Southwest Gas (SWX) 10-Q6 Nov 242024 Q3 Quarterly reportFinancial data

Company Profile

Cover

Cover - shares	9 Months Ended
Cover - shares	Sep. 30, 2024	Oct. 25, 2024
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
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, City or Town	Las Vegas,
Entity Address, State or Province	NV
Entity Address, Postal Zip Code	89113
City Area Code	(702)
Local Phone Number	876-7237
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		71,743,666
Entity Central Index Key	0001692115
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Southwest Gas Holdings, Inc. Common Stock, $1 Par Value
Entity Information [Line Items]
Title of 12(b) Security	Southwest Gas Holdings, Inc. Common Stock, $1 Par Value
Trading Symbol	SWX
Security Exchange Name	NYSE
Preferred Stock Purchase Rights
Entity Information [Line Items]
Title of 12(b) Security	Preferred Stock Purchase Rights
Security Exchange Name	NYSE
No Trading Symbol - Preferred Stock Purchase Rights	true
Southwest Gas Corporation
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
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, City or Town	Las Vegas,
Entity Address, State or Province	NV
Entity Address, Postal Zip Code	89113
City Area Code	(702)
Local Phone Number	876-7237
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0000092416
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Amendment Flag	false
Current Fiscal Year End Date	--12-31

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Regulated operations plant:
Gas plant	$ 10,652,224	$ 10,140,362
Less: accumulated depreciation	(2,937,435)	(2,822,669)
Construction work in progress	243,375	200,549
Net regulated operations plant	7,958,164	7,518,242
Other property and investments, net	1,193,062	1,266,340
Current assets:
Cash and cash equivalents	456,643	106,536
Accounts receivable, net of allowance	673,219	886,549
Accrued utility revenue	47,800	93,000
Income taxes receivable, net	7,401	1,935
Deferred purchased gas costs	9,270	552,885
Prepaid and other current assets	261,063	218,832
Current assets held for sale	0	21,377
Total current assets	1,455,396	1,881,114
Noncurrent assets:
Goodwill	787,595	789,729
Deferred income taxes	2,833	463
Deferred charges and other assets	477,900	414,008
Total noncurrent assets	1,268,328	1,204,200
Total assets	11,874,950	11,869,896
Capitalization:
Common stock, $1 par (authorized - 120,000,000 shares; issued and outstanding - 71,740,332 and 71,563,750 shares)	73,370	73,194
Additional paid-in capital	2,714,958	2,541,790
Accumulated other comprehensive loss, net	(43,875)	(43,787)
Retained earnings	710,940	738,839
Total equity	3,455,393	3,310,036
Noncontrolling interest	176,857	0
Total equity	3,632,250	3,310,036
Redeemable noncontrolling interest	7,706	104,667
Long-term debt, less current maturities	4,382,146	4,609,838
Total capitalization	8,022,102	8,024,541
Current liabilities:
Current maturities of long-term debt	30,264	42,552
Short-term debt	663,000	628,500
Accounts payable	226,960	346,907
Customer deposits	60,750	48,460
Income taxes payable, net	2,019	817
Accrued general taxes	64,005	58,053
Accrued interest	44,514	36,605
Deferred purchased gas costs	188,985	0
Other current liabilities	422,245	522,953
Total current liabilities	1,702,742	1,684,847
Deferred income taxes and other credits:
Deferred income taxes and investment tax credits, net	790,825	752,997
Accumulated removal costs	465,000	458,000
Other deferred credits and other long-term liabilities	894,281	949,511
Total deferred income taxes and other credits	2,150,106	2,160,508
Total capitalization and liabilities	$ 11,874,950	$ 11,869,896

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2024	Dec. 31, 2023
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)	71,740,332	71,563,750
Common stock, outstanding (in shares)	71,740,332	71,563,750

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Operating revenues:
Regulated operations revenues	$ 359,131	$ 394,603	$ 1,922,157	$ 1,832,480
Utility infrastructure services revenues	720,053	774,889	1,920,151	2,233,961
Total operating revenues	1,079,184	1,169,492	3,842,308	4,066,441
Operating expenses:
Net cost of gas sold	111,712	170,056	984,188	908,646
Operations and maintenance	131,416	126,851	401,185	404,554
Depreciation and amortization	107,361	105,520	322,575	329,745
Taxes other than income taxes	22,283	21,147	66,414	66,981
Utility infrastructure services expenses	644,928	685,687	1,765,116	2,005,084
Goodwill impairment and loss on sale	0	0	0	71,230
Total operating expenses	1,017,700	1,109,261	3,539,478	3,786,240
Operating income	61,484	60,231	302,830	280,201
Other income and (expenses):
Net interest deductions	(77,731)	(71,998)	(223,105)	(218,679)
Other income	16,758	14,464	49,818	52,528
Total other income and (expenses)	(60,973)	(57,534)	(173,287)	(166,151)
Income before income taxes	511	2,697	129,543	114,050
Income tax expense (benefit)	(2,152)	(1,270)	19,108	32,174
Net income	2,663	3,967	110,435	81,876
Net income attributable to noncontrolling interests	2,374	736	4,076	3,856
Net income attributable to Southwest Gas Holdings, Inc.	$ 289	$ 3,231	$ 106,359	$ 78,020
Earnings per share attributable to Southwest Gas Holdings, Inc.:
Basic (in USD per share)	$ 0	$ 0.05	$ 1.48	$ 1.11
Diluted (in USD per share)	$ 0	$ 0.04	$ 1.48	$ 1.10
Weighted average shares:
Basic (in shares)	71,880	71,626	71,816	70,488
Diluted (in shares)	72,086	71,851	71,994	70,676

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 2,663	$ 3,967	$ 110,435	$ 81,876
Defined benefit pension plans:
Amortization of prior service cost	33	33	99	99
Amortization of net actuarial loss	1,452	253	4,355	760
Regulatory adjustment	(1,101)	(90)	(3,300)	(270)
Net defined benefit pension plans	384	196	1,154	589
Foreign currency translation adjustments	1,675	(2,261)	(2,296)	130
Total other comprehensive income (loss), net of tax	2,059	(2,065)	(1,142)	719
Comprehensive income	4,722	1,902	109,293	82,595
Comprehensive income attributable to noncontrolling interests	2,693	736	4,226	3,856
Comprehensive income attributable to Southwest Gas Holdings, Inc.	$ 2,029	$ 1,166	$ 105,067	$ 78,739

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	$ 110,435	$ 81,876
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	322,575	329,745
Impairment of assets and other charges	0	71,230
Deferred income taxes	35,263	45,317
Gains on sale of property and equipment	(2,651)	(3,090)
Changes in undistributed stock compensation	10,020	8,557
Equity AFUDC	(5,548)	(82)
Changes in current assets and liabilities:
Accounts receivable, net of allowances	187,099	(40,232)
Accrued utility revenue	45,200	43,500
Deferred purchased gas costs	732,600	(252,022)
Accounts payable	(99,763)	(360,554)
Accrued taxes	1,690	12,687
Other current assets and liabilities	(143,233)	315,728
Changes in deferred charges and other assets	(16,582)	1,243
Changes in other liabilities and deferred credits	(22,769)	(55,469)
Net cash provided by operating activities	1,154,336	198,434
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(709,813)	(664,590)
Proceeds from the sale of business, net of cash sold	0	1,022,483
Proceeds from the sale of property	21,377	0
Changes in customer advances	(4,804)	(6,974)
Other	5,918	6,147
Net cash provided by (used in) investing activities	(687,322)	357,066
CASH FLOW FROM FINANCING ACTIVITIES:
Issuance of common stock, net	6,681	249,238
Redemption of redeemable noncontrolling interest	(92,839)	(39,894)
Dividends paid	(133,285)	(130,232)
Issuance of long-term debt, net	280,408	1,043,602
Retirement of long-term debt	(525,511)	(168,127)
Change in short-term portion of credit facility	34,500	(115,000)
Change in long-term credit facility and commercial paper	0	(50,000)
Issuance of short-term debt	0	450,000
Repayment of short-term debt	0	(1,822,747)
Withholding remittance - share-based compensation	(2,476)	(1,742)
Proceeds from Centuri initial public offering, net	327,967	0
Other, including principal payments on finance leases	(12,210)	(12,642)
Net cash used in financing activities	(116,765)	(597,544)
Effects of currency translation on cash and cash equivalents	(142)	102
Change in cash and cash equivalents	350,107	(41,942)
Cash and cash equivalents included in current assets held for sale at beginning of period			$ 0	$ 23,803
Cash and cash equivalents at beginning of period	106,536	123,078
Cash and cash equivalents at end of period	456,643	104,939
SUPPLEMENTAL INFORMATION:
Interest paid, net of amounts capitalized	204,135	196,609
Income taxes paid, net	$ 8,108	$ 5,957

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Parent	Common stock shares	Additional paid-in capital	Additional paid-in capital IPO	Accumulated other comprehensive loss	Retained earnings	Noncontrolling interest	Noncontrolling interest IPO
Beginning balance (in shares) at Dec. 31, 2022			67,119,000
Beginning balance at Dec. 31, 2022			$ 68,749	$ 2,287,183		$ (44,242)	$ 747,069	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)			4,396,000
Common stock issuances and Centuri IPO			$ 4,396	252,576
Foreign currency exchange translation adjustment						130
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax						589
Net income							78,020
Dividends declared							(133,879)
Redemption value adjustments							(21,846)
Ending balance (in shares) at Sep. 30, 2023			71,515,000
Ending balance at Sep. 30, 2023	$ 3,238,745	$ 3,238,745	$ 73,145	2,539,759		(43,523)	669,364	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in USD per share)	$ 1.86
Beginning balance (in shares) at Jun. 30, 2023			71,473,000
Beginning balance at Jun. 30, 2023			$ 73,103	2,534,223		(41,458)	696,958	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)			42,000
Common stock issuances and Centuri IPO			$ 42	5,536
Foreign currency exchange translation adjustment						(2,261)
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax						196
Net income							3,231
Dividends declared							(44,584)
Redemption value adjustments							13,759
Ending balance (in shares) at Sep. 30, 2023			71,515,000
Ending balance at Sep. 30, 2023	$ 3,238,745	3,238,745	$ 73,145	2,539,759		(43,523)	669,364	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in USD per share)	$ 0.62
Beginning balance (in shares) at Dec. 31, 2023	71,563,750		71,564,000
Beginning balance at Dec. 31, 2023	$ 3,310,036		$ 73,194	2,541,790		(43,787)	738,839	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)			176,000
Common stock issuances and Centuri IPO			$ 176	14,694	$ 154,287	1,204			$ 172,501
Promissory notes in association with redeemable noncontrolling interest				4,187
Foreign currency exchange translation adjustment						(2,446)		150
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax						1,154
Net income							106,359	4,206
Dividends declared							(134,064)
Redemption value adjustments	$ 194						(194)
Ending balance (in shares) at Sep. 30, 2024	71,740,332		71,740,000
Ending balance at Sep. 30, 2024	$ 3,632,250	3,455,393	$ 73,370	2,714,958		(43,875)	710,940	176,857
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in USD per share)	$ 1.86
Beginning balance (in shares) at Jun. 30, 2024			71,709,000
Beginning balance at Jun. 30, 2024			$ 73,339	2,709,674		(45,615)	755,367	174,199
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)			31,000
Common stock issuances and Centuri IPO			$ 31	5,284
Foreign currency exchange translation adjustment						1,356		319
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax						384
Net income							289	2,339
Dividends declared							(44,716)
Ending balance (in shares) at Sep. 30, 2024	71,740,332		71,740,000
Ending balance at Sep. 30, 2024	$ 3,632,250	$ 3,455,393	$ 73,370	$ 2,714,958		$ (43,875)	$ 710,940	$ 176,857
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in USD per share)	$ 0.62

CONDENSED CONSOLIDATED BALANC_3

CONDENSED CONSOLIDATED BALANCE SHEETS - Southwest - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Regulated operations plant:
Gas plant	$ 10,652,224	$ 10,140,362
Less: accumulated depreciation	(2,937,435)	(2,822,669)
Construction work in progress	243,375	200,549
Net regulated operations plant	7,958,164	7,518,242
Other property and investments, net	1,193,062	1,266,340
Current assets:
Cash and cash equivalents	456,643	106,536
Accounts receivable, net of allowance	673,219	886,549
Accrued utility revenue	47,800	93,000
Income taxes receivable, net	7,401	1,935
Deferred purchased gas costs	9,270	552,885
Prepaid and other current assets	261,063	218,832
Current assets held for sale	0	21,377
Total current assets	1,455,396	1,881,114
Noncurrent assets:
Goodwill	787,595	789,729
Deferred charges and other assets	477,900	414,008
Total noncurrent assets	1,268,328	1,204,200
Total assets	11,874,950	11,869,896
Capitalization:
Common stock	73,370	73,194
Additional paid-in capital	2,714,958	2,541,790
Accumulated other comprehensive loss, net	(43,875)	(43,787)
Retained earnings	710,940	738,839
Total equity	3,455,393	3,310,036
Long-term debt, less current maturities	4,382,146	4,609,838
Total capitalization	8,022,102	8,024,541
Current liabilities:
Accounts payable	226,960	346,907
Customer deposits	60,750	48,460
Accrued general taxes	64,005	58,053
Accrued interest	44,514	36,605
Deferred purchased gas costs	188,985	0
Other current liabilities	422,245	522,953
Total current liabilities	1,702,742	1,684,847
Deferred income taxes and other credits:
Deferred income taxes and investment tax credits, net	790,825	752,997
Accumulated removal costs	465,000	458,000
Other deferred credits and other long-term liabilities	894,281	949,511
Total deferred income taxes and other credits	2,150,106	2,160,508
Total capitalization and liabilities	11,874,950	11,869,896
Southwest Gas Corporation
Regulated operations plant:
Gas plant	10,652,224	10,140,362
Less: accumulated depreciation	(2,937,435)	(2,822,669)
Construction work in progress	243,375	200,549
Net regulated operations plant	7,958,164	7,518,242
Other property and investments, net	159,174	152,658
Current assets:
Cash and cash equivalents	401,653	71,154
Accrued utility revenue	47,800	93,000
Income taxes receivable, net	43	26
Deferred purchased gas costs	9,270	552,885
Prepaid and other current assets	222,148	188,138
Current assets held for sale	0	21,376
Total current assets	812,474	1,195,774
Noncurrent assets:
Goodwill	11,155	11,155
Deferred charges and other assets	400,762	390,742
Total noncurrent assets	411,917	401,897
Total assets	9,341,729	9,268,571
Capitalization:
Common stock	49,112	49,112
Additional paid-in capital	2,162,196	2,156,577
Accumulated other comprehensive loss, net	(39,394)	(40,548)
Retained earnings	1,043,648	1,018,474
Total equity	3,215,562	3,183,615
Long-term debt, less current maturities	3,503,629	3,501,543
Total capitalization	6,719,191	6,685,158
Current liabilities:
Customer deposits	60,750	48,460
Accrued general taxes	64,005	58,053
Accrued interest	38,363	34,955
Deferred purchased gas costs	188,985	0
Other current liabilities	204,254	271,899
Total current liabilities	651,808	630,822
Deferred income taxes and other credits:
Deferred income taxes and investment tax credits, net	797,262	749,836
Accumulated removal costs	465,000	458,000
Other deferred credits and other long-term liabilities	708,468	744,755
Total deferred income taxes and other credits	1,970,730	1,952,591
Total capitalization and liabilities	9,341,729	9,268,571
Southwest Gas Corporation \| Nonrelated Party
Current assets:
Accounts receivable, net of allowance	131,560	269,195
Current liabilities:
Accounts payable	95,036	215,744
Southwest Gas Corporation \| Related Party
Current liabilities:
Accounts payable	$ 415	$ 1,711

