216,268
Other receivables	5,214		8,456
Contracts receivable, gross	277,086		224,724
Allowance for doubtful accounts	(1,488)		(820)
Contracts receivable, net	$	275,598	$	223,904

- Definition

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

+ References

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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

+ Details

Common Stock

9 Months Ended

Sep. 30, 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 following table provides the activity under the Equity Shelf Program for the three-month and life-to-date periods ended September 30, 2020:


	Three Months Ended		Life-To-Date Ended
	September 30, 2020
Gross proceeds	$	32,788,633	$	207,125,867
Less: agent commissions	(327,886)		(2,071,259)
Net proceeds	$	32,460,747	$	205,054,608
Number of shares sold	506,219		2,705,376
Weighted average price per share	$	64.77	$	76.56

As of September 30, 2020, the Company had up to $92,874,133 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 nine months ended September 30, 2020, the Company issued approximately 96,000 shares of common stock through the Restricted Stock/Unit Plan and Management Incentive Plan.

Additionally, during the nine months ended September 30, 2020, the Company issued 130,000 shares of common stock through the Dividend Reinvestment and Stock Purchase Plan, raising approximately $9 million.

Debt

9 Months Ended

Sep. 30, 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.

The fair values of 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.


	September 30, 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	$	126,673
Notes, 6.1%, due 2041	125,000		172,353		125,000		162,666
Notes, 3.875%, due 2022	250,000		260,388		250,000		258,550
Notes, 4.875%, due 2043	250,000		317,325		250,000		291,928
Notes, 3.8%, due 2046	300,000		335,970		300,000		308,307
Notes, 3.7%, due 2028	300,000		341,388		300,000		320,685
Notes, 4.15%, due 2049	300,000		361,053		300,000		330,138
Notes, 2.2%, due 2030	450,000		471,227		—		—
8% Series, due 2026	75,000		99,423		75,000		96,905
Medium-term notes, 7.78% series, due 2022	25,000		26,944		25,000		27,500
Medium-term notes, 7.92% series, due 2027	25,000		33,716		25,000		32,543
Medium-term notes, 6.76% series, due 2027	7,500		9,569		7,500		9,156
Unamortized discount and debt issuance costs	(18,091)				(14,450)
	2,089,409				1,768,050
Revolving credit facility and commercial paper	58,000		58,000		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	(1,533)				(1,717)
	198,467				198,283
Less: current maturities	—				(125,000)
Long-term debt, less current maturities - Southwest Gas Corporation	$	2,345,876			$	1,991,333
Centuri:
Centuri term loan facility	$	231,010	$	236,477	$	244,812	$	252,182
Unamortized debt issuance costs	(890)				(1,101)
	230,120				243,711
Centuri secured revolving credit facility	59,908		59,950		60,021		60,057
Centuri other debt obligations	94,721		97,120		43,929		44,787
Less: current maturities	(44,903)				(38,512)
Long-term debt, less current maturities - Centuri	$	339,846			$	309,149
Consolidated Southwest Gas Holdings, Inc.:
Southwest Gas Corporation long-term debt	$	2,345,876			$	2,116,333
Centuri long-term debt	384,749				347,661
Less: current maturities	(44,903)				(163,512)
Long-term debt, less current maturities - Southwest Gas Holdings, Inc.	$	2,685,722			$	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 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 September 30, 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 September 30, 2020, $58 million was outstanding on the long-term portion (including $50 million under the commercial paper program, discussed below) of the facility.

On April 10, 2020, Southwest amended its credit facility agreement; total borrowing capacity under the amended agreement remains at $400 million. The amended agreement extended the maturity date from March 2022 to April 2025. Under the amended agreement, the applicable margin will range 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 further 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 September 30, 2020, as noted above, $50 million of borrowings were outstanding under the commercial paper program.

In June 2020, Southwest issued $450 million aggregate principal amount of 2.20% Senior Notes at a discount of 0.126%. The notes will mature in June 2030. A portion of the net proceeds was used to reduce borrowings under Southwest’s credit facility and to redeem the 4.45% $125 million Notes due in December 2020, which were redeemed in September 2020 after Southwest provided advance notice to the holders of its intention to redeem the notes in full at a redemption price of 100% plus accrued and unpaid interest.

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; related 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 September 30, 2020 totaled $1.4 billion. At September 30, 2020, $291 million in borrowings were outstanding under Centuri’s combined secured revolving credit and term loan facility. During 2020, Centuri also received proceeds of $70 million in equipment loans, 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 $54 million outstanding under this credit facility as of September 30, 2020.

Similar to Southwest amending its credit facility agreement, on April 10, 2020, Southwest Gas Holdings, Inc. also amended its existing credit facility, extending the maturity date to April 2025. The revolving borrowing capacity under the amended agreement remained at $100 million, the same as before the amendment. Interest rate benchmarks (LIBOR or an alternative) as well as related ranges, including with regard to the applicable margin, largely mirror those included in Southwest’s amended facility agreement noted above, determined in this case based on Southwest Gas Holdings, Inc.’s senior unsecured long-term debt rating. Similar to the Southwest facility amendment, 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 its credit facility agreement with a replacement rate, as set forth in the amended agreement. The commitment fee rates, terms, and covenants, noted above for Southwest are also applicable to Southwest Gas Holdings, Inc. in its amended credit facility, including the noted ratio of funded debt to total capitalization as of the end of any quarter of any fiscal year.

As discussed previously, under Southwest’s $400 million credit facility, $250 million has been designated by management for working capital purposes. Southwest had no short-term borrowings outstanding at September 30, 2020 under this facility.

LIBOR

It is currently anticipated that LIBOR may be discontinued as a benchmark or reference rate after 2021. As of September 30, 2020, $54 million, $8 million and $172 million, respectively, for the holding company, Southwest, and Centuri, were outstanding under credit facilities whereby interest was with reference to LIBOR and for which facility maturity dates extend beyond 2021. As of September 30, 2020, these LIBOR-based borrowings represent approximately 0.3% of Southwest’s total debt, and 8% of total debt (including current maturities) for the Company overall. Southwest and Southwest Gas Holdings, Inc., in accordance with the April 2020 amendments to their respective facilities, 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 predictable or less attractive than LIBOR.

Other Comprehensive Income and Accumulated Other Comprehensive Income

9 Months Ended

Sep. 30, 2020

Equity [Abstract]

Other Comprehensive Income and Accumulated Other Comprehensive Income

Note 6 – Other Comprehensive Income and Accumulated Other Comprehensive Income

The following information presents 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 September 30, 2020						Three Months Ended September 30, 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	$	318	$	(77)	$	241
Amortization of net actuarial (gain)/loss	9,457		(2,270)		7,187		5,844		(1,402)		4,442
Regulatory adjustment	(8,394)		2,014		(6,380)		(5,348)		1,283		(4,065)
Pension plans other comprehensive income (loss)	1,352		(325)		1,027		814		(196)		618
FSIRS (designated hedging activities):
Amounts reclassified into net income	1,030		(247)		783		836		(201)		635
FSIRS other comprehensive income (loss)	1,030		(247)		783		836		(201)		635
Total other comprehensive income (loss) - Southwest Gas Corporation	2,382		(572)		1,810		1,650		(397)		1,253
Foreign currency translation adjustments:
Translation adjustments	1,024		—		1,024		(447)		—		(447)
Foreign currency other comprehensive income (loss)	1,024		—		1,024		(447)		—		(447)
Total other comprehensive income (loss) - Southwest Gas Holdings, Inc.	$	3,406	$	(572)	$	2,834	$	1,203	$	(397)	$	806

	Nine Months Ended September 30, 2020						Nine Months Ended September 30, 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	$	867	$	(208)	$	659	$	953	$	(229)	$	724
Amortization of net actuarial (gain)/loss	28,372		(6,809)		21,563		17,532		(4,207)		13,325
Regulatory adjustment	(25,184)		6,044		(19,140)		(16,043)		3,850		(12,193)
Pension plans other comprehensive income (loss)	4,055		(973)		3,082		2,442		(586)		1,856
FSIRS (designated hedging activities):
Amounts reclassified into net income	2,703		(649)		2,054		2,508		(602)		1,906
FSIRS other comprehensive income (loss)	2,703		(649)		2,054		2,508		(602)		1,906
Total other comprehensive income (loss) - Southwest Gas Corporation	6,758		(1,622)		5,136		4,950		(1,188)		3,762
Foreign currency translation adjustments:
Translation adjustments	(1,187)		—		(1,187)		1,131		—		1,131
Foreign currency other comprehensive income (loss)	(1,187)		—		(1,187)		1,131		—		1,131
Total other comprehensive income (loss) - Southwest Gas Holdings, Inc.	$	5,571	$	(1,622)	$	3,949	$	6,081	$	(1,188)	$	4,893


	Twelve Months Ended September 30, 2020						Twelve Months Ended September 30, 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	1,185		(284)		901		1,286		(309)		977
Amortization of net actuarial (gain)/loss	34,216		(8,212)		26,004		25,937		(6,224)		19,713
Prior service cost	(1,878)		452		(1,426)		—		—		—
Regulatory adjustment	27,803		(6,673)		21,130		(1,597)		383		(1,214)
Pension plans other comprehensive income (loss)	(9,761)		2,344		(7,417)		5,200		(1,248)		3,952
FSIRS (designated hedging activities):
Amounts reclassified into net income	3,539		(850)		2,689		3,344		(804)		2,540
FSIRS other comprehensive income (loss)	3,539		(850)		2,689		3,344		(804)		2,540
Total other comprehensive income (loss) - Southwest Gas Corporation	(6,222)		1,494		(4,728)		8,544		(2,052)		6,492
Foreign currency translation adjustments:
Translation adjustments	(280)		—		(280)		(877)		—		(877)
Foreign currency other comprehensive income (loss)	(280)		—		(280)		(877)		—		(877)
Total other comprehensive income (loss) - Southwest Gas Holdings, Inc.	$	(6,502)	$	1,494	$	(5,008)	$	7,667	$	(2,052)	$	5,615

(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 $1.7 million of realized losses (net of tax) related to the remaining balance of Southwest’s forward-starting interest rate swaps (“FSIRS”), included in AOCI at September 30, 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	—		—		—		—		—		—		(1,187)		—		(1,187)		(1,187)
Other comprehensive income (loss) before reclassifications	—		—		—		—		—		—		(1,187)		—		(1,187)		(1,187)
FSIRS amounts reclassified from AOCI (1)	—		—		—		2,703		(649)		2,054		—		—		—		2,054
Amortization of prior service cost (2)	867		(208)		659		—		—		—		—		—		—		659
Amortization of net actuarial loss (2)	28,372		(6,809)		21,563		—		—		—		—		—		—		21,563
Regulatory adjustment (3)	(25,184)		6,044		(19,140)		—		—		—		—		—		—		(19,140)
Net current period other comprehensive income (loss) attributable to Southwest Gas Holdings, Inc.	4,055		(973)		3,082		2,703		(649)		2,054		(1,187)		—		(1,187)		3,949
Ending Balance AOCI September 30, 2020	$	(62,546)	$	15,012	$	(47,534)	$	(3,263)	$	782	$	(2,481)	$	(2,768)	$	—	$	(2,768)	$	(52,783)

(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)	—		—		—		2,703		(649)		2,054		2,054
Amortization of prior service cost (6)	867		(208)		659		—		—		—		659
Amortization of net actuarial loss (6)	28,372		(6,809)		21,563		—		—		—		21,563
Regulatory adjustment (7)	(25,184)		6,044		(19,140)		—		—		—		(19,140)
Net current period other comprehensive income attributable to Southwest Gas Corporation	4,055		(973)		3,082		2,703		(649)		2,054		5,136
Ending Balance AOCI September 30, 2020	$	(62,546)	$	15,012	$	(47,534)	$	(3,263)	$	782	$	(2,481)	$	(50,015)

(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)	September 30, 2020		December 31, 2019
Net actuarial loss	$	(454,702)	$	(483,074)
Prior service cost	(2,774)		(3,641)
Less: amount recognized in regulatory assets	394,930		420,114
Recognized in AOCI	$	(62,546)	$	(66,601)

Segment Information

9 Months Ended

Sep. 30, 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)	September 30, 2020		December 31, 2019
Centuri accounts receivable for services provided to Southwest	$	15,102	$	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 September 30, 2020
Revenues from external customers	$	210,834	$	548,300	$	—	$	759,134
Intersegment revenues	—		32,092		—		32,092
Total	$	210,834	$	580,392	$	—	$	791,226
Segment net income (loss)	$	(15,973)	$	34,873	$	(627)	$	18,273

Three Months Ended September 30, 2019
Revenues from external customers	$	209,980	$	480,896	$	—	$	690,876
Intersegment revenues	—		34,354		—		34,354
Total	$	209,980	$	515,250	$	—	$	725,230
Segment net income (loss)	$	(20,012)	$	25,838	$	(473)	$	5,353

(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services		Other		Total
Nine Months Ended September 30, 2020
Revenues from external customers	$	976,095	$	1,306,481	$	—	$	2,282,576
Intersegment revenues	—		102,217		—		102,217
Total	$	976,095	$	1,408,698	$	—	$	2,384,793
Segment net income (loss)	$	79,568	$	50,936	$	(1,724)	$	128,780

Nine Months Ended September 30, 2019
Revenues from external customers	$	989,368	$	1,160,303	$	—	$	2,149,671
Intersegment revenues	—		122,109		—		122,109
Total	$	989,368	$	1,282,412	$	—	$	2,271,780
Segment net income (loss)	$	86,746	$	36,725	$	(1,253)	$	122,218


(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services		Other		Total
Twelve Months Ended September 30, 2020
Revenues from external customers	$	1,355,666	$	1,738,430	$	—	$	3,094,096
Intersegment revenues	—		138,834		—		138,834
Total	$	1,355,666	$	1,877,264	$	—	$	3,232,930
Segment net income (loss)	$	155,993	$	66,615	$	(2,110)	$	220,498

Twelve Months Ended September 30, 2019
Revenues from external customers	$	1,359,581	$	1,537,508	$	—	$	2,897,089
Intersegment revenues	—		161,345		—		161,345
Total	$	1,359,581	$	1,698,853	$	—	$	3,058,434
Segment net income (loss)	$	146,287	$	46,668	$	(1,433)	$	191,522

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Background, Organization, and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 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 primarily from installation, replacement, repair, and maintenance of energy distribution systems. 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. These condensed consolidated financial statements should 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 of Southwest and the Company include money market fund investments totaling approximately $40,000 for both entities at September 30, 2020, and $23.5 million and $26.7 million, for each, 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. 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 payment 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 ongoing COVID-19 pandemic, Southwest continued the moratorium initiated in March 2020 on disconnection of natural gas service for non-payment and also ceased charging late fees until further notice. While the moratorium continues to be in place, Southwest is actively working with customers experiencing financial hardship by means of flexible payment options. Management continues to monitor expected credit losses in light of the evolving financial impact of COVID-19. The allowance as of September 30, 2020 reflects the expected impact from the pandemic on balances as of that date, including consideration of customers’ ability to pay currently and once the moratorium is lifted.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 estimated future 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 the current environment surrounding COVID-19 given the nature of its customers. Activity between periods in the allowance for uncollectibles and the balances as of the periods presented within the Company’s and Southwest’s financial statements were not material to the condensed consolidated financial statements overall.
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 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 Financial Accounting Standards Board (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 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 previously 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 its periodic 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, which did not result in a material impact to the Company’s or Southwest’s consolidated financial statements. Recently issued accounting pronouncements that will be effective after 2020: 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, including when modifying a contract (during the eligibility period covered by the update to Topic 848) to replace a reference rate affected by reference rate reform. The update applies only to contracts and hedging relationships that reference the London Interbank Offered Rate (“LIBOR”) or another reference rate expected to be discontinued due to reference rate reform. The guidance was eligible to be applied upon issuance on March 12, 2020, and can generally be applied through December 31, 2022. Management will monitor the impacts this update might have on the Company’s and Southwest’s consolidated financial statements and disclosures, and will reflect such appropriately, in the event that the optional guidance is elected. See also LIBOR discussion in Note 5 – Debt. In August 2020, the FASB issued ASU 2020-06 “Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging— Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity.” The update, amongst other amendments, improves the guidance related to the disclosures and earnings-per-share for convertible instruments and contracts in an entity’s own equity. The update is effective for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years; early adoption is permitted. Management is evaluating the impacts this update might have on the Company’s consolidated financial statements and disclosures.