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - Southwest - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Regulated operations revenues	$ 1,079,184	$ 1,169,492	$ 3,842,308	$ 4,066,441
Operating expenses:
Net cost of gas sold	111,712	170,056	984,188	908,646
Operations and maintenance	131,416	126,851	401,185	404,554
Depreciation and amortization	107,361	105,520	322,575	329,745
Taxes other than income taxes	22,283	21,147	66,414	66,981
Total operating expenses	1,017,700	1,109,261	3,539,478	3,786,240
Operating income	61,484	60,231	302,830	280,201
Other income and (expenses):
Net interest deductions	(77,731)	(71,998)	(223,105)	(218,679)
Other income	16,758	14,464	49,818	52,528
Total other income and (expenses)	(60,973)	(57,534)	(173,287)	(166,151)
Income before income taxes	511	2,697	129,543	114,050
Income tax expense (benefit)	(2,152)	(1,270)	19,108	32,174
Net income attributable to Southwest Gas Holdings, Inc.	289	3,231	106,359	78,020
Southwest Gas Corporation
Regulated operations revenues	359,131	394,603	1,922,157	1,797,348
Operating expenses:
Net cost of gas sold	111,712	170,056	984,188	902,278
Operations and maintenance	129,736	122,270	390,229	378,189
Depreciation and amortization	74,153	69,268	220,663	218,763
Taxes other than income taxes	22,283	21,147	66,414	65,491
Total operating expenses	337,884	382,741	1,661,494	1,564,721
Operating income	21,247	11,862	260,663	232,627
Other income and (expenses):
Net interest deductions	(42,312)	(35,772)	(118,595)	(111,498)
Other income	16,665	14,537	48,976	51,722
Total other income and (expenses)	(25,647)	(21,235)	(69,619)	(59,776)
Income before income taxes	(4,400)	(9,373)	191,044	172,851
Income tax expense (benefit)	(4,972)	(6,122)	27,053	22,286
Net income attributable to Southwest Gas Holdings, Inc.	$ 572	$ (3,251)	$ 163,991	$ 150,565

CONDENSED CONSOLIDATED STATEM_6

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - Southwest - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Net income	$ 2,663	$ 3,967	$ 110,435	$ 81,876
Defined benefit pension plans:
Amortization of prior service cost	33	33	99	99
Amortization of net actuarial loss	1,452	253	4,355	760
Regulatory adjustment	(1,101)	(90)	(3,300)	(270)
Net defined benefit pension plans	384	196	1,154	589
Total other comprehensive income (loss), net of tax	2,059	(2,065)	(1,142)	719
Comprehensive income	4,722	1,902	109,293	82,595
Southwest Gas Corporation
Net income	572	(3,251)	163,991	150,565
Defined benefit pension plans:
Amortization of prior service cost	33	33	99	99
Amortization of net actuarial loss	1,452	253	4,355	760
Regulatory adjustment	(1,101)	(90)	(3,300)	(270)
Net defined benefit pension plans	384	196	1,154	589
Total other comprehensive income (loss), net of tax	384	196	1,154	589
Comprehensive income	$ 956	$ (3,055)	$ 165,145	$ 151,154

CONDENSED CONSOLIDATED STATEM_7

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - Southwest - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	$ 110,435	$ 81,876
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	322,575	329,745
Deferred income taxes	35,263	45,317
Gains on sale of property and equipment	(2,651)	(3,090)
Changes in undistributed stock compensation	10,020	8,557
Equity AFUDC	(5,548)	(82)
Changes in current assets and liabilities:
Accounts receivable, net of allowance	187,099	(40,232)
Accrued utility revenue	45,200	43,500
Deferred purchased gas costs	732,600	(252,022)
Accounts payable	(99,763)	(360,554)
Accrued taxes	1,690	12,687
Other current assets and liabilities	(143,233)	315,728
Changes in deferred charges and other assets	(16,582)	1,243
Changes in other liabilities and deferred credits	(22,769)	(55,469)
Net cash provided by operating activities	1,154,336	198,434
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(709,813)	(664,590)
Proceeds from the sale of property	21,377	0
Changes in customer advances	(4,804)	(6,974)
Other	5,918	6,147
Net cash provided by (used in) investing activities	(687,322)	357,066
CASH FLOW FROM FINANCING ACTIVITIES:
Dividends paid	(133,285)	(130,232)
Issuance of long-term debt, net	280,408	1,043,602
Change in long-term credit facility and commercial paper	0	(50,000)
Issuance of short-term debt	0	450,000
Repayment of short-term debt	0	(1,822,747)
Withholding remittance - share-based compensation	(2,476)	(1,742)
Other	(12,210)	(12,642)
Net cash used in financing activities	(116,765)	(597,544)
Change in cash and cash equivalents	350,107	(41,942)
Cash and cash equivalents at beginning of period	106,536	123,078
Cash and cash equivalents at end of period	456,643	104,939
SUPPLEMENTAL INFORMATION:
Interest paid, net of amounts capitalized	204,135	196,609
Income taxes paid, net	8,108	5,957
Southwest Gas Corporation
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	163,991	150,565
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	220,663	218,763
Deferred income taxes	47,061	43,348
Gains on sale of property and equipment	0	(136)
Changes in undistributed stock compensation	6,901	5,395
Equity AFUDC	(5,548)	0
Changes in current assets and liabilities:
Accounts receivable, net of allowance	137,635	66,275
Accrued utility revenue	45,200	43,500
Deferred purchased gas costs	732,599	(237,017)
Accounts payable	(103,708)	(346,579)
Accrued taxes	5,935	8,782
Other current assets and liabilities	(92,639)	291,863
Changes in deferred charges and other assets	(39,098)	(21,750)
Changes in other liabilities and deferred credits	(24,537)	(54,894)
Net cash provided by operating activities	1,094,455	168,115
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(643,720)	(581,190)
Proceeds from the sale of property	21,377	0
Changes in customer advances	(4,804)	(6,974)
Other	244	670
Net cash provided by (used in) investing activities	(626,903)	(587,494)
CASH FLOW FROM FINANCING ACTIVITIES:
Contribution from parent	0	530,000
Dividends paid	(133,500)	(111,200)
Issuance of long-term debt, net	0	297,759
Change in long-term credit facility and commercial paper	0	(50,000)
Issuance of short-term debt	0	450,000
Repayment of short-term debt	0	(675,000)
Withholding remittance - share-based compensation	(1,801)	(1,528)
Other	(1,752)	(1,505)
Net cash used in financing activities	(137,053)	438,526
Change in cash and cash equivalents	330,499	19,147
Cash and cash equivalents at beginning of period	71,154	51,823
Cash and cash equivalents at end of period	401,653	70,970
SUPPLEMENTAL INFORMATION:
Interest paid, net of amounts capitalized	111,610	99,425
Income taxes paid, net	$ 0	$ 0

CONDENSED CONSOLIDATED STATEM_8

CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - Southwest - USD ($) $ in Thousands	Total	Southwest Gas Corporation	Common stock shares	Common stock shares 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
Beginning balance (in shares) at Dec. 31, 2022			67,119,000	47,482,000
Beginning balance at Dec. 31, 2022			$ 68,749	$ 49,112	$ 2,287,183	$ 1,622,969	$ (44,242)	$ (38,261)	$ 747,069	$ 935,355
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)									78,020	150,565
Share-based compensation						4,305				(438)
Contributions from Southwest Gas Holdings, Inc.						530,000
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax							589	589
Dividends declared to Southwest Gas Holdings, Inc.									(133,879)	(118,900)
Ending balance (in shares) at Sep. 30, 2023			71,515,000
Ending balance at Sep. 30, 2023	$ 3,238,745	$ 3,135,296	$ 73,145		2,539,759	2,157,274	(43,523)	(37,672)	669,364	966,582
Beginning balance (in shares) at Jun. 30, 2023			71,473,000	47,482,000
Beginning balance at Jun. 30, 2023			$ 73,103	$ 49,112	2,534,223	2,156,026	(41,458)	(37,868)	696,958	1,009,608
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)									3,231	(3,251)
Share-based compensation						1,248				(75)
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax							196	196
Dividends declared to Southwest Gas Holdings, Inc.									(44,584)	(39,700)
Ending balance (in shares) at Sep. 30, 2023			71,515,000
Ending balance at Sep. 30, 2023	$ 3,238,745	3,135,296	$ 73,145		2,539,759	2,157,274	(43,523)	(37,672)	669,364	966,582
Beginning balance (in shares) at Dec. 31, 2023	71,563,750		71,564,000	47,482,000
Beginning balance at Dec. 31, 2023	$ 3,310,036		$ 73,194	$ 49,112	2,541,790	2,156,577	(43,787)	(40,548)	738,839	1,018,474
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)									106,359	163,991
Share-based compensation						5,619				(517)
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax							1,154	1,154
Dividends declared to Southwest Gas Holdings, Inc.									(134,064)	(138,300)
Ending balance (in shares) at Sep. 30, 2024	71,740,332		71,740,000
Ending balance at Sep. 30, 2024	$ 3,632,250	3,215,562	$ 73,370		2,714,958	2,162,196	(43,875)	(39,394)	710,940	1,043,648
Beginning balance (in shares) at Jun. 30, 2024			71,709,000	47,482,000
Beginning balance at Jun. 30, 2024			$ 73,339	$ 49,112	2,709,674	2,160,535	(45,615)	(39,778)	755,367	1,087,666
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)									289	572
Share-based compensation						1,661				(90)
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax							384	384
Dividends declared to Southwest Gas Holdings, Inc.									(44,716)	(44,500)
Ending balance (in shares) at Sep. 30, 2024	71,740,332		71,740,000
Ending balance at Sep. 30, 2024	$ 3,632,250	$ 3,215,562	$ 73,370		$ 2,714,958	$ 2,162,196	$ (43,875)	$ (39,394)	$ 710,940	$ 1,043,648