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

9 Months Ended

Sep. 30, 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)	September 30, 2020		December 31, 2019
Southwest Gas Corporation:
Net cash surrender value of COLI policies	$	133,761	$	132,072
Other property	1,973		1,715
Total Southwest Gas Corporation	135,734		133,787
Centuri property, equipment, and intangibles	1,073,092		983,905
Centuri accumulated provision for depreciation and amortization	(406,590)		(352,333)
Other property	22,833		18,814
Total Southwest Gas Holdings, Inc.	$	825,069	$	784,173

Schedule of Goodwill

Goodwill on Southwest’s and the Company’s Condensed Consolidated Balance Sheets includes:


(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services		Total Company
December 31, 2019	$	10,095	$	332,928	$	343,023
Foreign currency translation adjustment	—		(2,826)		(2,826)
September 30, 2020	$	10,095	$	330,102	$	340,197

Schedule of Significant Items Included in 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 September 30,				Nine Months Ended September 30,				Twelve Months Ended September 30,
(Thousands of dollars)	2020		2019		2020		2019		2020		2019
Southwest Gas Corporation - natural gas operations segment:
Change in COLI policies	$	4,500	$	200	$	1,000	$	11,200	$	7,200	$	2,000
Interest income	1,412		1,521		3,214		4,940		4,630		6,659
Equity AFUDC	1,232		1,212		3,413		3,179		4,395		5,772
Other components of net periodic benefit cost	(5,005)		(3,765)		(15,016)		(11,295)		(18,780)		(16,560)
Miscellaneous income and (expense)	(388)		(521)		(3,558)		(1,839)		(5,060)		(3,065)
Southwest Gas Corporation - total other income (deductions)	1,751		(1,353)		(10,947)		6,185		(7,615)		(5,194)
Utility infrastructure services segment:
Interest income	—		—		—		—		—		82
Foreign transaction gain (loss)	—		(6)		(16)		546		(16)		66
Miscellaneous income and (expense)	48		177		(91)		23		(194)		514
Centuri - total other income (deductions)	48		171		(107)		569		(210)		662
Corporate and administrative	—		24		8		73		37		84
Consolidated Southwest Gas Holdings, Inc. - total other income (deductions)	$	1,799	$	(1,158)	$	(11,046)	$	6,827	$	(7,788)	$	(4,448)

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	5,169
Redemption value adjustment	17,573
Balance, September 30, 2020	$	107,284

Schedule of Earnings Per Share, Basic and Diluted

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


	Three Months Ended September 30,		Nine Months Ended September 30,		Twelve Months Ended September 30,
(In thousands)	2020	2019	2020	2019	2020	2019
Weighted average basic shares	56,271	54,670	55,683	53,996	55,508	53,219
Effect of dilutive securities:
Management Incentive Plan shares	—	12	—	11	3	15
Restricted stock units (1)	86	66	70	56	66	53
Weighted average diluted shares	56,357	54,748	55,753	54,063	55,577	53,287

Components of Net Periodic Benefit Cost (Tables)

9 Months Ended

Sep. 30, 2020

Retirement Benefits [Abstract]

Schedule of Net Periodic Benefit Costs


	Qualified Retirement Plan
	September 30,
	Three Months				Nine Months				Twelve Months
	2020		2019		2020		2019		2020		2019
(Thousands of dollars)
Service cost	$	8,576	$	6,466	$	25,725	$	19,398	$	32,191	$	26,536
Interest cost	11,388		12,252		34,165		36,755		46,416		47,799
Expected return on plan assets	(16,324)		(15,061)		(48,972)		(45,183)		(64,033)		(59,872)
Amortization of net actuarial loss	9,006		5,589		27,019		16,767		32,608		24,796
Net periodic benefit cost	$	12,646	$	9,246	$	37,937	$	27,737	$	47,182	$	39,259

	SERP
	September 30,
	Three Months				Nine Months				Twelve Months
	2020		2019		2020		2019		2020		2019
(Thousands of dollars)
Service cost	$	97	$	66	$	292	$	199	$	359	$	261
Interest cost	401		440		1,204		1,320		1,644		1,734
Amortization of net actuarial loss	451		255		1,353		765		1,608		1,141
Net periodic benefit cost	$	949	$	761	$	2,849	$	2,284	$	3,611	$	3,136

	PBOP
	September 30,
	Three Months				Nine Months				Twelve Months
	2020		2019		2020		2019		2020		2019
(Thousands of dollars)
Service cost	$	395	$	319	$	1,186	$	957	$	1,505	$	1,325
Interest cost	646		761		1,936		2,285		2,697		2,972
Expected return on plan assets	(852)		(789)		(2,556)		(2,367)		(3,345)		(3,296)
Amortization of prior service costs	289		318		867		953		1,185		1,286

Net periodic benefit cost	$	478	$	609	$	1,433	$	1,828	$	2,042	$	2,287

Revenue (Tables)

9 Months Ended

Sep. 30, 2020

Revenue from Contract with Customer [Abstract]

Summary of Revenue Disaggregated by Service Type and Contract Type


	Three Months Ended September 30,				Nine Months Ended September 30,				Twelve Months Ended September 30,
(Thousands of dollars)	2020		2019		2020		2019		2020		2019
Residential	$	131,008	$	124,169	$	690,861	$	706,270	$	957,379	$	961,928
Small commercial	35,204		39,725		159,122		179,519		228,720		250,986
Large commercial	9,942		10,945		32,588		36,030		45,493		49,288
Industrial/other	5,888		3,837		19,089		15,728		25,435		21,826
Transportation	21,040		21,580		65,281		68,297		89,364		90,696
Revenue from contracts with customers	203,082		200,256		966,941		1,005,844		1,346,391		1,374,724
Alternative revenue program revenues (deferrals)	9,199		7,957		9,545		(23,196)		7,629		(23,913)
Other revenues (1)	(1,447)		1,767		(391)		6,720		1,646		8,770
Total Gas operating revenues	$	210,834	$	209,980	$	976,095	$	989,368	$	1,355,666	$	1,359,581


	Three Months Ended September 30,				Nine Months Ended September 30,				Twelve Months Ended September 30,
(Thousands of dollars)	2020		2019		2020		2019		2020		2019
Service Types:
Gas infrastructure services	$	387,578	$	364,241	$	935,444	$	885,950	$	1,288,468	$	1,160,017
Electric power infrastructure services	115,386		70,610		282,992		184,277		346,432		202,844
Other	77,428		80,399		190,262		212,185		242,364		335,992
Total Utility infrastructure services revenues	$	580,392	$	515,250	$	1,408,698	$	1,282,412	$	1,877,264	$	1,698,853


	Three Months Ended September 30,				Nine Months Ended September 30,				Twelve Months Ended September 30,
(Thousands of dollars)	2020		2019		2020		2019		2020		2019
Contract Types:
Master services agreement	$	437,914	$	410,283	$	1,076,961	$	1,021,798	$	1,438,540	$	1,291,397
Bid contract	142,478		104,967		331,737		260,614		438,724		407,456
Total Utility infrastructure services revenues	$	580,392	$	515,250	$	1,408,698	$	1,282,412	$	1,877,264	$	1,698,853

Unit price contracts	$	377,284	$	415,404	$	985,673	$	1,006,577	$	1,359,352	$	1,316,404
Fixed price contracts	46,379		37,539		109,935		80,503		142,356		152,890
Time and materials contracts	156,729		62,307		313,090		195,332		375,556		229,559
Total Utility infrastructure services revenues	$	580,392	$	515,250	$	1,408,698	$	1,282,412	$	1,877,264	$	1,698,853

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)	September 30, 2020		December 31, 2019
Contracts receivable, net	$	275,598	$	223,904
Revenue earned on contracts in progress in excess of billings	156,754		99,399
Amounts billed in excess of revenue earned on contracts	5,522		4,525

Schedule of Construction Services Contracts Receivable

Utility infrastructure services contracts receivable consists of the following:


(Thousands of dollars)	September 30, 2020		December 31, 2019
Billed on completed contracts and contracts in progress	$	271,872	$	216,268
Other receivables	5,214		8,456
Contracts receivable, gross	277,086		224,724
Allowance for doubtful accounts	(1,488)		(820)
Contracts receivable, net	$	275,598	$	223,904

Common Stock (Tables)

9 Months Ended

Sep. 30, 2020

Equity [Abstract]

Schedule of Common Stock Activity

The following table provides the activity under the Equity Shelf Program for the three-month and life-to-date periods ended September 30, 2020:


	Three Months Ended		Life-To-Date Ended
	September 30, 2020
Gross proceeds	$	32,788,633	$	207,125,867
Less: agent commissions	(327,886)		(2,071,259)
Net proceeds	$	32,460,747	$	205,054,608
Number of shares sold	506,219		2,705,376
Weighted average price per share	$	64.77	$	76.56

Debt (Tables)

9 Months Ended

Sep. 30, 2020

Debt Disclosure [Abstract]

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


	September 30, 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	$	126,673
Notes, 6.1%, due 2041	125,000		172,353		125,000		162,666
Notes, 3.875%, due 2022	250,000		260,388		250,000		258,550
Notes, 4.875%, due 2043	250,000		317,325		250,000		291,928
Notes, 3.8%, due 2046	300,000		335,970		300,000		308,307
Notes, 3.7%, due 2028	300,000		341,388		300,000		320,685
Notes, 4.15%, due 2049	300,000		361,053		300,000		330,138
Notes, 2.2%, due 2030	450,000		471,227		—		—
8% Series, due 2026	75,000		99,423		75,000		96,905
Medium-term notes, 7.78% series, due 2022	25,000		26,944		25,000		27,500
Medium-term notes, 7.92% series, due 2027	25,000		33,716		25,000		32,543
Medium-term notes, 6.76% series, due 2027	7,500		9,569		7,500		9,156
Unamortized discount and debt issuance costs	(18,091)				(14,450)
	2,089,409				1,768,050
Revolving credit facility and commercial paper	58,000		58,000		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	(1,533)				(1,717)
	198,467				198,283
Less: current maturities	—				(125,000)
Long-term debt, less current maturities - Southwest Gas Corporation	$	2,345,876			$	1,991,333
Centuri:
Centuri term loan facility	$	231,010	$	236,477	$	244,812	$	252,182
Unamortized debt issuance costs	(890)				(1,101)
	230,120				243,711
Centuri secured revolving credit facility	59,908		59,950		60,021		60,057
Centuri other debt obligations	94,721		97,120		43,929		44,787
Less: current maturities	(44,903)				(38,512)
Long-term debt, less current maturities - Centuri	$	339,846			$	309,149
Consolidated Southwest Gas Holdings, Inc.:
Southwest Gas Corporation long-term debt	$	2,345,876			$	2,116,333
Centuri long-term debt	384,749				347,661
Less: current maturities	(44,903)				(163,512)
Long-term debt, less current maturities - Southwest Gas Holdings, Inc.	$	2,685,722			$	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.

+ References

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

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables)

9 Months Ended

Sep. 30, 2020

Equity [Abstract]


	Three Months Ended September 30, 2020						Three Months Ended September 30, 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	$	318	$	(77)	$	241
Amortization of net actuarial (gain)/loss	9,457		(2,270)		7,187		5,844		(1,402)		4,442
Regulatory adjustment	(8,394)		2,014		(6,380)		(5,348)		1,283		(4,065)
Pension plans other comprehensive income (loss)	1,352		(325)		1,027		814		(196)		618
FSIRS (designated hedging activities):
Amounts reclassified into net income	1,030		(247)		783		836		(201)		635
FSIRS other comprehensive income (loss)	1,030		(247)		783		836		(201)		635
Total other comprehensive income (loss) - Southwest Gas Corporation	2,382		(572)		1,810		1,650		(397)		1,253
Foreign currency translation adjustments:
Translation adjustments	1,024		—		1,024		(447)		—		(447)
Foreign currency other comprehensive income (loss)	1,024		—		1,024		(447)		—		(447)
Total other comprehensive income (loss) - Southwest Gas Holdings, Inc.	$	3,406	$	(572)	$	2,834	$	1,203	$	(397)	$	806

	Nine Months Ended September 30, 2020						Nine Months Ended September 30, 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	$	867	$	(208)	$	659	$	953	$	(229)	$	724
Amortization of net actuarial (gain)/loss	28,372		(6,809)		21,563		17,532		(4,207)		13,325
Regulatory adjustment	(25,184)		6,044		(19,140)		(16,043)		3,850		(12,193)
Pension plans other comprehensive income (loss)	4,055		(973)		3,082		2,442		(586)		1,856
FSIRS (designated hedging activities):
Amounts reclassified into net income	2,703		(649)		2,054		2,508		(602)		1,906
FSIRS other comprehensive income (loss)	2,703		(649)		2,054		2,508		(602)		1,906
Total other comprehensive income (loss) - Southwest Gas Corporation	6,758		(1,622)		5,136		4,950		(1,188)		3,762
Foreign currency translation adjustments:
Translation adjustments	(1,187)		—		(1,187)		1,131		—		1,131
Foreign currency other comprehensive income (loss)	(1,187)		—		(1,187)		1,131		—		1,131
Total other comprehensive income (loss) - Southwest Gas Holdings, Inc.	$	5,571	$	(1,622)	$	3,949	$	6,081	$	(1,188)	$	4,893


	Twelve Months Ended September 30, 2020						Twelve Months Ended September 30, 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	1,185		(284)		901		1,286		(309)		977
Amortization of net actuarial (gain)/loss	34,216		(8,212)		26,004		25,937		(6,224)		19,713
Prior service cost	(1,878)		452		(1,426)		—		—		—
Regulatory adjustment	27,803		(6,673)		21,130		(1,597)		383		(1,214)
Pension plans other comprehensive income (loss)	(9,761)		2,344		(7,417)		5,200		(1,248)		3,952
FSIRS (designated hedging activities):
Amounts reclassified into net income	3,539		(850)		2,689		3,344		(804)		2,540
FSIRS other comprehensive income (loss)	3,539		(850)		2,689		3,344		(804)		2,540
Total other comprehensive income (loss) - Southwest Gas Corporation	(6,222)		1,494		(4,728)		8,544		(2,052)		6,492
Foreign currency translation adjustments:
Translation adjustments	(280)		—		(280)		(877)		—		(877)
Foreign currency other comprehensive income (loss)	(280)		—		(280)		(877)		—		(877)
Total other comprehensive income (loss) - Southwest Gas Holdings, Inc.	$	(6,502)	$	1,494	$	(5,008)	$	7,667	$	(2,052)	$	5,615

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	—		—		—		—		—		—		(1,187)		—		(1,187)		(1,187)
Other comprehensive income (loss) before reclassifications	—		—		—		—		—		—		(1,187)		—		(1,187)		(1,187)
FSIRS amounts reclassified from AOCI (1)	—		—		—		2,703		(649)		2,054		—		—		—		2,054
Amortization of prior service cost (2)	867		(208)		659		—		—		—		—		—		—		659
Amortization of net actuarial loss (2)	28,372		(6,809)		21,563		—		—		—		—		—		—		21,563
Regulatory adjustment (3)	(25,184)		6,044		(19,140)		—		—		—		—		—		—		(19,140)
Net current period other comprehensive income (loss) attributable to Southwest Gas Holdings, Inc.	4,055		(973)		3,082		2,703		(649)		2,054		(1,187)		—		(1,187)		3,949
Ending Balance AOCI September 30, 2020	$	(62,546)	$	15,012	$	(47,534)	$	(3,263)	$	782	$	(2,481)	$	(2,768)	$	—	$	(2,768)	$	(52,783)

(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)	—		—		—		2,703		(649)		2,054		2,054
Amortization of prior service cost (6)	867		(208)		659		—		—		—		659
Amortization of net actuarial loss (6)	28,372		(6,809)		21,563		—		—		—		21,563
Regulatory adjustment (7)	(25,184)		6,044		(19,140)		—		—		—		(19,140)
Net current period other comprehensive income attributable to Southwest Gas Corporation	4,055		(973)		3,082		2,703		(649)		2,054		5,136
Ending Balance AOCI September 30, 2020	$	(62,546)	$	15,012	$	(47,534)	$	(3,263)	$	782	$	(2,481)	$	(50,015)

(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)	September 30, 2020		December 31, 2019
Net actuarial loss	$	(454,702)	$	(483,074)
Prior service cost	(2,774)		(3,641)
Less: amount recognized in regulatory assets	394,930		420,114
Recognized in AOCI	$	(62,546)	$	(66,601)

Segment Information (Tables)