Background, Organization, and S

Background, Organization, and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2024
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. (together with its subsidiaries, the “Company”) is a holding company, owning all of the shares of common stock of Southwest Gas Corporation (“Southwest” or the “natural gas distribution” segment), until April 22, 2024, all of the shares of common stock of Centuri Group, Inc. (“utility infrastructure services” segment), and until February 14, 2023, all of the shares of common stock of MountainWest Pipelines Holding Company (“MountainWest” or the “pipeline and storage” segment). References throughout this document to “Centuri” relate to Centuri Group, Inc., for periods prior to April 22, 2024, or subsequently, to Centuri Holdings, Inc. In December 2022, the Company announced that its Board of Directors (the “Board”) unanimously determined to take strategic actions to simplify the Company’s portfolio of businesses. These actions included entering into a definitive agreement to sell 100% of MountainWest to Williams Partners Operating LLC for $1.5 billion in total enterprise value, subject to certain adjustments. The sale closed on February 14, 2023. Also as part of this simplification strategy, the Company previously communicated that it would pursue a separation of Centuri. In April 2024, the Company and Centuri Holdings, Inc. announced the completion of an initial public offering of Centuri Holdings, Inc. common stock (the “Centuri IPO”). Following the Centuri IPO, the Company owns approximately 81% of Centuri. Through the first quarter of 2024 and leading up to the Centuri IPO, Centuri continued to be wholly owned by Southwest Gas Holdings, Inc. Centuri continues to be consolidated as part of these financial statements, and will continue to be consolidated until such time as the conditions for consolidation are no longer met. Centuri now makes separate filings with the Securities and Exchange Commission (the “SEC”) as a public company. The Company’s common stock continues to trade under the ticker symbol “SWX,” while Centuri’s common stock trades under the ticker symbol “CTRI.” See Note 8 - Centuri Separation . On October 15, 2024, the Company and Carl C. Icahn and the persons and entities listed therein (collectively, the “Icahn Group”) entered into an Amended and Restated Cooperation Agreement (the “Amended Agreement”), which amends, restates, supersedes, and replaces in its entirety the Amended and Restated Cooperation Agreement entered into on November 21, 2023. In accordance with the terms of the Amended Agreement, the Company agreed with the Icahn Group, among other things, to nominate Andrew W. Evans, Henry P. Linginfelter, Ruby Sharma, and Andrew J. Teno (collectively, the “Icahn Designees”) for election at the Company’s 2025 Annual Meeting of Stockholders (the “2025 Annual Meeting”). In addition, the Amended Agreement provides that the standstill restrictions on the Icahn Group will remain in effect until, and the Amended Agreement will terminate upon, the later of (x) the conclusion of the 2025 Annual Meeting and (y) the earlier of (1) immediately following the time at which Mr. Teno (or any replacement designee for Mr. Teno) is no longer serving on the Company’s Board and (2) thirty days prior to the expiration of the advance notice deadline for submission of director nominees in connection with the Company’s 2026 Annual Meeting of Stockholders; provided, however, that the Amended Agreement will terminate automatically on the date on which the Board re-appoints as a director any former director of the Board, without the approval of a majority of the Icahn Designees. The Company further agreed with the Icahn Group to establish the record date for the 2025 Annual Meeting for a time within thirty days of March 4, 2025. Other than the foregoing, the material terms of the prior agreement remain unchanged. 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, highlighted by the continuation of a significant cash balance existing as of the end of the third quarter of 2024, reflective of the collection of gas costs under purchased gas cost mechanisms as a component of customer bills. While mechanisms exist in all states in which Southwest operates, which effectively and primarily decouple authorized operating cost recovery and profitability from the volume of natural gas sold, thereby also incentivizing energy conservation, results for the natural gas distribution segment are higher during winter periods due to the seasonality incorporated in its regulatory rate structures. Centuri is a strategic utility infrastructure services company dedicated to partnering with North America’s gas and electric providers to build and maintain the energy network that powers millions of homes across the United States (“U.S.”) and Canada. Centuri derives revenue primarily from installation, replacement, repair, and maintenance of energy networks. Centuri operates in the U.S., primarily as NPL, Neuco, Linetec, and Riggs Distler, and in Canada, primarily as NPL Canada. Utility infrastructure services activity is seasonal in many of Centuri’s operating areas. Peak periods are the summer and fall months in colder climate areas, such as the northeastern and midwestern U.S. and in Canada. In warmer climate areas, such as the southwestern and southeastern U.S., utility infrastructure services activity continues year round. Basis of Presentation. The condensed consolidated financial statements of Southwest Gas Holdings, Inc. and its subsidiaries, and of Southwest Gas Corporation (with its subsidiaries) included herein have been prepared pursuant to the rules and regulations of the SEC. The year-end 2023 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. 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, as of the date of the financial statements, as well as 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 statement of results for the interim periods, have been made. Centuri and the Company do not always have the same basis of presentation, which could result in differences between the amounts presented in the Company’s financial information related to Centuri, and amounts included in Centuri’s separate publicly filed financial information. During the three months ended September 30, 2024, Centuri entered into an agreement for the securitization of accounts receivable, which includes the consolidation of a newly formed special purpose entity, and the derecognition of accounts receivable that are sold, due to the lack of continuing involvement following their sale to a third party. Refer to Note 3 – Revenue for further details. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto of Southwest and the Company included in our 2023 Annual Report on Form 10-K for the fiscal year ended December 31, 2023. In the first quarter of 2023, management identified a misstatement related to its accounting for the cost of gas sold at Southwest, thereby determining that Net cost of gas sold was overstated in 2021 and 2022 by $2.3 million and $5.7 million, respectively. Southwest made an adjustment in the first quarter of 2023 to reduce Net cost of gas sold and to increase its asset balance for Deferred purchased gas costs by $8 million. Also in the first quarter of 2023, the Company identified an approximately $21 million misstatement related to its initial estimation of the loss recorded upon reclassifying MountainWest as an asset held for sale during the year ended December 31, 2022. Consequently, the impairment loss for the year ended December 31, 2022 was understated by approximately $21 million, which was corrected in the first quarter of 2023. The Company (and Southwest, with respect to Net cost of gas sold) assessed, both quantitatively and qualitatively, the impact of these items on previously issued financial statements, concluding they were not material to any earlier period or to the period of correction. Other Property and Investments. Other property and investments on Southwest’s and the Company’s Condensed Consolidated Balance Sheets includes: (Thousands of dollars) September 30, 2024 December 31, 2023 Net cash surrender value of COLI policies $ 154,673 $ 146,546 Other property 4,501 6,112 Total Southwest Gas Corporation 159,174 152,658 Non-regulated property, equipment, and intangibles 1,718,709 1,752,094 Non-regulated accumulated provision for depreciation and amortization (725,942) (675,632) Other property and investments 41,121 37,220 Total Southwest Gas Holdings, Inc. $ 1,193,062 $ 1,266,340 Held for sale. In the first quarter of 2023, the Company and Southwest concluded certain assets associated with their previous corporate headquarters met the criteria to be classified as held for sale. As a result, the Company and Southwest reclassified approximately $27 million from Other property and investments to Current assets held for sale on their respective Condensed Consolidated Balance Sheets in the first quarter of 2023. Also in 2023, the Company and Southwest recorded an estimated loss of $5.2 million on the assets based upon an updated fair value less costs to sell. The sale was completed in January 2024. Cash and Cash Equivalents. Cash and cash equivalents of the Company include $173.4 million and $48.9 million of money market fund investments at September 30, 2024 and December 31, 2023, respectively. Of these amounts, $141.7 million and $38.6 million at September 30, 2024 and December 31, 2023, respectively, were held by Southwest. Noncash investing activities include capital expenditures that were not yet paid, thereby remaining in accounts payable, amounts related to which declined by approximately $28.1 million and $17 million for the Company and Southwest, respectively, during the nine months ended September 30, 2024; and declined approximately $39.6 million and $35.2 million during the nine months ended September 30, 2023, for the Company and Southwest, respectively. The Company and Southwest expanded their presentation in the first quarter 2024 to show the Change in short-term portion of credit facility and Repayment of short-term debt as separate line items within their Condensed Consolidated Statements of Cash Flows. The comparable prior-year period has been updated to reflect this change. Prepaid and other current assets. Prepaid and other current assets for the Company and Southwest include, among other things, materials and operating supplies of $77.5 million at September 30, 2024 and $83.4 million at December 31, 2023 (carried at weighted average cost). Goodwill. Goodwill is assessed as of October 1 each year for impairment, or more frequently, if circumstances indicate an impairment to the carrying value of goodwill may have occurred. The Company’s reporting units for goodwill are its operating segments, which are also its reportable segments. Since December 31, 2023, management qualitatively assessed whether events during the first nine months of 2024 indicated it was more likely than not that the fair value of our reporting units was less than their carrying value, which if the case, could be an indication of a goodwill impairment. Through management’s assessments, no impairment was deemed to have occurred in the continuing segments of the Company. Goodwill in the Natural Gas Distribution and Utility Infrastructure Services segments is included in the respective Condensed Consolidated Balance Sheets as follows: (Thousands of dollars) Natural Gas Utility Infrastructure Total Company December 31, 2023 $ 11,155 $ 778,574 $ 789,729 Foreign currency translation adjustment — (2,134) (2,134) September 30, 2024 $ 11,155 $ 776,440 $ 787,595 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 the Company include $44.5 million and $44.4 million of dividends declared as of September 30, 2024 and December 31, 2023, respectively. Also included in the balance for the Company and Southwest was $33.5 million and $87.6 million in accrued purchased gas costs as of September 30, 2024 and December 31, 2023, respectively. Other Income (Deductions). The following table provides the composition of significant items included in Other income (deductions) in Southwest’s and the Company’s Condensed Consolidated Statements of Income: Three Months Ended September 30, Nine Months Ended (Thousands of dollars) 2024 2023 2024 2023 Southwest Gas Corporation: Change in COLI policies $ 3,200 $ (1,500) $ 7,800 $ 4,800 Interest income 8,736 13,249 27,649 40,235 Equity AFUDC 1,874 — 5,548 — Other components of net periodic benefit cost 4,131 5,097 12,392 15,290 Miscellaneous expense (1,276) (2,309) (4,413) (8,603) Southwest Gas Corporation - total other income (deductions) 16,665 14,537 48,976 51,722 Centuri, MountainWest, and Southwest Gas Holdings, Inc.: Foreign transaction gain (loss) (5) 18 (6) (399) Equity AFUDC — — — 82 Equity in earnings (loss) of unconsolidated investments 127 142 (30) 591 Miscellaneous income and (expense) 37 (50) 935 466 Corporate and administrative (66) (183) (57) 66 Southwest Gas Holdings, Inc. - total other income (deductions) $ 16,758 $ 14,464 $ 49,818 $ 52,528 Interest income primarily relates to Southwest’s regulatory asset balances, including its deferred purchased gas cost mechanisms, the combined balance of which ranged from an asset balance of $687 million as of September 30, 2023 to a net liability balance of $180 million as of September 30, 2024. I nterest income is earned on asset balances and interest expense is incurred on liability balances. Refer also to Note 2 – Components of Net Periodic Benefit Cost for details regarding Other components of net periodic benefit cost. Noncontrolling Interest . In connection with the Centuri IPO, the Company recorded a noncontrolling intere st as part of equity in the Condensed Consolidated Balance Sheet (associated with the interests held by the new investors in Centuri), and recognized the excess of the fair value of the Centuri IPO proceeds over the carrying value of the noncontrolling interest, in addition to a portion of Accumulated other comprehensive loss relevant to the proportional interest of the noncontrolling parties in Centuri, within Additional paid-in capital. The Condensed Consolidated Statements of Income include multiple components of comprehensive income attributable to noncontrolling interests following the Centuri IPO. These amounts, including those distinguishable from net income attributed to these parties, are separately presented in the Condensed Consolidated Statements of Equity. Refer also to Note 8 - Centuri Separation . Redeemable Noncontrolling Interests . Separate from the noncontrolling ownership interests in Centuri, in connection with the earlier acquisition of Linetec, by Centuri, in November 2018, the previous Linetec owner initially retained a 20% equity interest in that entity, with redemption of that interest being subject to certain rights based on the passage of time or upon the occurrence of certain triggering events. Effective in 2022, the Company, through Centuri, had the right, but not the obligation, to purchase at fair value (subject to a floor) a portion of the interest held by the previous Linetec owner, and in incremental amounts each year thereafter. In March 2022, the parties agreed to a partial redemption, reducing the noncontrolling interest to 15%, and in March 2023, agreed to a partial 5% redemption (of the 15% then remaining). In April 2023, Centuri paid $39.9 million to the previous Linetec owner, thereby reducing the balance continuing to be redeemable at that time to 10% under the terms of the original agreement. In March 2024, the parties entered into an agreement to redeem the remaining 10% equity interest for $92 million, which resulted in Centuri owning all of the equity interest in Linetec as of March 31, 2024. Centuri paid the total amount payable under the terms of the redemption agreement in April 2024. Separately, certain members of Riggs Distler management hold a 1.41% interest in Drum Parent, Inc. (“Drum”), the parent of Riggs Distler, which is redeemable, subject to certain rights based on the passage of time or upon the occurrence of certain triggering events. A portion of the redeemable noncontrolling interest was funded through promissory notes made to noncontrolling interest holders bearing interest at the prime rate plus 2%. During the first quarter of 2024, Centuri forgave all outstanding promissory notes and unpaid interest owed from the Riggs Distler noncontrolling interest holders and in exchange, obtained a 0.47% portion of the equity interest in Drum that had been funded through these notes. This comprises most of the change noted below as redemption of Drum interests during the first nine months of 2024. Additionally, during the first quarter of 2024, Centuri reached an agreement to purchase 0.13% of the noncontrolling interest in Drum for $0.8 million, the majority of which was accrued in March 2024 and ultimately paid in April 2024. The remaining noncontrolling interest in Drum outstanding as of September 30, 2024 was 0.81%, with Centuri owning over 99% of Drum following these events. Significant changes in the value of the redeemable noncontrolling interests, above a floor determined at the establishment 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. Valuation adjustments also impact retained earnings, as reflected in the Company’s Condensed Consolidated Statement of Equity, but do not impact net income. The following depicts changes to the balances of the redeemable noncontrolling interests: (Thousands of dollars) Linetec Drum Total Balance, December 31, 2023 $ 91,978 $ 12,689 $ 104,667 Net income (loss) attributable to redeemable noncontrolling interests (193) 63 (130) Redemption value adjustments 194 — 194 Redemption of redeemable noncontrolling interest (91,979) (5,046) (97,025) Balance, September 30, 2024 $ — $ 7,706 $ 7,706 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 share units 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 (In thousands) 2024 2023 2024 2023 Weighted average basic shares 71,880 71,626 71,816 70,488 Effect of dilutive securities: Restricted stock units (1) 206 225 178 188 Weighted average diluted shares 72,086 71,851 71,994 70,676 (1) The number of securities included 165,000 and 189,000 performance share units during the three months ended September 30, 2024 and September 30, 2023, the total of which was derived by assuming that target performance will be achieved during the relevant performance period. During the nine months ended September 30, 2024 and September 30, 2023, respectively, the number of securities included 148,000 and 160,000 performance share units, the total of which was derived by assuming that target performance will be achieved during the relevant performance period. Income Taxes. The Company’s effective tax rate was (421.1)% for the three months ended September 30, 2024, compared to (47.1)% for the corresponding period in 2023, primarily due to pre-tax income differences, the amortization of excess deferred income taxes, and corporate-owned life insurance (“COLI”). The Company’s effective tax was 14.8% for the nine months ended September 30, 2024, compared to 28.2% for the corresponding period in 2023, primarily due to amortization of excess deferred income taxes, nondeductible costs associated with the Centuri IPO, and the MountainWest sale in 2023, which included the impact of book versus tax basis differences related to that transaction. The tax impacts of further separation of Centuri will depend on the ultimate separation path (See Note 8 - Centuri Separation ). Southwest’s effective tax rate was 113.0% for the three months ended September 30, 2024, compared to 65.3% for the corresponding period in 2023 primarily due to pre-tax income differences, the amortization of excess deferred income taxes, and the impacts of COLI. Southwest’s effective tax rate was 14.2% for the nine months ended September 30, 2024, compared to 12.9% in the corresponding period in 2023 primarily due to the amortization of excess accumulated deferred income taxes and COLI. In April 2023, the Internal Revenue Service issued Revenue Procedure 2023-15, which provides a safe harbor method of accounting that taxpayers may use to determine whether expenditures to repair, maintain, replace, or improve natural gas transmission and distribution property must be capitalized for tax purposes. The Company intends to adopt this change in tax accounting method with its 2024 U.S. federal income tax return filing in 2025, and it expects the safe harbor method to increase tax repair deductions. The effects of the change in method are not expected to be material to the financial statements overall, as this change will result in an increase in a deferred tax liability offset by a net operating loss position deferred tax asset. Recent Accounting Standards Updates. Recently issued accounting pronouncement that will be effective in 2024 and later periods: In November 2023, the Financial Accounting Standards Board (the “FASB”) issued ASU 2023-07 “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures.” The update, among other amendments, requires disclosure of significant segment expenses that are regularly provided to the chief operating decision maker (“CODM”) and included within each reported measure of segment profit or loss, as well as an amount and description of the composition of other segment items to reconcile to segment profit or loss. The update also requires the title and position of the entity’s CODM to be disclosed, and extends certain annual disclosures to interim periods. The provisions of the update are effective for fiscal years beginning after December 15, 2023 and interim periods within the fiscal years beginning after December 15, 2024. Early adoption is permitted. The Company and Southwest expect that the adoption of this guidance will only impact disclosures, with no impact on results of operations, cash flows, or financial condition. Recently issued accounting pronouncement that will be effective after 2024:

Components of Net Periodic Bene

Components of Net Periodic Benefit Cost	9 Months Ended
Components of Net Periodic Benefit Cost	Sep. 30, 2024
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost	Note 2 – Components of Net Periodic Benefit Cost The components of Southwest's net periodic benefit cost for its pension plan, supplemental retirement plan ("SERP"), and postretirement benefits other than pensions ("PBOP") for the three and nine months ended September 30, 2024 and 2023 are presented in the following tables. Qualified Retirement Plan September 30, Three Months Nine Months 2024 2023 2024 2023 (Thousands of dollars) Service cost $ 7,063 $ 6,460 $ 21,189 $ 19,380 Interest cost 15,097 14,791 45,291 44,373 Expected return on plan assets (21,953) (21,015) (65,859) (63,045) Amortization of net actuarial loss 1,577 84 4,731 252 Net periodic benefit cost $ 1,784 $ 320 $ 5,352 $ 960 SERP September 30, Three Months Nine Months 2024 2023 2024 2023 (Thousands of dollars) Service cost $ 61 $ 62 $ 183 $ 186 Interest cost 542 531 1,626 1,593 Amortization of net actuarial loss 333 249 999 748 Net periodic benefit cost $ 936 $ 842 $ 2,808 $ 2,527 PBOP September 30, Three Months Nine Months 2024 2023 2024 2023 (Thousands of dollars) Service cost $ 322 $ 317 $ 966 $ 951 Interest cost 794 825 2,383 2,475 Expected return on plan assets (565) (606) (1,695) (1,818) Amortization of prior service costs 44 44 132 132 Net periodic benefit cost $ 595 $ 580 $ 1,786 $ 1,740