9 Months Ended

Sep. 30, 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)	September 30, 2020		December 31, 2019
Centuri accounts receivable for services provided to Southwest	$	15,102	$	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 September 30, 2020
Revenues from external customers	$	210,834	$	548,300	$	—	$	759,134
Intersegment revenues	—		32,092		—		32,092
Total	$	210,834	$	580,392	$	—	$	791,226
Segment net income (loss)	$	(15,973)	$	34,873	$	(627)	$	18,273

Three Months Ended September 30, 2019
Revenues from external customers	$	209,980	$	480,896	$	—	$	690,876
Intersegment revenues	—		34,354		—		34,354
Total	$	209,980	$	515,250	$	—	$	725,230
Segment net income (loss)	$	(20,012)	$	25,838	$	(473)	$	5,353

(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services		Other		Total
Nine Months Ended September 30, 2020
Revenues from external customers	$	976,095	$	1,306,481	$	—	$	2,282,576
Intersegment revenues	—		102,217		—		102,217
Total	$	976,095	$	1,408,698	$	—	$	2,384,793
Segment net income (loss)	$	79,568	$	50,936	$	(1,724)	$	128,780

Nine Months Ended September 30, 2019
Revenues from external customers	$	989,368	$	1,160,303	$	—	$	2,149,671
Intersegment revenues	—		122,109		—		122,109
Total	$	989,368	$	1,282,412	$	—	$	2,271,780
Segment net income (loss)	$	86,746	$	36,725	$	(1,253)	$	122,218


(Thousands of dollars)	Natural Gas Operations		Utility Infrastructure Services		Other		Total
Twelve Months Ended September 30, 2020
Revenues from external customers	$	1,355,666	$	1,738,430	$	—	$	3,094,096
Intersegment revenues	—		138,834		—		138,834
Total	$	1,355,666	$	1,877,264	$	—	$	3,232,930
Segment net income (loss)	$	155,993	$	66,615	$	(2,110)	$	220,498

Twelve Months Ended September 30, 2019
Revenues from external customers	$	1,359,581	$	1,537,508	$	—	$	2,897,089
Intersegment revenues	—		161,345		—		161,345
Total	$	1,359,581	$	1,698,853	$	—	$	3,058,434
Segment net income (loss)	$	146,287	$	46,668	$	(1,433)	$	191,522

Background, Organization, and Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($) state instrument	Sep. 30, 2020 USD ($) state instrument	Dec. 31, 2019 USD ($)	Nov. 30, 2018
Significant Accounting Policies [Line Items]
Number of states in which entity operates \| state	3	3
Threshold period after inactivation for write-off of accounts receivable		2 months
Goodwill impairment		$ 0
Redemption value adjustments	$ 17,600,000	$ 17,573,000
Interest Rate Swap
Significant Accounting Policies [Line Items]
Derivative, Number of Instruments Held \| instrument	2	2
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	$ 55,000,000	$ 55,000,000	$ 57,000,000
Prepaid and other current assets			33,000,000
Pooled Funds and Mutual Funds
Significant Accounting Policies [Line Items]
Money market fund investments	40,000	40,000	26,700,000
Southwest Gas Corporation
Significant Accounting Policies [Line Items]
Dividends declared but not yet paid	27,000,000	27,000,000	25,200,000
Southwest Gas Corporation \| Pooled Funds and Mutual Funds
Significant Accounting Policies [Line Items]
Money market fund investments	$ 40,000	$ 40,000	$ 23,500,000

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Other Property and Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Other property	$ 22,833	$ 18,814
Total	825,069	784,173
Southwest Gas Corporation
Property, Plant and Equipment [Line Items]
Net cash surrender value of COLI policies	133,761	132,072
Other property	1,973	1,715
Total	135,734	133,787
Centuri
Property, Plant and Equipment [Line Items]
Centuri property, equipment, and intangibles	1,073,092	983,905
Centuri accumulated provision for depreciation and amortization	$ (406,590)	$ (352,333)

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 343,023
Foreign currency translation adjustment	(2,826)
Goodwill, ending balance	340,197
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	(2,826)
Goodwill, ending balance	$ 330,102

Background, Organization, and Summary of Significant Accounting Policies - Other Income (Deductions) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other income (deductions)
Total other income (deductions)	$ 1,799	$ (1,158)	$ (11,046)	$ 6,827	$ (7,788)	$ (4,448)
Southwest Gas Corporation
Other income (deductions)
Total other income (deductions)	1,751	(1,353)	(10,947)	6,185	(7,615)	(5,194)
Operating Segments \| Natural Gas Operations \| Southwest Gas Corporation
Other income (deductions)
Change in COLI policies	4,500	200	1,000	11,200	7,200	2,000
Interest income	1,412	1,521	3,214	4,940	4,630	6,659
Equity AFUDC	1,232	1,212	3,413	3,179	4,395	5,772
Other components of net periodic benefit cost	(5,005)	(3,765)	(15,016)	(11,295)	(18,780)	(16,560)
Miscellaneous income and (expense)	(388)	(521)	(3,558)	(1,839)	(5,060)	(3,065)
Total other income (deductions)	1,751	(1,353)	(10,947)	6,185	(7,615)	(5,194)
Operating Segments \| Utility Infrastructure Services \| Centuri
Other income (deductions)
Interest income	0	0	0	0	0	82
Foreign transaction gain (loss)	0	(6)	(16)	546	(16)	66
Miscellaneous income and (expense)	48	177	(91)	23	(194)	514
Total other income (deductions)	48	171	(107)	569	(210)	662
Corporate and administrative
Other income (deductions)
Total other income (deductions)	$ 0	$ 24	$ 8	$ 73	$ 37	$ 84

Background, Organization, and Summary of Significant Accounting Policies - Summary of Redeemable Noncontrolling Interest (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Movement In Redeemable Noncontrolling Interest [Roll Forward]
Redeemable noncontrolling interest, beginning balance		$ 84,542
Net income attributable to redeemable noncontrolling interest		5,169
Redemption value adjustment	$ 17,600	17,573
Redeemable noncontrolling interest, ending balance	$ 107,284	$ 107,284

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		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Weighted average basic shares (in shares)	56,271	54,670	55,683	53,996	55,508	53,219
Effect of dilutive securities:
Management Incentive Plan shares (in shares)	0	12	0	11	3	15
Restricted stock units (in shares)	86	66	70	56	66	53
Weighted average diluted shares (in shares)	56,357	54,748	55,753	54,063	55,577	53,287
Number of performance share units granted (in shares)	76	55	63	48	57	44

Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Qualified Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,576	$ 6,466	$ 25,725	$ 19,398	$ 32,191	$ 26,536
Interest cost	11,388	12,252	34,165	36,755	46,416	47,799
Expected return on plan assets	(16,324)	(15,061)	(48,972)	(45,183)	(64,033)	(59,872)
Amortization of net actuarial loss	9,006	5,589	27,019	16,767	32,608	24,796
Net periodic benefit cost	12,646	9,246	37,937	27,737	47,182	39,259
SERP
Defined Benefit Plan Disclosure [Line Items]
Service cost	97	66	292	199	359	261
Interest cost	401	440	1,204	1,320	1,644	1,734
Amortization of net actuarial loss	451	255	1,353	765	1,608	1,141
Net periodic benefit cost	949	761	2,849	2,284	3,611	3,136
PBOP
Defined Benefit Plan Disclosure [Line Items]
Service cost	395	319	1,186	957	1,505	1,325
Interest cost	646	761	1,936	2,285	2,697	2,972
Expected return on plan assets	(852)	(789)	(2,556)	(2,367)	(3,345)	(3,296)
Amortization of prior service costs	289	318	867	953	1,185	1,286
Net periodic benefit cost	$ 478	$ 609	$ 1,433	$ 1,828	$ 2,042	$ 2,287

Revenue - Additional Information (Details) $ in Millions	9 Months Ended
Revenue - Additional Information (Details) $ in Millions	Sep. 30, 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]: 2020-10-01 $ in Millions	Sep. 30, 2020 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction price allocated to unsatisfied performance obligations of contracts	$ 55.3
Transaction price allocated to unsatisfied performance obligations of contracts, period	1 year

Revenue - Schedule of Gas Operating Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 203,082	$ 200,256	$ 966,941	$ 1,005,844	$ 1,346,391	$ 1,374,724
Alternative revenue program revenues (deferrals)	9,199	7,957	9,545	(23,196)	7,629	(23,913)
Other revenues (1)	(1,447)	1,767	(391)	6,720	1,646	8,770
Total Gas operating revenues	210,834	209,980	976,095	989,368	1,355,666	1,359,581
Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	131,008	124,169	690,861	706,270	957,379	961,928
Small commercial
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	35,204	39,725	159,122	179,519	228,720	250,986
Large commercial
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9,942	10,945	32,588	36,030	45,493	49,288
Industrial/other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5,888	3,837	19,089	15,728	25,435	21,826
Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 21,040	$ 21,580	$ 65,281	$ 68,297	$ 89,364	$ 90,696

Revenue - Summary of Revenue Disaggregated by Service Type, and Contract Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 203,082	$ 200,256	$ 966,941	$ 1,005,844	$ 1,346,391	$ 1,374,724
Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	580,392	515,250	1,408,698	1,282,412	1,877,264	1,698,853
Master services agreement \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	437,914	410,283	1,076,961	1,021,798	1,438,540	1,291,397
Bid contract \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	142,478	104,967	331,737	260,614	438,724	407,456
Unit price contracts \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	377,284	415,404	985,673	1,006,577	1,359,352	1,316,404
Fixed price contracts \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	46,379	37,539	109,935	80,503	142,356	152,890
Time and materials contracts \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	156,729	62,307	313,090	195,332	375,556	229,559
Gas infrastructure services \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	387,578	364,241	935,444	885,950	1,288,468	1,160,017
Electric power infrastructure services \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	115,386	70,610	282,992	184,277	346,432	202,844
Other \| Centuri
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 77,428	$ 80,399	$ 190,262	$ 212,185	$ 242,364	$ 335,992

Revenue - Summary of Information about Receivables (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Contracts receivable, net	$ 275,598	$ 223,904
Revenue earned on contracts in progress in excess of billings	156,754	99,399
Amounts billed in excess of revenue earned on contracts	$ 5,522	$ 4,525

Revenue - Schedule of Construction Services Contracts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Billed on completed contracts and contracts in progress	$ 271,872	$ 216,268
Other receivables	5,214	8,456
Contracts receivable, gross	277,086	224,724
Allowance for doubtful accounts	(1,488)	(820)
Contracts receivable, net	$ 275,598	$ 223,904

Common Stock (Details) - USD ($)	3 Months Ended	9 Months Ended		12 Months Ended		17 Months Ended
Common Stock (Details) - USD ($)	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	May 08, 2019
Class of Stock [Line Items]
Net proceeds		$ 90,635,000	$ 129,341,000	$ 119,240,000	$ 391,509,000
Restricted Stock/Unit Plan, and Management Incentive Plan
Class of Stock [Line Items]
Common stock issued (in shares)		96,000
Dividend Reinvestment and Stock Purchase Plan
Class of Stock [Line Items]
Common stock issued (in shares)		130,000
Common stock issued, amount		$ 9,000,000
Equity Shelf Program
Class of Stock [Line Items]
Sale of stock, maximum amount of stock allowed to be offered							$ 300,000,000
Gross proceeds	$ 32,788,633					$ 207,125,867
Less: agent commissions	(327,886)					(2,071,259)
Net proceeds	$ 32,460,747					$ 205,054,608
Number of shares sold (in shares)	506,219					2,705,376
Weighted average price per share	$ 64.77					$ 76.56
Sale of common stock available for sale (in shares)	$ 92,874,133	$ 92,874,133		$ 92,874,133		$ 92,874,133

Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Less: current maturities	$ (44,903)		$ (163,512)
Long-term debt, less current maturities	2,685,722		2,300,482
Long-term Debt, Current and Noncurrent Abstract
Less: current maturities	(44,903)		(163,512)
Long-term debt, less current maturities	2,685,722		2,300,482
Southwest Gas Corporation
Debt Instrument [Line Items]
Less: current maturities	0		(125,000)
Long-term debt, less current maturities	2,345,876		1,991,333
Long-term Debt, Current and Noncurrent Abstract
Less: current maturities	0		(125,000)
Long-term debt, less current maturities	2,345,876		1,991,333
Southwest Gas Corporation \| LIBOR
Debt Instrument [Line Items]
Line of credit facility	8,000
Centuri \| LIBOR
Debt Instrument [Line Items]
Line of credit facility	$ 172,000
Debentures \| Notes, 4.45%, due 2020 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	4.45%	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 \| Notes, 2.2%, due 2030 \| Southwest Gas Corporation
Long-term Debt, Current and Noncurrent Abstract
Debt instrument interest rate	2.20%	2.20%
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	$ (44,903)		(163,512)
Long-term debt, less current maturities	2,685,722		2,300,482
Long-term Debt, Current and Noncurrent Abstract
Less: current maturities	(44,903)		(163,512)
Long-term debt, less current maturities	2,685,722		2,300,482
Carrying Amount \| Southwest Gas Corporation
Debt Instrument [Line Items]
Less: current maturities	0		(125,000)
Long-term debt, less current maturities	2,345,876		1,991,333
Long-term Debt, Current and Noncurrent Abstract
Long-term debt	2,345,876		2,116,333
Less: current maturities	0		(125,000)
Long-term debt, less current maturities	2,345,876		1,991,333
Carrying Amount \| Centuri
Debt Instrument [Line Items]
Less: current maturities	(44,903)		(38,512)
Long-term debt, less current maturities	339,846		309,149
Unamortized debt issuance costs	(890)		(1,101)
Long-term Debt, Current and Noncurrent Abstract
Long-term debt	384,749		347,661
Less: current maturities	(44,903)		(38,512)
Long-term debt, less current maturities	339,846		309,149
Centuri secured revolving credit facility	230,120		243,711
Carrying Amount \| Centuri secured revolving credit facility \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri secured revolving credit facility	59,908		60,021
Carrying Amount \| Centuri term loan facility \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri secured revolving credit facility	231,010		244,812
Carrying Amount \| Centuri other debt obligations \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri other debt obligations	94,721		43,929
Carrying Amount \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	2,089,409		1,768,050
Unamortized discount and debt issuance costs	(18,091)		(14,450)
Carrying Amount \| Debentures \| Notes, 4.45%, due 2020 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	0	$ 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 \| Notes, 2.2%, due 2030 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable	450,000		0
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	58,000		150,000
Carrying Amount \| Industrial development revenue bonds \| Southwest Gas Corporation
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(1,533)		(1,717)
Unsecured debt	198,467		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	59,950		60,057
Market Value \| Centuri term loan facility \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri secured revolving credit facility	236,477		252,182
Market Value \| Centuri other debt obligations \| Centuri
Long-term Debt, Current and Noncurrent Abstract
Centuri other debt obligations	97,120		44,787
Market Value \| Debentures \| Notes, 4.45%, due 2020 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	0		126,673
Market Value \| Debentures \| Notes, 6.1%, due 2041 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	172,353		162,666
Market Value \| Debentures \| Notes, 3.875%, due 2022 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	260,388		258,550
Market Value \| Debentures \| Notes, 4.875%, due 2043 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	317,325		291,928
Market Value \| Debentures \| Notes, 3.8%, due 2046 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	335,970		308,307
Market Value \| Debentures \| Notes, 3.7%, due 2028 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	341,388		320,685
Market Value \| Debentures \| Notes, 4.15%, due 2049 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	361,053		330,138
Market Value \| Debentures \| Notes, 2.2%, due 2030 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	471,227		0
Market Value \| Debentures \| 8% Series, due 2026 \| Southwest Gas Corporation
Debt Instrument [Line Items]
Notes payable, fair value disclosure	99,423		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	26,944		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	33,716		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	9,569		9,156
Market Value \| Debentures \| Revolving credit facility and commercial paper \| Southwest Gas Corporation
Debt Instrument [Line Items]
Line of credit facility, fair value	58,000		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 (Details)		1 Months Ended	9 Months Ended
Debt - Additional Information (Details)	Apr. 10, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Nov. 30, 2018 USD ($)	Mar. 31, 2017 USD ($)
Debt Instrument [Line Items]
Short term borrowings outstanding		$ 54,000,000	$ 54,000,000		$ 211,000,000
Percentage of total debt with interest rates reference to LIBOR and due after 2021		8.00%	8.00%
Southwest Gas Corporation
Debt Instrument [Line Items]
Short term borrowings outstanding		$ 0	$ 0		194,000,000
Percentage of total debt with interest rates reference to LIBOR and due after 2021		0.30%	0.30%
Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt		$ 2,345,876,000	$ 2,345,876,000		2,116,333,000
Southwest Gas Corporation \| Debentures \| Carrying Amount
Debt Instrument [Line Items]
Notes payable		2,089,409,000	2,089,409,000		1,768,050,000
Southwest Gas Corporation \| Commercial Paper Program
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity		50,000,000	50,000,000
Borrowings outstanding under facility		$ 50,000,000	$ 50,000,000
Southwest Gas Corporation \| Notes, 2.2%, due 2030 \| Debentures
Debt Instrument [Line Items]
Debt instrument, face amount				$ 450,000,000
Debt instrument interest rate		2.20%	2.20%	2.20%
Debt instrument discount rate				0.126%
Southwest Gas Corporation \| Notes, 2.2%, due 2030 \| Debentures \| Carrying Amount
Debt Instrument [Line Items]
Notes payable		$ 450,000,000	$ 450,000,000		0
Southwest Gas Corporation \| Notes, 4.45%, due 2020 \| Debentures
Debt Instrument [Line Items]
Debt instrument interest rate		4.45%	4.45%	4.45%
Debt redemption price, percentage		100.00%
Southwest Gas Corporation \| Notes, 4.45%, due 2020 \| Debentures \| Carrying Amount
Debt Instrument [Line Items]
Notes payable		$ 0	$ 0	$ 125,000,000	125,000,000
Centuri \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt		384,749,000	384,749,000		$ 347,661,000
Centuri \| Secured Revolving Credit Facility and Term Loan
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity						$ 590,000,000
Borrowings outstanding under facility		291,000,000	291,000,000
Debt secured by assets		1,400,000,000	1,400,000,000
Centuri \| Line of Credit
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity						325,000,000
Centuri \| Centuri term loan facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity						$ 265,000,000
Centuri \| Equipment Loans
Debt Instrument [Line Items]
Proceeds from debt			70,000,000
LIBOR \| Southwest Gas Holdings
Debt Instrument [Line Items]
Borrowings outstanding under facility		54,000,000	54,000,000
LIBOR \| Southwest Gas Corporation
Debt Instrument [Line Items]
Borrowings outstanding under facility		8,000,000	8,000,000
LIBOR \| Centuri
Debt Instrument [Line Items]
Borrowings outstanding under facility		172,000,000	172,000,000
$400 Million Credit Facility \| Minimum
Debt Instrument [Line Items]
Commitment fee percentage	0.075%
$400 Million Credit Facility \| Maximum
Debt Instrument [Line Items]
Commitment fee percentage	0.20%
$400 Million Credit Facility \| Southwest Gas Corporation
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity	$ 400,000,000	400,000,000	400,000,000
Line of credit designated as long term debt		150,000,000	150,000,000
Line of credit designated for working capital purposes		250,000,000	250,000,000
Long-term debt		58,000,000	58,000,000
Debt covenant, ratio of funded debt to total capitalization	0.70
Short term borrowings outstanding		$ 0	$ 0
$400 Million Credit Facility \| LIBOR \| Minimum
Debt Instrument [Line Items]
Applicable margin	0.75%
$400 Million Credit Facility \| LIBOR \| Maximum
Debt Instrument [Line Items]
Applicable margin	1.50%
$400 Million Credit Facility \| LIBOR \| Southwest Gas Corporation
Debt Instrument [Line Items]
Applicable margin			1.00%
$400 Million Credit Facility \| Alternative base rate \| Minimum
Debt Instrument [Line Items]
Applicable margin	0.00%
$400 Million Credit Facility \| Alternative base rate \| Maximum
Debt Instrument [Line Items]
Applicable margin	0.50%
$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						$ 100,000,000