Revenue

Revenue	9 Months Ended
Revenue	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue	Note 3 – Revenue The following information about the Company’s revenues is presented by segment. Southwest encompasses the natural gas distribution segment and Centuri encompasses the utility infrastructure services segment. Natural Gas Distribution Segment : Southwest’s operating revenues included 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, in addition to other categories of revenue: Three Months Ended Nine Months Ended (Thousands of dollars) 2024 2023 2024 2023 Residential $ 189,156 $ 215,376 $ 1,283,945 $ 1,277,363 Small commercial 70,708 85,955 387,793 366,667 Large commercial 20,569 27,888 87,895 84,021 Industrial/other 13,443 16,596 49,737 52,165 Transportation 27,515 23,278 82,875 77,558 Revenue from contracts with customers 321,391 369,093 1,892,245 1,857,774 Alternative revenue program revenues (deferrals) 34,341 21,840 17,978 (72,251) Other revenues (1) 3,399 3,670 11,934 11,825 Total Regulated operations revenues $ 359,131 $ 394,603 $ 1,922,157 $ 1,797,348 (1) Amounts include late fees and other miscellaneous revenues, and may also include the impact of certain regulatory mechanisms. Utility Infrastructure Services Segment : During the fourth quarter of 2023, utility infrastructure services segment management, in connection with Centuri’s planned separation, changed its service type revenue classification to align with changes in its organizational structure, and as a result, prior year “other” revenue has been recast into gas infrastructure services or electric power infrastructure services to reflect these changes, with no impact to revenue overall. 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 Nine Months Ended (Thousands of dollars) 2024 2023* 2024 2023* Service Types: Gas infrastructure services $ 416,424 $ 450,335 $ 1,059,326 $ 1,188,941 Electric power infrastructure services 300,510 314,850 845,699 1,008,911 Other 3,119 9,704 15,126 36,109 Total Utility infrastructure services revenues $ 720,053 $ 774,889 $ 1,920,151 $ 2,233,961 *The three months ended September 30, 2023 were previously presented as: Gas infrastructure services of $443,083, Electric power infrastructure services of $200,547, and Other of $131,259. The nine months ended September 30, 2023 were previously presented as: Gas infrastructure services of $1,173,960, Electric power infrastructure services of $668,681, and Other of $391,320. Three Months Ended Nine Months Ended (Thousands of dollars) 2024 2023 2024 2023 Contract Types: Master services agreement $ 569,000 $ 631,913 $ 1,571,701 $ 1,830,242 Bid contract 151,053 142,976 348,450 403,719 Total Utility infrastructure services revenues $ 720,053 $ 774,889 $ 1,920,151 $ 2,233,961 Unit price contracts $ 412,871 $ 440,787 $ 1,119,161 $ 1,191,889 Fixed price contracts 138,242 165,637 383,090 521,722 Time and materials contracts 168,940 168,465 417,900 520,350 Total Utility infrastructure services revenues $ 720,053 $ 774,889 $ 1,920,151 $ 2,233,961 The following table provides information about contracts receivable and revenue earned on contracts in progress in excess of billings (contract assets), both of which are included within Accounts receivable, net of allowances, as well as amounts billed in excess of revenue earned on contracts (contract liabilities) at Centuri, which are included in Other current liabilities as of September 30, 2024 and December 31, 2023 on the Company’s Condensed Consolidated Balance Sheets: (Thousands of dollars) September 30, 2024 December 31, 2023 Contracts receivable, net $ 253,019 $ 347,454 Revenue earned on contracts in progress in excess of billings 288,568 269,808 Amounts billed in excess of revenue earned on contracts 21,894 43,694 Revenue earned on contracts in progress in excess of billings (contract assets) that are not expected to be invoiced and collected within a year from the financial statement date are not included in the table above, and were $24.1 million as of September 30, 2024, and $0.2 million as of December 31, 2023. These non-current balances were included in Deferred charges and other assets on the Company’s Condensed Consolidated Balance Sheets. These contract assets primarily relate to Centuri’s rights to consideration for work completed, but not billed and/or approved for billing at the reporting date, and are transferred to contracts receivable when the rights become unconditional. The amounts billed in excess of revenue earned primarily relate to the advance consideration received from customers for which work has not yet been completed. The decrease in the contract liability balance from December 31, 2023 to September 30, 2024 of $21.8 million was due to revenue recognized during the period, net of new payments received in advance of work performed. 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. Furthermore, 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, 2024, Centuri had 42 fixed price 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, 2024 was $249.1 million. Centuri expects to recognize the remaining performance obligations over approximately the next two years; however, the timing of that recognition is largely within the control of the customer, including when the necessary 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, 2024 December 31, 2023 Billed on completed contracts and contracts in progress $ 253,809 $ 348,021 Other receivables 2,115 1,945 Contracts receivable, gross 255,924 349,966 Allowance for doubtful accounts (2,905) (2,512) Contracts receivable, net $ 253,019 $ 347,454 In September 2024, Centuri Group, Inc. and certain other subsidiaries of Centuri Holdings, Inc. entered into a three-year Accounts Receivable Securitization Facility (“the Facility”) for an aggregate amount of up to $125 million with PNC Bank, National Association (“PNC”), to enhance Centuri’s financial flexibility by providing additional liquidity. Under the Facility, certain designated subsidiaries of Centuri have sold and/or contributed, and will continue to sell and/or contribute, their trade accounts receivable and contract assets generated in the ordinary course of business to an indirect wholly owned bankruptcy-remote Special Purpose Entity (“SPE”) of Centuri created specifically for this purpose. The SPE is a variable interest entity, and Centuri is the primary beneficiary and therefore consolidates the SPE. The SPE transfers ownership and control of accounts receivable (but not contract assets) to PNC for payments as set forth in the receivables purchase agreement. Centuri and its related subsidiaries have no continuing involvement in the transferred accounts receivable, other than collection and administrative responsibilities, and, once sold, the accounts receivable are no longer available to satisfy Centuri’s creditors or those of its related subsidiaries. Centuri has not recorded any servicing asset or liability related to this continuing involvement as Centuri has determined it is compensated adequately for its servicing role. Centuri accounts for accounts receivable sold to PNC as a sale of financial assets and has derecognized the accounts receivable from its consolidated balance sheet for the current period. In addition, Centuri has agreed to guarantee the performance of the indirect wholly-owned subsidiaries and Centuri Group, Inc. as the servicer, of their respective obligations under the documentation for the Facility. Centuri is not guaranteeing the collectibility of the receivables or the creditworthiness of the related obligors. The Facility is subject to yield charges based upon a rate as specified in the receivables purchase agreement. Centuri may incur a recourse obligation in limited circumstances, but has determined this liability is not material. The total outstanding balance of accounts receivable that have been sold and derecognized is $125 million as of September 30, 2024. Additionally, the SPE owned unsold accounts receivable and contract assets of $60.6 million and $115.5 million, respectively, as of September 30, 2024, which are pledged as collateral to PNC. These balances are primarily included in Accounts receivable, net of allowances in the Company’s Condensed Consolidated Balance Sheet, with certain non-current balances included in Deferred charges and other assets. For the nine months ended September 30, 2024, Centuri received $125 million in cash proceeds from the Facility, which are included in cash from operating activities in the Condensed Consolidated Statement of Cash Flows and had no repayments to the Facility. As of September 30, 2024, Centuri had no available capacity under the Facility.

Common Stock

Common Stock	9 Months Ended
Common Stock	Sep. 30, 2024
Equity [Abstract]
Common Stock	Note 4 – Common Stock Shares of the Company’s common stock are publicly traded on the New York Stock Exchange, under the ticker symbol “SWX.” Share-based compensation related to Southwest and Centuri is based on stock awards to be issued in shares of Southwest Gas Holdings, Inc. On August 6, 2024, the Company entered into an Equity Distribution Agreement with J.P. Morgan Securities LLC and Wells Fargo Securities, LLC for the offer and sale of up to $340,000,000 of common stock from time to time in an “at-the-market” offering program (the “ATM Program”). The offering amount was carried forward from the Company’s previous at-the-market equity offering program. The shares are issuable pursuant to the Company’s automatic shelf registration statement on Form S-3 (File No. 333-275774). No issuances have occurred under the ATM Program as of September 30, 2024. During the nine months ended September 30, 2024, the Company issued approximately 78,000 shares of common stock through the Omnibus Incentive Plan. Additionally, during the nine months ended September 30, 2024, the Company issued 98,000 shares of common stock through the Dividend Reinvestment and Direct Stock Purchase Plan, raising approximately $6.9 million.

Debt

Debt	9 Months Ended
Debt	Sep. 30, 2024
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. Details surrounding the fair value and individual carrying values of instruments are provided in the table that follows. September 30, 2024 December 31, 2023 Carrying Fair Carrying Fair (Thousands of dollars) Southwest Gas Corporation: Debentures: 8% Series, due 2026 $ 75,000 $ 78,648 $ 75,000 $ 79,502 Medium-term notes, 7.92% series, due 2027 25,000 26,707 25,000 26,883 Medium-term notes, 6.76% series, due 2027 7,500 7,823 7,500 7,800 Notes, 5.8%, due 2027 300,000 311,610 300,000 309,180 Notes, 3.7%, due 2028 300,000 291,240 300,000 285,300 Notes, 5.45%, due 2028 300,000 309,360 300,000 307,170 Notes, 2.2%, due 2030 450,000 398,970 450,000 382,635 Notes, 4.05%, due 2032 600,000 570,300 600,000 563,940 Notes, 6.1%, due 2041 125,000 134,025 125,000 126,238 Notes, 4.875%, due 2043 250,000 225,975 250,000 214,050 Notes, 3.8%, due 2046 300,000 238,230 300,000 225,240 Notes, 4.15%, due 2049 300,000 241,830 300,000 236,370 Notes, 3.18%, due 2051 300,000 200,670 300,000 197,760 Unamortized discount and debt issuance costs (27,273) (29,594) 3,305,227 3,302,906 Revolving credit facility and commercial paper — — — — Industrial development revenue bonds: Tax-exempt Series A, due 2028 50,000 50,000 50,000 50,000 2003 Series A, due 2038 50,000 50,000 50,000 50,000 2008 Series A, due 2038 50,000 50,000 50,000 50,000 2009 Series A, due 2039 50,000 50,000 50,000 50,000 Unamortized discount and debt issuance costs (1,598) (1,363) 198,402 198,637 Less: current maturities — — Southwest Gas Corporation total long-term debt, less current maturities 3,503,629 3,501,543 Southwest Gas Holdings, Inc.: Centuri secured term loan facility 731,375 727,718 994,238 996,723 Centuri secured revolving credit facility 116,378 116,456 77,121 77,205 Other debt obligations 73,655 71,584 96,599 92,209 Unamortized discount and debt issuance costs (12,627) (17,111) Less: current maturities (30,264) (42,552) Southwest Gas Holdings, Inc. total long-term debt, less current maturities $ 4,382,146 $ 4,609,838 Southwest has a $400 million credit facility that was otherwise scheduled to expire in April 2025. However, in August 2024, Southwest entered into a new agreement to replace its existing credit facility. The agreement extends the maturity date to August 2029 and makes other miscellaneous changes, while the operation, designations, and key business terms are comparable to the prior facility. In regard to the facility in place as of September 2024, Southwest has designated $150 million of associated capacity as long-term debt and the remaining $250 million for working capital purposes. At September 30, 2024, the applicable margin is 1.125% for loans bearing interest with reference to the Secured Overnight Financing Rate (“SOFR”) and 0.125% for loans bearing interest with reference to the alternative base rate. At September 30, 2024, no borrowings were outstanding on the long-term portion (including under the commercial paper program), nor under the short-term portion of the facility. Centuri has a $1.545 billion secured revolving credit and term loan multi-currency facility. Amounts can be borrowed in either Canadian or U.S. dollars. The revolving credit facility matures on August 27, 2026 and the term loan facility matures on August 27, 2028. On May 13, 2024, Centuri amended its revolving credit facility to transition from Canadian Dollar Offered Rate benchmarks to Canadian Overnight Repo Rate Average (“CORRA”). The applicable margin for the revolving credit facility ranges from 1.0% to 2.5% for SOFR and CORRA loans and from 0.0% to 1.5% for “base rate” loans, depending on Centuri’s total net leverage ratio. The applicable margin for the term loan facility is 1.50% for base rate loans and 2.50% for SOFR loans. The capacity of the line of credit portion of the facility is $400 million; related amounts borrowed and repaid are available to be re-borrowed. The term loan portion of the facility has a limit of $1.145 billion. Centuri’s assets securing the facility at September 30, 2024 totaled $2.4 billion. At September 30, 2024, $847.8 million in borrowings were outstanding under Centuri’s combined secured revolving credit and term loan facility. On March 22, 2024, Centuri amended the financial covenants of its revolving credit facility and was required to maintain certain net leverage ratios. However, the amendment also provided that, in the event that a “Qualified IPO” (as defined in the amendment) is consummated prior to March 31, 2025, the maximum net leverage ratio would be reduced based on the amount of net proceeds received from such Qualified IPO. Pursuant to these terms, the completion of the Centuri IPO (which constituted a “Qualified IPO” for purposes of the amendment) resulted in a change to the maximum net leverage ratio. Based on the amount of proceeds received, Centuri was required to maintain a net leverage ratio of less than a maximum of 5.25 to 1.00 from April 18, 2024 through June 30, 2024, 5.00 to 1.00 from July 1, 2024 through September 29, 2024, 4.25 to 1.00 from September 30, 2024 through December 29, 2024, and 4.00 to 1.00 on December 30, 2024 and thereafter. The terms of the Centuri credit facility otherwise remain unchanged. Following the Centuri IPO and private placement, Centuri used approximately $316 million of proceeds to pay down $156 million of debt under the existing line of credit and $160 million of debt under the term loan portion of the facility, with the remainder of the IPO proceeds used for general corporate purposes. Short-Term Debt Southwest Gas Holdings, Inc. has a $300 million credit facility that is scheduled to expire in December 2026 and is primarily used for short-term financing needs. There was $113 million outstanding under this credit facility as of September 30, 2024. In April 2023, Southwest Gas Holdings, Inc. entered into a $550 million Term Loan Credit Agreement (the “Term Loan”) that was set to mature in October 2024. Southwest Gas Holdings, Inc. utilized a majority of the proceeds to make an equity contribution to Southwest. In August 2024, the Company amended its Term Loan agreement, which extended the maturity date to July 31, 2025 and changed the interest with reference to SOFR from an applicable margin of 1.300% to 1.125%, among other miscellaneous changes.

Other Comprehensive Income and

Other Comprehensive Income and Accumulated Other Comprehensive Income	9 Months Ended
	Sep. 30, 2024
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 impacts 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 Three Months Ended (Thousands of dollars) Before- Tax Net-of- Before- Tax Net-of- Defined benefit pension plans: Amortization of prior service cost $ 44 $ (11) $ 33 $ 44 $ (11) $ 33 Amortization of net actuarial (gain)/loss 1,910 (458) 1,452 333 (80) 253 Regulatory adjustment (1,448) 347 (1,101) (118) 28 (90) Total other comprehensive income (loss) - Southwest Gas Corporation 506 (122) 384 259 (63) 196 Foreign currency translation adjustment 1,675 — 1,675 (2,261) — (2,261) Total other comprehensive income (loss) 2,181 (122) 2,059 (2,002) (63) (2,065) Total other comprehensive income (loss) - noncontrolling interest (2) (319) — (319) — — — Total other comprehensive income (loss) - Southwest Gas Holdings, Inc. $ 1,862 $ (122) $ 1,740 $ (2,002) $ (63) $ (2,065) Nine Months Ended Nine Months Ended (Thousands of dollars) Before- Tax Net-of- Before- Tax Net-of- Defined benefit pension plans: Amortization of prior service cost $ 132 $ (33) $ 99 $ 132 $ (33) $ 99 Amortization of net actuarial (gain)/loss 5,730 (1,375) 4,355 1,000 (240) 760 Regulatory adjustment (4,343) 1,043 (3,300) (356) 86 (270) Total other comprehensive income (loss) - Southwest Gas Corporation 1,519 (365) 1,154 776 (187) 589 Foreign currency translation adjustment (2,296) — (2,296) 130 — 130 Total other comprehensive income (loss) (777) (365) (1,142) 906 (187) 719 Total other comprehensive (income) loss - noncontrolling interest (2) (150) — (150) — — — Total other comprehensive income (loss) - Southwest Gas Holdings, Inc. $ (927) $ (365) $ (1,292) $ 906 $ (187) $ 719 (1) Tax amounts are calculated using a 24% rate. The Company has elected to indefinitely reinvest, in Canada, the earnings of Centuri’s Canadian subsidiaries, 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). (2) Amount reflects the portion of the foreign currency translation adjustment attributable to the noncontrolling interest in Centuri following the Centuri IPO. 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 Foreign Currency Items (Thousands of dollars) Before-Tax Tax After-Tax Before-Tax Tax After-Tax AOCI Beginning Balance AOCI December 31, 2023 $ (53,352) $ 12,804 $ (40,548) $ (3,239) $ — $ (3,239) $ (43,787) Foreign currency translation adjustment — — — (2,296) — (2,296) (2,296) Amortization of prior service cost (1) 132 (33) 99 — — — 99 Amortization of net actuarial loss (1) 5,730 (1,375) 4,355 — — — 4,355 Regulatory adjustment (2) (4,343) 1,043 (3,300) — — — (3,300) Net current period other comprehensive income (loss) 1,519 (365) 1,154 (2,296) — (2,296) (1,142) Less current period other comprehensive (income) loss attributable to noncontrolling interest (4) — — — (150) — (150) (150) Centuri IPO (5) — — — 1,204 — 1,204 1,204 Net current period other comprehensive income (loss) attributable to Southwest Gas Holdings, Inc. 1,519 (365) 1,154 (1,242) — (1,242) (88) Ending Balance AOCI September 30, 2024 $ (51,833) $ 12,439 $ (39,394) $ (4,481) $ — $ (4,481) $ (43,875) (1) 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). (2) 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 and Southwest’s Condensed Consolidated Balance Sheets). (3) Tax amounts are calculated using a 24% rate. (4) Amount reflects the foreign currency translation adjustment attributable to the noncontrolling interest in Centuri following the Centuri IPO. (5) Amount reflects the attributed proportion of the AOCI balance associated with the ownership interests in Centuri held by the new investors as of the Centuri IPO date, amounts for which were reclassified from AOCI to Additional paid-in capital on the Company’s Condensed Consolidated Balance Sheet. The following table represents a rollforward of AOCI, presented on Southwest’s Condensed Consolidated Balance Sheets: Defined Benefit Plans (Thousands of dollars) Before-Tax Tax (Expense) Benefit (8) After-Tax Beginning Balance AOCI December 31, 2023 $ (53,352) $ 12,804 $ (40,548) Amortization of prior service cost (6) 132 (33) 99 Amortization of net actuarial loss (6) 5,730 (1,375) 4,355 Regulatory adjustment (7) (4,343) 1,043 (3,300) Net current period other comprehensive income attributable to Southwest Gas Corporation 1,519 (365) 1,154 Ending Balance AOCI September 30, 2024 $ (51,833) $ 12,439 $ (39,394) (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, 2024 December 31, 2023 Net actuarial loss $ (356,238) $ (361,968) Prior service cost (1,046) (1,178) Less: amount recognized in regulatory assets 305,451 309,794 Recognized in AOCI $ (51,833) $ (53,352)

Segment Information

Segment Information	9 Months Ended
Segment Information	Sep. 30, 2024
Segment Reporting [Abstract]
Segment Information	Note 7 – Segment Information The Company has two reportable segments. Southwest comprises the natural gas distribution segment and Centuri comprises the utility infrastructure services segment. As a result of the MountainWest sale in February 2023 (previously comprising the pipeline and storage segment), the information for the nine months ended September 30, 2023 presented below for MountainWest reflects activity from January 1, 2023 through February 13, 2023 (the last full day of its ownership by the Company). Centuri accounts for services provided to Southwest at contractual prices. Accounts receivable for these services, which are not eliminated during consolidation, are presented in the table below: (Thousands of dollars) September 30, 2024 December 31, 2023 Centuri accounts receivable for services provided to Southwest $ 7,330 $ 13,017 In order to reconcile the table below to net income (loss) 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 distribution, utility infrastructure services, and pipeline and storage segments are as follows: (Thousands of dollars) Natural Gas Utility Infrastructure Pipeline and Storage Other Total Three Months Ended September 30, 2024 Revenues from external customers $ 359,131 $ 692,822 $ — $ — $ 1,051,953 Intersegment revenues — 27,231 — — 27,231 Total $ 359,131 $ 720,053 $ — $ — $ 1,079,184 Segment net income (loss) $ 572 $ 9,956 $ — $ (10,239) $ 289 Three Months Ended September 30, 2023 Revenues from external customers $ 394,603 $ 745,639 $ — $ — $ 1,140,242 Intersegment revenues — 29,250 — — 29,250 Total $ 394,603 $ 774,889 $ — $ — $ 1,169,492 Segment net income (loss) $ (3,251) $ 17,956 $ — $ (11,474) $ 3,231 (Thousands of dollars) Natural Gas Utility Infrastructure Pipeline and Storage Other Total Nine Months Ended September 30, 2024 Revenues from external customers $ 1,922,157 $ 1,840,961 $ — $ — $ 3,763,118 Intersegment revenues — 79,190 — — 79,190 Total $ 1,922,157 $ 1,920,151 $ — $ — $ 3,842,308 Segment net income (loss) $ 163,991 $ (21,220) $ — $ (36,412) $ 106,359 Nine Months Ended September 30, 2023 Revenues from external customers $ 1,797,348 $ 2,145,601 $ 35,132 $ — $ 3,978,081 Intersegment revenues — 88,360 — — 88,360 Total $ 1,797,348 $ 2,233,961 $ 35,132 $ — $ 4,066,441 Segment net income (loss) $ 150,565 $ 24,902 $ (16,288) $ (81,159) $ 78,020 The corporate and administrative activities for Southwest Gas Holdings, Inc. in the three months ending September 30, 2024 include approximately $11.5 million of interest expense, including amounts incurred under the $550 million Term Loan entered into in April 2023, along with the types of costs customarily incurred at the corporate/holding company level, offset by tax benefits experienced during the quarter.

Centuri Separation

Centuri Separation	9 Months Ended
Centuri Separation	Sep. 30, 2024
Discontinued Operations and Disposal Groups [Abstract]
Centuri Separation	Note 8 - Centuri Separation In April 2024, the Company and Centuri Holdings, Inc. announced the completion of the Centuri IPO of 12,400,000 shares of Centuri’s common stock at a price of $21.00 per share. Centuri granted the underwriters a 30-day option to purchase up to an additional 1,860,000 shares of its common stock, which was exercised. In addition, Centuri announced the concurrent private placement of an additional 2,591,929 shares at a price equal to the Centuri IPO price, with Icahn Partners LP and Icahn Partners Master Fund LP, investment entities associated with Carl C. Icahn. Centuri’s common stock is listed on the New York Stock Exchange under the symbol “CTRI” and began trading on April 18, 2024. The net proceeds to Centuri from the Centuri IPO and the concurrent private placement, after deducting underwriting discounts and commissions of $18 million and offering expenses, were approximately $328 million. Centuri used the proceeds to repay a portion (approximately $316 million) of outstanding indebtedness under its revolving credit and term loan facility, with the remainder for general corporate purposes. After completion of the Centuri IPO, the Company owns approximately 81% of all ownership interests in Centuri, and continues to consolidate the financial results of Centuri. As of the IPO date, management determined the carrying value of the noncontrolling interest based on the relationship that the ownership interest of the new investors bears to the carrying value (net assets) of Centuri (as reflected in the Company’s consolidated financial information). The difference between the fair value of proceeds from the Centuri IPO and the carrying value of the noncontrolling interest is reflected as an increase in Additional paid-in capital of the Company. As of September 30, 2024, $176.9 million is reflected as equity attributable to noncontrolling interest in the Company’s Condensed Consolidated Balance Sheet. Net income attributable to noncontrolling interests for the three- and nine- months ended September 30, 2024 were $2.3 million and $4.2 million, respectively, which reflect from the time of the closing of the Centuri IPO on April 22, 2024 through the period ended September 30, 2024. Refer to the Company’s Condensed Consolidated Statement of Income and the Condensed Consolidated Statement of Equity for impacts associated with the noncontrolling interest in Centuri. The following reflects the effects of changes in the Company’s ownership interest in Centuri on the Company’s equity: Nine Months Ended (Thousands of dollars) 2024 Net income attributable to Southwest Gas Holdings, Inc. $ 106,359 Increase in additional paid-in capital as a result of Centuri IPO 154,287 Change from net income attributable to Southwest Gas Holdings, Inc. and transfers from noncontrolling interest $ 260,646 The Company intends to further reduce its ownership in future periods by means of: sales of its remaining Centuri shares into the market, a distribution of Centuri shares to Company stockholders, an exchange of Centuri shares for Southwest Gas Holdings, Inc. shares, or a combination thereof. The Company entered into several agreements with Centuri Holdings, Inc. in connection with the Centuri IPO and the planned separation of Centuri, providing a framework for the relationship between the Company and Centuri after the Centuri IPO, including a Separation Agreement, a Tax Matters Agreement, and a Registration Rights Agreement. Centuri’s new Board of Directors includes certain overlapping board members with the Company, including Andrew W. Evans, Anne L. Mariucci, and Karen S. Haller (the Company’s Chief Executive Officer).

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net income attributable to Southwest Gas Holdings, Inc.	$ 289	$ 3,231	$ 106,359	$ 78,020

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Background, Organization, and_2

Background, Organization, and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	Nature of Operations. Southwest Gas Holdings, Inc. (together with its subsidiaries, the “Company”) is a holding company, owning all of the shares of common stock of Southwest Gas Corporation (“Southwest” or the “natural gas distribution” segment), until April 22, 2024, all of the shares of common stock of Centuri Group, Inc. (“utility infrastructure services” segment), and until February 14, 2023, all of the shares of common stock of MountainWest Pipelines Holding Company (“MountainWest” or the “pipeline and storage” segment). References throughout this document to “Centuri” relate to Centuri Group, Inc., for periods prior to April 22, 2024, or subsequently, to Centuri Holdings, Inc. 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, highlighted by the continuation of a significant cash balance existing as of the end of the third quarter of 2024, reflective of the collection of gas costs under purchased gas cost mechanisms as a component of customer bills. While mechanisms exist in all states in which Southwest operates, which effectively and primarily decouple authorized operating cost recovery and profitability from the volume of natural gas sold, thereby also incentivizing energy conservation, results for the natural gas distribution segment are higher during winter periods due to the seasonality incorporated in its regulatory rate structures.
Basis of Presentation	Basis of Presentation. The condensed consolidated financial statements of Southwest Gas Holdings, Inc. and its subsidiaries, and of Southwest Gas Corporation (with its subsidiaries) included herein have been prepared pursuant to the rules and regulations of the SEC. The year-end 2023 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. 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, as of the date of the financial statements, as well as 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 statement of results for the interim periods, have been made. Centuri and the Company do not always have the same basis of presentation, which could result in differences between the amounts presented in the Company’s financial information related to Centuri, and amounts included in Centuri’s separate publicly filed financial information. During the three months ended September 30, 2024, Centuri entered into an agreement for the securitization of accounts receivable, which includes the consolidation of a newly formed special purpose entity, and the derecognition of accounts receivable that are sold, due to the lack of continuing involvement following their sale to a third party. Refer to Note 3 – Revenue for further details. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto of Southwest and the Company included in our 2023 Annual Report on Form 10-K for the fiscal year ended December 31, 2023.
Held for sale	Held for sale.
Cash and Cash Equivalents	Cash and Cash Equivalents. Cash and cash equivalents of the Company include $173.4 million and $48.9 million of money market fund investments at September 30, 2024 and December 31, 2023, respectively. Of these amounts, $141.7 million and $38.6 million at September 30, 2024 and December 31, 2023, respectively, were held by Southwest. Noncash investing activities include capital expenditures that were not yet paid, thereby remaining in accounts payable, amounts related to which declined by approximately $28.1 million and $17 million for the Company and Southwest, respectively, during the nine months ended September 30, 2024; and declined approximately $39.6 million and $35.2 million during the nine months ended September 30, 2023, for the Company and Southwest, respectively.
Prepaid and other current assets	Prepaid and other current assets. Prepaid and other current assets for the Company and Southwest include, among other things, materials and operating supplies of $77.5 million at September 30, 2024 and $83.4 million at December 31, 2023 (carried at weighted average cost).
Goodwill	Goodwill.
Other Current Liabilities	Other Current Liabilities
Redeemable Noncontrolling Interests	Significant changes in the value of the redeemable noncontrolling interests, above a floor determined at the establishment 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. Valuation adjustments also impact retained earnings, as reflected in the Company’s Condensed Consolidated Statement of Equity, but do not impact net income.
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 share units and restricted stock units). Unless
Income Taxes	Income Taxes. The Company’s effective tax rate was (421.1)% for the three months ended September 30, 2024, compared to (47.1)% for the corresponding period in 2023, primarily due to pre-tax income differences, the amortization of excess deferred income taxes, and corporate-owned life insurance (“COLI”). The Company’s effective tax was 14.8% for the nine months ended September 30, 2024, compared to 28.2% for the corresponding period in 2023, primarily due to amortization of excess deferred income taxes, nondeductible costs associated with the Centuri IPO, and the MountainWest sale in 2023, which included the impact of book versus tax basis differences related to that transaction. The tax impacts of further separation of Centuri will depend on the ultimate separation path (See Note 8 - Centuri Separation ). Southwest’s effective tax rate was 113.0% for the three months ended September 30, 2024, compared to 65.3% for the corresponding period in 2023 primarily due to pre-tax income differences, the amortization of excess deferred income taxes, and the impacts of COLI. Southwest’s effective tax rate was 14.2% for the nine months ended September 30, 2024, compared to 12.9% in the corresponding period in 2023 primarily due to the amortization of excess accumulated deferred income taxes and COLI. In April 2023, the Internal Revenue Service issued Revenue Procedure 2023-15, which provides a safe harbor method of accounting that taxpayers may use to determine whether expenditures to repair, maintain, replace, or improve natural gas transmission and distribution property must be capitalized for tax purposes. The Company intends to adopt this change in tax accounting method with its 2024 U.S. federal income tax return filing in 2025, and it expects the safe harbor method to increase tax repair deductions. The effects of the change in method are not expected to be material to the financial statements overall, as this change will result in an increase in a deferred tax liability offset by a net operating loss position deferred tax asset.
Recent Accounting Standards Updates	Recent Accounting Standards Updates. Recently issued accounting pronouncement that will be effective in 2024 and later periods: In November 2023, the Financial Accounting Standards Board (the “FASB”) issued ASU 2023-07 “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures.” The update, among other amendments, requires disclosure of significant segment expenses that are regularly provided to the chief operating decision maker (“CODM”) and included within each reported measure of segment profit or loss, as well as an amount and description of the composition of other segment items to reconcile to segment profit or loss. The update also requires the title and position of the entity’s CODM to be disclosed, and extends certain annual disclosures to interim periods. The provisions of the update are effective for fiscal years beginning after December 15, 2023 and interim periods within the fiscal years beginning after December 15, 2024. Early adoption is permitted. The Company and Southwest expect that the adoption of this guidance will only impact disclosures, with no impact on results of operations, cash flows, or financial condition. Recently issued accounting pronouncement that will be effective after 2024:

Background, Organization, and_3

Background, Organization, and Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Other Property and Investments	Other property and investments on Southwest’s and the Company’s Condensed Consolidated Balance Sheets includes: (Thousands of dollars) September 30, 2024 December 31, 2023 Net cash surrender value of COLI policies $ 154,673 $ 146,546 Other property 4,501 6,112 Total Southwest Gas Corporation 159,174 152,658 Non-regulated property, equipment, and intangibles 1,718,709 1,752,094 Non-regulated accumulated provision for depreciation and amortization (725,942) (675,632) Other property and investments 41,121 37,220 Total Southwest Gas Holdings, Inc. $ 1,193,062 $ 1,266,340
Schedule of Goodwill	Goodwill in the Natural Gas Distribution and Utility Infrastructure Services segments is included in the respective Condensed Consolidated Balance Sheets as follows: (Thousands of dollars) Natural Gas Utility Infrastructure Total Company December 31, 2023 $ 11,155 $ 778,574 $ 789,729 Foreign currency translation adjustment — (2,134) (2,134) September 30, 2024 $ 11,155 $ 776,440 $ 787,595
Schedule of Significant Items Included in Other Income (Deductions)	The following table provides the composition of significant items included in Other income (deductions) in Southwest’s and the Company’s Condensed Consolidated Statements of Income: Three Months Ended September 30, Nine Months Ended (Thousands of dollars) 2024 2023 2024 2023 Southwest Gas Corporation: Change in COLI policies $ 3,200 $ (1,500) $ 7,800 $ 4,800 Interest income 8,736 13,249 27,649 40,235 Equity AFUDC 1,874 — 5,548 — Other components of net periodic benefit cost 4,131 5,097 12,392 15,290 Miscellaneous expense (1,276) (2,309) (4,413) (8,603) Southwest Gas Corporation - total other income (deductions) 16,665 14,537 48,976 51,722 Centuri, MountainWest, and Southwest Gas Holdings, Inc.: Foreign transaction gain (loss) (5) 18 (6) (399) Equity AFUDC — — — 82 Equity in earnings (loss) of unconsolidated investments 127 142 (30) 591 Miscellaneous income and (expense) 37 (50) 935 466 Corporate and administrative (66) (183) (57) 66 Southwest Gas Holdings, Inc. - total other income (deductions) $ 16,758 $ 14,464 $ 49,818 $ 52,528
Schedule of Redeemable Noncontrolling Interest	The following depicts changes to the balances of the redeemable noncontrolling interests: (Thousands of dollars) Linetec Drum Total Balance, December 31, 2023 $ 91,978 $ 12,689 $ 104,667 Net income (loss) attributable to redeemable noncontrolling interests (193) 63 (130) Redemption value adjustments 194 — 194 Redemption of redeemable noncontrolling interest (91,979) (5,046) (97,025) Balance, September 30, 2024 $ — $ 7,706 $ 7,706
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 (In thousands) 2024 2023 2024 2023 Weighted average basic shares 71,880 71,626 71,816 70,488 Effect of dilutive securities: Restricted stock units (1) 206 225 178 188 Weighted average diluted shares 72,086 71,851 71,994 70,676

Components of Net Periodic Be_2

Components of Net Periodic Benefit Cost (Tables)	9 Months Ended
Components of Net Periodic Benefit Cost (Tables)	Sep. 30, 2024
Retirement Benefits [Abstract]
Schedule of Net Periodic Benefit Costs	Qualified Retirement Plan September 30, Three Months Nine Months 2024 2023 2024 2023 (Thousands of dollars) Service cost $ 7,063 $ 6,460 $ 21,189 $ 19,380 Interest cost 15,097 14,791 45,291 44,373 Expected return on plan assets (21,953) (21,015) (65,859) (63,045) Amortization of net actuarial loss 1,577 84 4,731 252 Net periodic benefit cost $ 1,784 $ 320 $ 5,352 $ 960 SERP September 30, Three Months Nine Months 2024 2023 2024 2023 (Thousands of dollars) Service cost $ 61 $ 62 $ 183 $ 186 Interest cost 542 531 1,626 1,593 Amortization of net actuarial loss 333 249 999 748 Net periodic benefit cost $ 936 $ 842 $ 2,808 $ 2,527 PBOP September 30, Three Months Nine Months 2024 2023 2024 2023 (Thousands of dollars) Service cost $ 322 $ 317 $ 966 $ 951 Interest cost 794 825 2,383 2,475 Expected return on plan assets (565) (606) (1,695) (1,818) Amortization of prior service costs 44 44 132 132 Net periodic benefit cost $ 595 $ 580 $ 1,786 $ 1,740

Revenue (Tables)

Revenue (Tables)	9 Months Ended
Revenue (Tables)	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Schedule of Revenue Disaggregated by Service Type and Contract Type	Southwest’s operating revenues included 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, in addition to other categories of revenue: Three Months Ended Nine Months Ended (Thousands of dollars) 2024 2023 2024 2023 Residential $ 189,156 $ 215,376 $ 1,283,945 $ 1,277,363 Small commercial 70,708 85,955 387,793 366,667 Large commercial 20,569 27,888 87,895 84,021 Industrial/other 13,443 16,596 49,737 52,165 Transportation 27,515 23,278 82,875 77,558 Revenue from contracts with customers 321,391 369,093 1,892,245 1,857,774 Alternative revenue program revenues (deferrals) 34,341 21,840 17,978 (72,251) Other revenues (1) 3,399 3,670 11,934 11,825 Total Regulated operations revenues $ 359,131 $ 394,603 $ 1,922,157 $ 1,797,348 (1) Amounts include late fees and other miscellaneous revenues, and may also include the impact of certain regulatory mechanisms. Three Months Ended Nine Months Ended (Thousands of dollars) 2024 2023* 2024 2023* Service Types: Gas infrastructure services $ 416,424 $ 450,335 $ 1,059,326 $ 1,188,941 Electric power infrastructure services 300,510 314,850 845,699 1,008,911 Other 3,119 9,704 15,126 36,109 Total Utility infrastructure services revenues $ 720,053 $ 774,889 $ 1,920,151 $ 2,233,961 *The three months ended September 30, 2023 were previously presented as: Gas infrastructure services of $443,083, Electric power infrastructure services of $200,547, and Other of $131,259. The nine months ended September 30, 2023 were previously presented as: Gas infrastructure services of $1,173,960, Electric power infrastructure services of $668,681, and Other of $391,320. Three Months Ended Nine Months Ended (Thousands of dollars) 2024 2023 2024 2023 Contract Types: Master services agreement $ 569,000 $ 631,913 $ 1,571,701 $ 1,830,242 Bid contract 151,053 142,976 348,450 403,719 Total Utility infrastructure services revenues $ 720,053 $ 774,889 $ 1,920,151 $ 2,233,961 Unit price contracts $ 412,871 $ 440,787 $ 1,119,161 $ 1,191,889 Fixed price contracts 138,242 165,637 383,090 521,722 Time and materials contracts 168,940 168,465 417,900 520,350 Total Utility infrastructure services revenues $ 720,053 $ 774,889 $ 1,920,151 $ 2,233,961
Schedule 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	The following table provides information about contracts receivable and revenue earned on contracts in progress in excess of billings (contract assets), both of which are included within Accounts receivable, net of allowances, as well as amounts billed in excess of revenue earned on contracts (contract liabilities) at Centuri, which are included in Other current liabilities as of September 30, 2024 and December 31, 2023 on the Company’s Condensed Consolidated Balance Sheets: (Thousands of dollars) September 30, 2024 December 31, 2023 Contracts receivable, net $ 253,019 $ 347,454 Revenue earned on contracts in progress in excess of billings 288,568 269,808 Amounts billed in excess of revenue earned on contracts 21,894 43,694
Schedule of Utility Infrastructure Services Contracts Receivable	Utility infrastructure services contracts receivable consists of the following: (Thousands of dollars) September 30, 2024 December 31, 2023 Billed on completed contracts and contracts in progress $ 253,809 $ 348,021 Other receivables 2,115 1,945 Contracts receivable, gross 255,924 349,966 Allowance for doubtful accounts (2,905) (2,512) Contracts receivable, net $ 253,019 $ 347,454

Debt (Tables)

Debt (Tables)	9 Months Ended
Debt (Tables)	Sep. 30, 2024
Debt Disclosure [Abstract]
Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt	Details surrounding the fair value and individual carrying values of instruments are provided in the table that follows. September 30, 2024 December 31, 2023 Carrying Fair Carrying Fair (Thousands of dollars) Southwest Gas Corporation: Debentures: 8% Series, due 2026 $ 75,000 $ 78,648 $ 75,000 $ 79,502 Medium-term notes, 7.92% series, due 2027 25,000 26,707 25,000 26,883 Medium-term notes, 6.76% series, due 2027 7,500 7,823 7,500 7,800 Notes, 5.8%, due 2027 300,000 311,610 300,000 309,180 Notes, 3.7%, due 2028 300,000 291,240 300,000 285,300 Notes, 5.45%, due 2028 300,000 309,360 300,000 307,170 Notes, 2.2%, due 2030 450,000 398,970 450,000 382,635 Notes, 4.05%, due 2032 600,000 570,300 600,000 563,940 Notes, 6.1%, due 2041 125,000 134,025 125,000 126,238 Notes, 4.875%, due 2043 250,000 225,975 250,000 214,050 Notes, 3.8%, due 2046 300,000 238,230 300,000 225,240 Notes, 4.15%, due 2049 300,000 241,830 300,000 236,370 Notes, 3.18%, due 2051 300,000 200,670 300,000 197,760 Unamortized discount and debt issuance costs (27,273) (29,594) 3,305,227 3,302,906 Revolving credit facility and commercial paper — — — — Industrial development revenue bonds: Tax-exempt Series A, due 2028 50,000 50,000 50,000 50,000 2003 Series A, due 2038 50,000 50,000 50,000 50,000 2008 Series A, due 2038 50,000 50,000 50,000 50,000 2009 Series A, due 2039 50,000 50,000 50,000 50,000 Unamortized discount and debt issuance costs (1,598) (1,363) 198,402 198,637 Less: current maturities — — Southwest Gas Corporation total long-term debt, less current maturities 3,503,629 3,501,543 Southwest Gas Holdings, Inc.: Centuri secured term loan facility 731,375 727,718 994,238 996,723 Centuri secured revolving credit facility 116,378 116,456 77,121 77,205 Other debt obligations 73,655 71,584 96,599 92,209 Unamortized discount and debt issuance costs (12,627) (17,111) Less: current maturities (30,264) (42,552) Southwest Gas Holdings, Inc. total long-term debt, less current maturities $ 4,382,146 $ 4,609,838

Other Comprehensive Income an_2

Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Schedule of Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss)	Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss): Three Months Ended Three Months Ended (Thousands of dollars) Before- Tax Net-of- Before- Tax Net-of- Defined benefit pension plans: Amortization of prior service cost $ 44 $ (11) $ 33 $ 44 $ (11) $ 33 Amortization of net actuarial (gain)/loss 1,910 (458) 1,452 333 (80) 253 Regulatory adjustment (1,448) 347 (1,101) (118) 28 (90) Total other comprehensive income (loss) - Southwest Gas Corporation 506 (122) 384 259 (63) 196 Foreign currency translation adjustment 1,675 — 1,675 (2,261) — (2,261) Total other comprehensive income (loss) 2,181 (122) 2,059 (2,002) (63) (2,065) Total other comprehensive income (loss) - noncontrolling interest (2) (319) — (319) — — — Total other comprehensive income (loss) - Southwest Gas Holdings, Inc. $ 1,862 $ (122) $ 1,740 $ (2,002) $ (63) $ (2,065) Nine Months Ended Nine Months Ended (Thousands of dollars) Before- Tax Net-of- Before- Tax Net-of- Defined benefit pension plans: Amortization of prior service cost $ 132 $ (33) $ 99 $ 132 $ (33) $ 99 Amortization of net actuarial (gain)/loss 5,730 (1,375) 4,355 1,000 (240) 760 Regulatory adjustment (4,343) 1,043 (3,300) (356) 86 (270) Total other comprehensive income (loss) - Southwest Gas Corporation 1,519 (365) 1,154 776 (187) 589 Foreign currency translation adjustment (2,296) — (2,296) 130 — 130 Total other comprehensive income (loss) (777) (365) (1,142) 906 (187) 719 Total other comprehensive (income) loss - noncontrolling interest (2) (150) — (150) — — — Total other comprehensive income (loss) - Southwest Gas Holdings, Inc. $ (927) $ (365) $ (1,292) $ 906 $ (187) $ 719 (1) Tax amounts are calculated using a 24% rate. The Company has elected to indefinitely reinvest, in Canada, the earnings of Centuri’s Canadian subsidiaries, 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). (2) Amount reflects the portion of the foreign currency translation adjustment attributable to the noncontrolling interest in Centuri following the Centuri IPO.
Schedule of 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 Foreign Currency Items (Thousands of dollars) Before-Tax Tax After-Tax Before-Tax Tax After-Tax AOCI Beginning Balance AOCI December 31, 2023 $ (53,352) $ 12,804 $ (40,548) $ (3,239) $ — $ (3,239) $ (43,787) Foreign currency translation adjustment — — — (2,296) — (2,296) (2,296) Amortization of prior service cost (1) 132 (33) 99 — — — 99 Amortization of net actuarial loss (1) 5,730 (1,375) 4,355 — — — 4,355 Regulatory adjustment (2) (4,343) 1,043 (3,300) — — — (3,300) Net current period other comprehensive income (loss) 1,519 (365) 1,154 (2,296) — (2,296) (1,142) Less current period other comprehensive (income) loss attributable to noncontrolling interest (4) — — — (150) — (150) (150) Centuri IPO (5) — — — 1,204 — 1,204 1,204 Net current period other comprehensive income (loss) attributable to Southwest Gas Holdings, Inc. 1,519 (365) 1,154 (1,242) — (1,242) (88) Ending Balance AOCI September 30, 2024 $ (51,833) $ 12,439 $ (39,394) $ (4,481) $ — $ (4,481) $ (43,875) (1) 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). (2) 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 and Southwest’s Condensed Consolidated Balance Sheets). (3) Tax amounts are calculated using a 24% rate. (4) Amount reflects the foreign currency translation adjustment attributable to the noncontrolling interest in Centuri following the Centuri IPO. (5) Amount reflects the attributed proportion of the AOCI balance associated with the ownership interests in Centuri held by the new investors as of the Centuri IPO date, amounts for which were reclassified from AOCI to Additional paid-in capital on the Company’s Condensed Consolidated Balance Sheet. The following table represents a rollforward of AOCI, presented on Southwest’s Condensed Consolidated Balance Sheets: Defined Benefit Plans (Thousands of dollars) Before-Tax Tax (Expense) Benefit (8) After-Tax Beginning Balance AOCI December 31, 2023 $ (53,352) $ 12,804 $ (40,548) Amortization of prior service cost (6) 132 (33) 99 Amortization of net actuarial loss (6) 5,730 (1,375) 4,355 Regulatory adjustment (7) (4,343) 1,043 (3,300) Net current period other comprehensive income attributable to Southwest Gas Corporation 1,519 (365) 1,154 Ending Balance AOCI September 30, 2024 $ (51,833) $ 12,439 $ (39,394) (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.
Schedule of Amount Recognized Before Income Tax in Accumulated Other Comprehensive Income	The following table represents amounts (before income tax impacts) included in AOCI (in the tables above), that have not yet been recognized in net periodic benefit cost: (Thousands of dollars) September 30, 2024 December 31, 2023 Net actuarial loss $ (356,238) $ (361,968) Prior service cost (1,046) (1,178) Less: amount recognized in regulatory assets 305,451 309,794 Recognized in AOCI $ (51,833) $ (53,352)