Other Comprehensive Income and Accumulated Other Comprehensive Income - Related Tax Effects Allocated to OCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, net of tax			$ (1,187)
Other comprehensive income (loss), before tax	$ 3,406	$ 1,203	5,571	$ 6,081	$ (6,502)	$ 7,667
Other comprehensive income (loss), tax	(572)	(397)	(1,622)	(1,188)	1,494	(2,052)
Total other comprehensive income (loss), net of tax	2,834	806	$ 3,949	4,893	$ (5,008)	5,615
Effective income tax rate			24.00%		24.00%
Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	2,382	1,650	$ 6,758	4,950	$ (6,222)	8,544
Other comprehensive income (loss), tax	(572)	(397)	(1,622)	(1,188)	1,494	(2,052)
Total other comprehensive income (loss), net of tax	1,810	1,253	5,136	3,762	(4,728)	6,492
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	1,352	814	4,055	2,442	(9,761)	5,200
Other comprehensive income (loss), tax	(325)	(196)	(973)	(586)	2,344	(1,248)
Total other comprehensive income (loss), net of tax	1,027	618	3,082	1,856	(7,417)	3,952
Defined Benefit Plans \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax			4,055
Other comprehensive income (loss), tax			(973)
Total other comprehensive income (loss), net of tax			3,082
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	9,457	5,844	28,372	17,532	34,216	25,937
Reclassification from AOCI, tax	(2,270)	(1,402)	(6,809)	(4,207)	(8,212)	(6,224)
Reclassification from AOCI, net of tax	7,187	4,442	21,563	13,325	26,004	19,713
Other comprehensive income (loss), before tax			28,372
Other comprehensive income (loss), tax			(6,809)
Total other comprehensive income (loss), net of tax			21,563
Net actuarial gain/(loss) \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax			28,372
Other comprehensive income (loss), tax			(6,809)
Total other comprehensive income (loss), net of tax			21,563
Amortization of prior service cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	289	318	867	953	1,185	1,286
Reclassification from AOCI, tax	(69)	(77)	(208)	(229)	(284)	(309)
Reclassification from AOCI, net of tax	220	241	659	724	901	977
Other comprehensive income (loss), before tax			867
Other comprehensive income (loss), tax			(208)
Total other comprehensive income (loss), net of tax			659
Amortization of prior service cost \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax			867
Other comprehensive income (loss), tax			(208)
Total other comprehensive income (loss), net of tax			659
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	(8,394)	(5,348)	(25,184)	(16,043)	27,803	(1,597)
Reclassification from AOCI, tax	2,014	1,283	6,044	3,850	(6,673)	383
Reclassification from AOCI, net of tax	(6,380)	(4,065)	(19,140)	(12,193)	21,130	(1,214)
Other comprehensive income (loss), before tax			(25,184)
Other comprehensive income (loss), tax			6,044
Total other comprehensive income (loss), net of tax			(19,140)
Regulatory adjustment \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax			(25,184)
Other comprehensive income (loss), tax			6,044
Total other comprehensive income (loss), net of tax			(19,140)
FSIRS
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	1,030	836	2,703	2,508	3,539	3,344
Reclassification from AOCI, tax	(247)	(201)	(649)	(602)	(850)	(804)
Reclassification from AOCI, net of tax	783	635	2,054	1,906	2,689	2,540
Other comprehensive income (loss), before tax	1,030	836	2,703	2,508	3,539	3,344
Other comprehensive income (loss), tax	(247)	(201)	(649)	(602)	(850)	(804)
Total other comprehensive income (loss), net of tax	783	635	2,054	1,906	2,689	2,540
FSIRS \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax			2,703
Reclassification from AOCI, tax			(649)
Reclassification from AOCI, net of tax			2,054
Other comprehensive income (loss), before tax			2,703
Other comprehensive income (loss), tax			(649)
Total other comprehensive income (loss), net of tax			2,054
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax	1,024	(447)	(1,187)	1,131	(280)	(877)
Other comprehensive income (loss) before reclassifications, tax	0	0	0	0	0	0
Other comprehensive income (loss) before reclassifications, net of tax	$ 1,024	$ (447)	(1,187)	$ 1,131	$ (280)	$ (877)
Other comprehensive income (loss), before tax			(1,187)
Total other comprehensive income (loss), net of tax			$ (1,187)

Other Comprehensive Income and Accumulated Other Comprehensive Income - Additional Information (Details) $ in Millions	Sep. 30, 2020 USD ($)
Equity [Abstract]
Amount of FSIRS existing AOCI losses expected to reclassified income in next twelve months	$ 1.7