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
Segment Information (Tables)	Sep. 30, 2024
Segment Reporting [Abstract]
Schedule of Accounts Receivable for Services	Accounts receivable for these services, which are not eliminated during consolidation, are presented in the table below: (Thousands of dollars) September 30, 2024 December 31, 2023 Centuri accounts receivable for services provided to Southwest $ 7,330 $ 13,017
Schedule of Segment Reporting Information	The financial information pertaining to the natural gas distribution, utility infrastructure services, and pipeline and storage segments are as follows: (Thousands of dollars) Natural Gas Utility Infrastructure Pipeline and Storage Other Total Three Months Ended September 30, 2024 Revenues from external customers $ 359,131 $ 692,822 $ — $ — $ 1,051,953 Intersegment revenues — 27,231 — — 27,231 Total $ 359,131 $ 720,053 $ — $ — $ 1,079,184 Segment net income (loss) $ 572 $ 9,956 $ — $ (10,239) $ 289 Three Months Ended September 30, 2023 Revenues from external customers $ 394,603 $ 745,639 $ — $ — $ 1,140,242 Intersegment revenues — 29,250 — — 29,250 Total $ 394,603 $ 774,889 $ — $ — $ 1,169,492 Segment net income (loss) $ (3,251) $ 17,956 $ — $ (11,474) $ 3,231 (Thousands of dollars) Natural Gas Utility Infrastructure Pipeline and Storage Other Total Nine Months Ended September 30, 2024 Revenues from external customers $ 1,922,157 $ 1,840,961 $ — $ — $ 3,763,118 Intersegment revenues — 79,190 — — 79,190 Total $ 1,922,157 $ 1,920,151 $ — $ — $ 3,842,308 Segment net income (loss) $ 163,991 $ (21,220) $ — $ (36,412) $ 106,359 Nine Months Ended September 30, 2023 Revenues from external customers $ 1,797,348 $ 2,145,601 $ 35,132 $ — $ 3,978,081 Intersegment revenues — 88,360 — — 88,360 Total $ 1,797,348 $ 2,233,961 $ 35,132 $ — $ 4,066,441 Segment net income (loss) $ 150,565 $ 24,902 $ (16,288) $ (81,159) $ 78,020

Centuri Separation (Tables)

Centuri Separation (Tables)	9 Months Ended
Centuri Separation (Tables)	Sep. 30, 2024
Discontinued Operations and Disposal Groups [Abstract]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest	The following reflects the effects of changes in the Company’s ownership interest in Centuri on the Company’s equity: Nine Months Ended (Thousands of dollars) 2024 Net income attributable to Southwest Gas Holdings, Inc. $ 106,359 Increase in additional paid-in capital as a result of Centuri IPO 154,287 Change from net income attributable to Southwest Gas Holdings, Inc. and transfers from noncontrolling interest $ 260,646

Background, Organization, and_4

Background, Organization, and Summary of Significant Accounting Policies - Narrative (Details) - USD ($)		1 Months Ended		3 Months Ended				9 Months Ended		12 Months Ended
	Oct. 15, 2024	Apr. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Apr. 30, 2024	Mar. 31, 2022	Nov. 30, 2018
Significant Accounting Policies [Line Items]
Net cost of gas sold				$ (111,712,000)		$ (170,056,000)		$ (984,188,000)	$ (908,646,000)
Increase in deferred purchased gas costs								(732,600,000)	252,022,000
Current assets held for sale				0				0		$ 21,377,000
Other property and investments adjustment				(1,193,062,000)				(1,193,062,000)		(1,266,340,000)
Capital expenditures incurred but not yet paid, increase (decrease)								(28,100,000)	(39,600,000)
Goodwill impairment loss								0
Dividends declared but not yet paid				44,500,000				44,500,000		44,400,000
Accrued purchased gas cost				33,500,000				33,500,000		87,600,000
Deferred gas cost, net				$ (180,000,000)		$ 687,000,000		(180,000,000)	687,000,000
Percentage of redeemable noncontrolling interest redeemed			5%
Redemption of redeemable noncontrolling interest								$ 92,839,000	$ 39,894,000
Effective income tax rate				(421.10%)		(47.10%)		14.80%	28.20%
Subsequent Event
Significant Accounting Policies [Line Items]
Amended cooperation agreement term, period prior to expiration of advance notice deadline	30 days
Amended cooperation agreement, annual meeting time period	30 days
Money Market Funds
Significant Accounting Policies [Line Items]
Money market fund investments				$ 173,400,000				$ 173,400,000		48,900,000
Certain Assets Associated With Previous Corporate Headquarters
Significant Accounting Policies [Line Items]
Current assets held for sale			$ 27,000,000				$ 27,000,000
Other property and investments adjustment			$ 27,000,000				27,000,000
Estimated loss on disposition of assets										5,200,000
Revision of Prior Period, Error Correction, Adjustment
Significant Accounting Policies [Line Items]
Net cost of gas sold											$ 5,700,000	$ 2,300,000
Increase in deferred purchased gas costs							8,000,000
Decrease in net cost of gas sold							8,000,000
Loss on disposal adjustment							21,000,000
Impairment of asset held for sale adjustment							$ 21,000,000
prime rate \| Promissory Note
Significant Accounting Policies [Line Items]
Debt, basis spread on variable rate								2%
Centuri
Significant Accounting Policies [Line Items]
Ownership percentage by parent													81%
Drum
Significant Accounting Policies [Line Items]
Ownership percentage by noncontrolling owners				0.81%				0.81%
Centuri
Significant Accounting Policies [Line Items]
Redemption of redeemable noncontrolling interest		$ 39,900,000
Centuri \| Drum
Significant Accounting Policies [Line Items]
Percentage of equity interest exchanged with debt forgiveness					0.47%
Equity ownership, percentage purchased					0.13%
Payments to acquire additional interest					$ 800,000
Centuri \| Drum
Significant Accounting Policies [Line Items]
Ownership percentage by parent				99%				99%
Southwest Gas Corporation
Significant Accounting Policies [Line Items]
Net cost of gas sold				$ (111,712,000)		$ (170,056,000)		$ (984,188,000)	$ (902,278,000)
Increase in deferred purchased gas costs								(732,599,000)	237,017,000
Current assets held for sale				0				0		21,376,000
Other property and investments adjustment				(159,174,000)				(159,174,000)		(152,658,000)
Capital expenditures incurred but not yet paid, increase (decrease)								(17,000,000)	$ (35,200,000)
Gas pipe materials and operating supplies				$ 77,500,000				$ 77,500,000		83,400,000
Effective income tax rate				113%		65.30%		14.20%	12.90%
Southwest Gas Corporation \| Money Market Funds
Significant Accounting Policies [Line Items]
Money market fund investments				$ 141,700,000				$ 141,700,000		$ 38,600,000
Previous Owner Of Linetec \| Linetec
Significant Accounting Policies [Line Items]
Ownership percentage by noncontrolling owners		10%			10%									15%	20%
Current partial redemption transpired					$ 92,000,000
Certain Members Of Riggs Distler Management \| Drum
Significant Accounting Policies [Line Items]
Ownership percentage by noncontrolling owners				1.41%				1.41%
Discontinued Operations, Disposed of by Sale \| MountainWest
Significant Accounting Policies [Line Items]
Ownership percentage disposed											100%
Disposal consideration											$ 1,500,000,000

Background, Organization, and_5

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Other Property and Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Other property and investments	$ 41,121	$ 37,220
Non-regulated property, equipment, and intangibles	1,718,709	1,752,094
Non-regulated accumulated provision for depreciation and amortization	(725,942)	(675,632)
Total	1,193,062	1,266,340
Southwest Gas Corporation
Property, Plant and Equipment [Line Items]
Net cash surrender value of COLI policies	154,673	146,546
Other property and investments	4,501	6,112
Total	$ 159,174	$ 152,658

Background, Organization, and_6

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 789,729
Foreign currency translation adjustment	(2,134)
Goodwill, ending balance	787,595
Natural Gas Distribution
Goodwill [Roll Forward]
Goodwill, beginning balance	11,155
Foreign currency translation adjustment	0
Goodwill, ending balance	11,155
Utility Infrastructure Services
Goodwill [Roll Forward]
Goodwill, beginning balance	778,574
Foreign currency translation adjustment	(2,134)
Goodwill, ending balance	$ 776,440

Background, Organization, and_7

Background, Organization, and Summary of Significant Accounting Policies - Other Income (Deductions) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Other income (deductions)
Total other income (deductions)	$ 16,758	$ 14,464	$ 49,818	$ 52,528
Corporate and administrative
Other income (deductions)
Total other income (deductions)	(66)	(183)	(57)	66
Southwest Gas Corporation
Other income (deductions)
Change in COLI policies	3,200	(1,500)	7,800	4,800
Interest income	8,736	13,249	27,649	40,235
Equity AFUDC	1,874	0	5,548	0
Other components of net periodic benefit cost	4,131	5,097	12,392	15,290
Miscellaneous income and (expense)	(1,276)	(2,309)	(4,413)	(8,603)
Total other income (deductions)	16,665	14,537	48,976	51,722
Centuri, MountainWest And Southwest Gas Holdings, Inc.
Other income (deductions)
Foreign transaction gain (loss)	(5)	18	(6)	(399)
Equity AFUDC	0	0	0	82
Equity in earnings (loss) of unconsolidated investments	127	142	(30)	591
Miscellaneous income and (expense)	$ 37	$ (50)	$ 935	$ 466

Background, Organization, and_8

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Redeemable Noncontrolling Interest (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($)
Movement In Redeemable Noncontrolling Interest [Roll Forward]
Redeemable noncontrolling interest, beginning balance	$ 104,667
Net income (loss) attributable to redeemable noncontrolling interests	(130)
Redemption value adjustments	194
Redemption of redeemable noncontrolling interest	(97,025)
Redeemable noncontrolling interest, ending balance	7,706
Linetec
Movement In Redeemable Noncontrolling Interest [Roll Forward]
Redeemable noncontrolling interest, beginning balance	91,978
Net income (loss) attributable to redeemable noncontrolling interests	(193)
Redemption value adjustments	194
Redemption of redeemable noncontrolling interest	(91,979)
Redeemable noncontrolling interest, ending balance	0
Drum
Movement In Redeemable Noncontrolling Interest [Roll Forward]
Redeemable noncontrolling interest, beginning balance	12,689
Net income (loss) attributable to redeemable noncontrolling interests	63
Redemption value adjustments	0
Redemption of redeemable noncontrolling interest	(5,046)
Redeemable noncontrolling interest, ending balance	$ 7,706

Background, Organization, and_9

Background, Organization, and Summary of Significant Accounting Policies - Schedule of Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Weighted average basic shares (in shares)	71,880	71,626	71,816	70,488
Effect of dilutive securities:
Restricted stock units (in shares)	206	225	178	188
Weighted average diluted shares (in shares)	72,086	71,851	71,994	70,676
Number of performance share units granted (in shares)	165	189	148	160

Components of Net Periodic Be_3

Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Qualified Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7,063	$ 6,460	$ 21,189	$ 19,380
Interest cost	15,097	14,791	45,291	44,373
Expected return on plan assets	(21,953)	(21,015)	(65,859)	(63,045)
Amortization of net actuarial loss	1,577	84	4,731	252
Net periodic benefit cost	1,784	320	5,352	960
SERP
Defined Benefit Plan Disclosure [Line Items]
Service cost	61	62	183	186
Interest cost	542	531	1,626	1,593
Amortization of net actuarial loss	333	249	999	748
Net periodic benefit cost	936	842	2,808	2,527
PBOP
Defined Benefit Plan Disclosure [Line Items]
Service cost	322	317	966	951
Interest cost	794	825	2,383	2,475
Expected return on plan assets	(565)	(606)	(1,695)	(1,818)
Amortization of prior service costs	44	44	132	132
Net periodic benefit cost	$ 595	$ 580	$ 1,786	$ 1,740

Revenue - Schedule of Regulated

Revenue - Schedule of Regulated Operations Revenues: Natural Gas Distribution Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Total Regulated operations revenues	$ 359,131	$ 394,603	$ 1,922,157	$ 1,832,480
Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	321,391	369,093	1,892,245	1,857,774
Alternative revenue program revenues (deferrals)	34,341	21,840	17,978	(72,251)
Other revenues	3,399	3,670	11,934	11,825
Total Regulated operations revenues	359,131	394,603	1,922,157	1,797,348
Residential \| Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	189,156	215,376	1,283,945	1,277,363
Small commercial \| Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	70,708	85,955	387,793	366,667
Large commercial \| Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20,569	27,888	87,895	84,021
Industrial/other \| Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13,443	16,596	49,737	52,165
Transportation \| Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 27,515	$ 23,278	$ 82,875	$ 77,558

Revenue - Schedule of Regulat_2

Revenue - Schedule of Regulated Operations Revenues: Utility Infrastructure Services Segment (Details) - Centuri - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 720,053	$ 774,889	$ 1,920,151	$ 2,233,961
Master services agreement
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	569,000	631,913	1,571,701	1,830,242
Bid contract
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	151,053	142,976	348,450	403,719
Unit price contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	412,871	440,787	1,119,161	1,191,889
Fixed price contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	138,242	165,637	383,090	521,722
Time and materials contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	168,940	168,465	417,900	520,350
Gas infrastructure services
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	416,424	450,335	1,059,326	1,188,941
Gas infrastructure services \| Previously Reported
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		443,083		1,173,960
Electric power infrastructure services
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	300,510	314,850	845,699	1,008,911
Electric power infrastructure services \| Previously Reported
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		200,547		668,681
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 3,119	9,704	$ 15,126	36,109
Other \| Previously Reported
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		$ 131,259		$ 391,320