Other Comprehensive Income and Accumulated Other Comprehensive Income - AOCI Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance					$ 2,423,710
Beginning balance, attributable to parent			$ 2,505,914
Other comprehensive income (loss) before reclassifications, net of tax			(1,187)
Other comprehensive income (loss), before tax	$ 3,406	$ 1,203	5,571	$ 6,081	(6,502)	$ 7,667
Other comprehensive income (loss), tax	(572)	(397)	(1,622)	(1,188)	1,494	(2,052)
Total other comprehensive income (loss), net of tax	2,834	806	3,949	4,893	(5,008)	5,615
Ending balance, attributable to parent	2,619,238		2,619,238		2,619,238
Ending balance	2,619,238	2,423,710	$ 2,619,238	2,423,710	$ 2,619,238	2,423,710
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	4,055	2,442	$ (9,761)	5,200
Other comprehensive income (loss), tax	(325)	(196)	(973)	(586)	2,344	(1,248)
Total other comprehensive income (loss), net of tax	1,027	618	3,082	1,856	(7,417)	3,952
Ending balance, before tax	(62,546)		(62,546)		(62,546)
Ending balance, tax	15,012		15,012		15,012
Ending balance	(47,534)		(47,534)		(47,534)
Amortization of prior service cost
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, before Tax	289	318	867	953	1,185	1,286
Reclassification from AOCI, tax	(69)	(77)	(208)	(229)	(284)	(309)
Reclassification from AOCI, net of tax	220	241	659	724	901	977
Other comprehensive income (loss), before tax			867
Other comprehensive income (loss), tax			(208)
Total other comprehensive income (loss), net of tax			659
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	9,457	5,844	28,372	17,532	34,216	25,937
Reclassification from AOCI, tax	(2,270)	(1,402)	(6,809)	(4,207)	(8,212)	(6,224)
Reclassification from AOCI, net of tax	7,187	4,442	21,563	13,325	26,004	19,713
Other comprehensive income (loss), before tax			28,372
Other comprehensive income (loss), tax			(6,809)
Total other comprehensive income (loss), net of tax			21,563
Regulatory adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, before Tax	(8,394)	(5,348)	(25,184)	(16,043)	27,803	(1,597)
Reclassification from AOCI, tax	2,014	1,283	6,044	3,850	(6,673)	383
Reclassification from AOCI, net of tax	(6,380)	(4,065)	(19,140)	(12,193)	21,130	(1,214)
Other comprehensive income (loss), before tax			(25,184)
Other comprehensive income (loss), tax			6,044
Total other comprehensive income (loss), net of tax			(19,140)
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	1,030	836	2,703	2,508	3,539	3,344
Reclassification from AOCI, tax	(247)	(201)	(649)	(602)	(850)	(804)
Reclassification from AOCI, net of tax	783	635	2,054	1,906	2,689	2,540
Other comprehensive income (loss), before tax	1,030	836	2,703	2,508	3,539	3,344
Other comprehensive income (loss), tax	(247)	(201)	(649)	(602)	(850)	(804)
Total other comprehensive income (loss), net of tax	783	635	2,054	1,906	2,689	2,540
Ending balance, before tax	(3,263)		(3,263)		(3,263)
Ending balance, tax	782		782		782
Ending balance	(2,481)		(2,481)		(2,481)
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	1,024	(447)	(1,187)	1,131	(280)	(877)
Other comprehensive income (loss) before reclassifications, net of tax	1,024	(447)	(1,187)	1,131	(280)	(877)
Other comprehensive income (loss), before tax			(1,187)
Total other comprehensive income (loss), net of tax			(1,187)
Ending balance, before tax	(2,768)		(2,768)		(2,768)
Ending balance	(2,768)		(2,768)		(2,768)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(55,617)	(48,581)	(56,732)	(52,668)	(47,775)
Ending balance	(52,783)	(47,775)	(52,783)	(47,775)	(52,783)	(47,775)
Southwest Gas Corporation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance					1,929,606
Beginning balance, attributable to parent			2,005,152
Other comprehensive income (loss), before tax	2,382	1,650	6,758	4,950	(6,222)	8,544
Other comprehensive income (loss), tax	(572)	(397)	(1,622)	(1,188)	1,494	(2,052)
Total other comprehensive income (loss), net of tax	1,810	1,253	5,136	3,762	(4,728)	6,492
Ending balance, attributable to parent	2,144,273		2,144,273		2,144,273
Ending balance	2,144,273	1,929,606	2,144,273	1,929,606	2,144,273	1,929,606
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			4,055
Other comprehensive income (loss), tax			(973)
Total other comprehensive income (loss), net of tax			3,082
Ending balance, attributable to parent, before tax	(62,546)		(62,546)		(62,546)
Ending balance, attributable to parent, tax	15,012		15,012		15,012
Ending balance, attributable to parent	(47,534)		(47,534)		(47,534)
Southwest Gas Corporation \| Amortization of prior service cost
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before tax			867
Other comprehensive income (loss), tax			(208)
Total other comprehensive income (loss), net of tax			659
Southwest Gas Corporation \| Amortization of net actuarial loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before tax			28,372
Other comprehensive income (loss), tax			(6,809)
Total other comprehensive income (loss), net of tax			21,563
Southwest Gas Corporation \| Regulatory adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before tax			(25,184)
Other comprehensive income (loss), tax			6,044
Total other comprehensive income (loss), net of tax			(19,140)
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			2,703
Reclassification from AOCI, tax			(649)
Reclassification from AOCI, net of tax			2,054
Other comprehensive income (loss), before tax			2,703
Other comprehensive income (loss), tax			(649)
Total other comprehensive income (loss), net of tax			2,054
Ending balance, attributable to parent, before tax	(3,263)		(3,263)		(3,263)
Ending balance, attributable to parent, tax	782		782		782
Ending balance, attributable to parent	(2,481)		(2,481)		(2,481)
Southwest Gas Corporation \| AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(51,825)	(46,540)	(55,151)	(49,049)	(45,287)
Beginning balance, attributable to parent			(55,151)
Ending balance, attributable to parent	(50,015)		(50,015)		(50,015)
Ending balance	$ (50,015)	$ (45,287)	$ (50,015)	$ (45,287)	$ (50,015)	$ (45,287)

Other Comprehensive Income and Accumulated Other Comprehensive Income - Amounts Recognized Before Tax, Defined Benefit Plans (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Equity [Abstract]
Net actuarial loss	$ (454,702)	$ (483,074)
Prior service cost	(2,774)	(3,641)
Less: amount recognized in regulatory assets	394,930	420,114
Recognized in AOCI	$ (62,546)	$ (66,601)

Segment Information - Accounts Receivable for Services (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Centuri
Segment Reporting Information [Line Items]
Centuri accounts receivable for services provided to Southwest	$ 15,102	$ 15,235

Segment Information - Additional Information (Details)	9 Months Ended
Segment Information - Additional Information (Details)	Sep. 30, 2020 Segment
Segment Reporting [Abstract]
Number of reportable segments	2

Segment Information - Schedule of Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 791,226	$ 725,230	$ 2,384,793	$ 2,271,780		$ 3,232,930		$ 3,058,434
Segment net income (loss)	18,273	5,353	128,780	122,218	$ 220,498	220,498	$ 191,522	191,522
Operating Segments
Segment Reporting Information [Line Items]
Revenues	759,134	690,876	2,282,576	2,149,671		3,094,096		2,897,089
Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenues	(32,092)	(34,354)	(102,217)	(122,109)		(138,834)		(161,345)
Segment net income (loss)	(627)	(473)	(1,724)	(1,253)		(2,110)		(1,433)
Natural Gas Operations
Segment Reporting Information [Line Items]
Revenues	210,834	209,980	976,095	989,368		1,355,666		1,359,581
Segment net income (loss)	(15,973)	(20,012)	79,568	86,746		155,993		146,287
Natural Gas Operations \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	210,834	209,980	976,095	989,368		1,355,666		1,359,581
Natural Gas Operations \| Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenues	0	0	0	0		0		0
Utility Infrastructure Services
Segment Reporting Information [Line Items]
Revenues	580,392	515,250	1,408,698	1,282,412		1,877,264		1,698,853
Segment net income (loss)	34,873	25,838	50,936	36,725		66,615		46,668
Utility Infrastructure Services \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	548,300	480,896	1,306,481	1,160,303		1,738,430		1,537,508
Utility Infrastructure Services \| Segment Reconciling Items
Segment Reporting Information [Line Items]
Revenues	$ (32,092)	$ (34,354)	$ (102,217)	$ (122,109)		$ (138,834)		$ (161,345)

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669619-108580

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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