Revenue - Summary of Informatio

Revenue - Summary of Information about Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Contracts receivable, net	$ 253,019	$ 347,454
Revenue earned on contracts in progress in excess of billings	288,568	269,808
Amounts billed in excess of revenue earned on contracts	$ 21,894	$ 43,694

Revenue - Narrative (Details)

Revenue - Narrative (Details) $ in Millions	1 Months Ended	9 Months Ended
Revenue - Narrative (Details) $ in Millions	Sep. 30, 2024 USD ($) contract	Sep. 30, 2024 USD ($) contract	Dec. 31, 2023 USD ($)
Segment Reporting Information [Line Items]
Contract assets increase (decrease)	$ 24.1	$ 24.1	$ 0.2
Decrease of contract liability		$ 21.8
Centuri
Segment Reporting Information [Line Items]
Number of contracts with original duration more than one year \| contract	42	42
Accounts receivable securitization term (in years)	3 years
Accounts receivable securitization, maximum amount authorized	$ 125	$ 125
Accounts receivable from securitization	125	125
Unsold accounts receivable, held as collateral	60.6	60.6
Contract assets, held as collateral	115.5	115.5
Proceeds from accounts receivable securitization		125
Repayments of accounts receivable securitization		0
Accounts receivable securitization, remaining amount authorized	0	0
Centuri \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01
Segment Reporting Information [Line Items]
Transaction price allocated to unsatisfied performance obligations of contracts	$ 249.1	$ 249.1
Transaction price allocated to unsatisfied performance obligations of contracts, period	2 years	2 years

Revenue - Schedule of Utility I

Revenue - Schedule of Utility Infrastructure Services Contracts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Contracts receivable, net	$ 253,019	$ 347,454
Utility Infrastructure Services
Disaggregation of Revenue [Line Items]
Contracts receivable, gross	255,924	349,966
Allowance for doubtful accounts	(2,905)	(2,512)
Contracts receivable, net	253,019	347,454
Utility Infrastructure Services \| Billed on completed contracts and contracts in progress
Disaggregation of Revenue [Line Items]
Contracts receivable, gross	253,809	348,021
Utility Infrastructure Services \| Other receivables
Disaggregation of Revenue [Line Items]
Contracts receivable, gross	$ 2,115	$ 1,945

Common Stock (Details)

Common Stock (Details) - USD ($) shares in Thousands		9 Months Ended
Common Stock (Details) - USD ($) shares in Thousands	Aug. 06, 2024	Sep. 30, 2024
Omnibus Incentive Plan
Class of Stock [Line Items]
Common stock issued (in shares)		78
Dividend Reinvestment and Stock Purchase Plan
Class of Stock [Line Items]
Common stock issued (in shares)		98
Common stock issued, amount		$ 6,900,000
ATM Program
Class of Stock [Line Items]
Aggregate net proceeds from stock offering	$ 340,000,000

Debt - Schedule of Carrying Amo

Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Less: current maturities	$ (30,264)	$ (42,552)
Long-term debt, less current maturities	4,382,146	4,609,838
Carrying Amount
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(12,627)	(17,111)
Less: current maturities	(30,264)	(42,552)
Long-term debt, less current maturities	4,382,146	4,609,838
Southwest Gas Corporation
Debt Instrument [Line Items]
Long-term debt, less current maturities	3,503,629	3,501,543
Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Less: current maturities	0	0
Long-term debt, less current maturities	3,503,629	3,501,543
Centuri \| Carrying Amount \| Centuri secured revolving credit facility
Debt Instrument [Line Items]
Long-term debt, gross	116,378	77,121
Centuri \| Fair Value \| Centuri secured revolving credit facility
Debt Instrument [Line Items]
Long-term debt, gross	116,456	77,205
Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(27,273)	(29,594)
Long-term debt	3,305,227	3,302,906
Revolving credit facility and commercial paper \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt	0	0
Revolving credit facility and commercial paper \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt	0	0
Industrial development revenue bonds \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Unamortized discount and debt issuance costs	(1,598)	(1,363)
Long-term debt	198,402	198,637
Other debt obligations \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	73,655	96,599
Other debt obligations \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 71,584	92,209
8% Series, due 2026 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	8%
8% Series, due 2026 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 75,000	75,000
8% Series, due 2026 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 78,648	79,502
Medium-term notes, 7.92% series, due 2027 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	7.92%
Medium-term notes, 7.92% series, due 2027 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 25,000	25,000
Medium-term notes, 7.92% series, due 2027 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 26,707	26,883
Medium-term notes, 6.76% series, due 2027 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	6.76%
Medium-term notes, 6.76% series, due 2027 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 7,500	7,500
Medium-term notes, 6.76% series, due 2027 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 7,823	7,800
Notes, 5.8%, due 2027 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	5.80%
Notes, 5.8%, due 2027 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 5.8%, due 2027 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 311,610	309,180
Notes, 3.7%, due 2028 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	3.70%
Notes, 3.7%, due 2028 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 3.7%, due 2028 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 291,240	285,300
Notes, 5.45%, due 2028 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	5.45%
Notes, 5.45%, due 2028 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 5.45%, due 2028 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 309,360	307,170
Notes, 2.2%, due 2030 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	2.20%
Notes, 2.2%, due 2030 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 450,000	450,000
Notes, 2.2%, due 2030 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 398,970	382,635
Notes, 4.05%, due 2032 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	4.05%
Notes, 4.05%, due 2032 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 600,000	600,000
Notes, 4.05%, due 2032 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 570,300	563,940
Notes, 6.1%, due 2041 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	6.10%
Notes, 6.1%, due 2041 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 125,000	125,000
Notes, 6.1%, due 2041 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 134,025	126,238
Notes, 4.875%, due 2043 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	4.875%
Notes, 4.875%, due 2043 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 250,000	250,000
Notes, 4.875%, due 2043 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 225,975	214,050
Notes, 3.8%, due 2046 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	3.80%
Notes, 3.8%, due 2046 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 3.8%, due 2046 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 238,230	225,240
Notes, 4.15%, due 2049 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	4.15%
Notes, 4.15%, due 2049 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 4.15%, due 2049 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 241,830	236,370
Notes, 3.18%, due 2051 \| Debentures \| Southwest Gas Corporation
Debt Instrument [Line Items]
Debt instrument interest rate	3.18%
Notes, 3.18%, due 2051 \| Debentures \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000	300,000
Notes, 3.18%, due 2051 \| Debentures \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	200,670	197,760
Tax-exempt Series A, due 2028 \| Industrial development revenue bonds \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
Tax-exempt Series A, due 2028 \| Industrial development revenue bonds \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2003 Series A, due 2038 \| Industrial development revenue bonds \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2003 Series A, due 2038 \| Industrial development revenue bonds \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2008 Series A, due 2038 \| Industrial development revenue bonds \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2008 Series A, due 2038 \| Industrial development revenue bonds \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2009 Series A, due 2039 \| Industrial development revenue bonds \| Southwest Gas Corporation \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
2009 Series A, due 2039 \| Industrial development revenue bonds \| Southwest Gas Corporation \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	50,000	50,000
Centuri secured term loan facility \| Secured Debt \| Centuri \| Carrying Amount
Debt Instrument [Line Items]
Long-term debt, gross	731,375	994,238
Centuri secured term loan facility \| Secured Debt \| Centuri \| Fair Value
Debt Instrument [Line Items]
Long-term debt, gross	$ 727,718	$ 996,723

Debt - Narrative (Details)

Debt - Narrative (Details)			1 Months Ended	9 Months Ended
Debt - Narrative (Details)	Aug. 01, 2024	Jul. 31, 2024	Apr. 30, 2024 USD ($)	Sep. 30, 2024 USD ($)	Mar. 22, 2024	Dec. 31, 2023 USD ($)	Apr. 30, 2023 USD ($)
Debt Instrument [Line Items]
Short-term debt				$ 663,000,000		$ 628,500,000
SWH term loan facility \| Secured Debt
Debt Instrument [Line Items]
Debt instrument face amount							$ 550,000,000
$550 Million Term Loan Credit Agreement Due July 31, 2025 \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt, basis spread on variable rate	1.125%	1.30%
Centuri
Debt Instrument [Line Items]
Repayments of debt			$ 316,000,000
Centuri \| Centuri Secured Term Loan Facility And Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity				1,545,000,000
Borrowings outstanding under facility				$ 847,800,000
Centuri \| Centuri secured term loan facility \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt, basis spread on variable rate				2.50%
Centuri \| Centuri secured term loan facility \| Alternative base rate
Debt Instrument [Line Items]
Debt, basis spread on variable rate				1.50%
Centuri \| Centuri secured term loan facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity				$ 1,145,000,000
Repayments of debt			160,000,000
$400 Million Credit Facility \| Southwest Gas Corporation
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity				400,000,000
Line of credit designated as long term debt				150,000,000
Line of credit designated for working capital purposes				250,000,000
Long-term debt outstanding				0
Short-term debt				$ 0
$400 Million Credit Facility \| Southwest Gas Corporation \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt, basis spread on variable rate				1.125%
$400 Million Credit Facility \| Southwest Gas Corporation \| Alternative base rate
Debt Instrument [Line Items]
Debt, basis spread on variable rate				0.125%
Revolving Credit Facility \| Line of Credit \| Period From April 18, 2024 Through June 30, 2024
Debt Instrument [Line Items]
Debt covenant, net leverage ratio					5.25
Revolving Credit Facility \| Line of Credit \| Period From July 1, 2024 Through September 29, 2024
Debt Instrument [Line Items]
Debt covenant, net leverage ratio					5
Revolving Credit Facility \| Line of Credit \| Period From September 30, 2024 Through December 29, 2024
Debt Instrument [Line Items]
Debt covenant, net leverage ratio					4.25
Revolving Credit Facility \| Line of Credit \| Period on December 30, 2024 and Thereafter
Debt Instrument [Line Items]
Debt covenant, net leverage ratio					4
Revolving Credit Facility \| Centuri \| Line of Credit
Debt Instrument [Line Items]
Debt secured by assets				$ 2,400,000,000
Revolving Credit Facility \| Centuri \| Minimum \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt, basis spread on variable rate				1%
Revolving Credit Facility \| Centuri \| Minimum \| CORRA
Debt Instrument [Line Items]
Debt, basis spread on variable rate				0%
Revolving Credit Facility \| Centuri \| Maximum \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt, basis spread on variable rate				2.50%
Revolving Credit Facility \| Centuri \| Maximum \| CORRA
Debt Instrument [Line Items]
Debt, basis spread on variable rate				1.50%
Centuri secured revolving credit facility \| Centuri
Debt Instrument [Line Items]
Repayments of debt			$ 156,000,000
Centuri secured revolving credit facility \| Centuri \| Line of Credit
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity				$ 400,000,000
$300 Million Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum commitment amount				300,000,000
Short-term debt				$ 113,000,000

Other Comprehensive Income an_3

Other Comprehensive Income and Accumulated Other Comprehensive Income - Related Tax Effects Allocated to OCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ 2,181	$ (2,002)	$ (777)	$ 906
Other comprehensive income (loss), tax	(122)	(63)	(365)	(187)
Total other comprehensive income (loss), net of tax	2,059	(2,065)	(1,142)	719
Total other comprehensive income (loss) - noncontrolling interest, before- tax amount	(319)	0	(150)	0
Total other comprehensive income (loss) - noncontrolling interest, tax (expense) or benefit	0	0	0	0
Total other comprehensive income (loss) - noncontrolling interest, net-of- tax amount	(319)	0	(150)	0
Total other comprehensive income (loss), before- tax amount	1,862	(2,002)	(927)	906
Total other comprehensive income (loss), net-of- tax amount	(122)	(63)	(365)	(187)
Total other comprehensive income (loss), tax (expense) or benefit	$ 1,740	$ (2,065)	$ (1,292)	$ 719
Statutory income tax rate	24%	24%	24%	24%
Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ 506	$ 259	$ 1,519	$ 776
Other comprehensive income (loss), tax	(122)	(63)	(365)	(187)
Total other comprehensive income (loss), net of tax	384	196	1,154	589
Amortization of prior service cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax			132
Other comprehensive income (loss), tax			(33)
Total other comprehensive income (loss), net of tax			99
Amortization of prior service cost \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	44	44	132	132
Reclassification from AOCI, tax	(11)	(11)	(33)	(33)
Reclassification from AOCI, net of tax	33	33	99	99
Amortization of net actuarial (gain)/loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax			5,730
Other comprehensive income (loss), tax			(1,375)
Total other comprehensive income (loss), net of tax			4,355
Amortization of net actuarial (gain)/loss \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	1,910	333	5,730	1,000
Reclassification from AOCI, tax	(458)	(80)	(1,375)	(240)
Reclassification from AOCI, net of tax	1,452	253	4,355	760
Regulatory adjustment \| Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	(1,448)	(118)	(4,343)	(356)
Reclassification from AOCI, tax	347	28	1,043	86
Reclassification from AOCI, net of tax	(1,101)	(90)	(3,300)	(270)
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax	1,675	(2,261)	(2,296)	130
Other comprehensive income (loss) before reclassifications, tax	0	0	0	0
Other comprehensive income (loss) before reclassifications, net of tax	$ 1,675	$ (2,261)	(2,296)	$ 130
Total other comprehensive income (loss), before- tax amount			(1,242)
Total other comprehensive income (loss), net-of- tax amount			0
Total other comprehensive income (loss), tax (expense) or benefit			$ (1,242)

Other Comprehensive Income an_4

Other Comprehensive Income and Accumulated Other Comprehensive Income - AOCI Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ 3,310,036
Beginning balance, attributable to parent			3,310,036
Other comprehensive income (loss), before tax	$ 2,181	$ (2,002)	(777)	$ 906
Other comprehensive income (loss), tax	(122)	(63)	(365)	(187)
Total other comprehensive income (loss), net of tax	2,059	(2,065)	(1,142)	719
Less current period other comprehensive income (loss) attributable to noncontrolling interest , before- tax amount	(319)	0	(150)	0
Less current period other comprehensive income (loss) attributable to noncontrolling interest , tax (expense) or benefit	0	0	0	0
Total other comprehensive income (loss) - noncontrolling interest, net-of- tax amount	(319)	0	(150)	0
Ending balance	3,632,250	3,238,745	3,632,250	3,238,745
Ending balance, attributable to parent	3,455,393		3,455,393
Total other comprehensive income (loss), before- tax amount	1,862	(2,002)	(927)	906
Total other comprehensive income (loss), net-of- tax amount	(122)	(63)	(365)	(187)
Total other comprehensive income (loss), tax (expense) or benefit	$ 1,740	$ (2,065)	$ (1,292)	$ 719
Statutory income tax rate	24%	24%	24%	24%
Southwest Gas Corporation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, attributable to parent			$ 3,183,615
Other comprehensive income (loss), before tax	$ 506	$ 259	1,519	$ 776
Other comprehensive income (loss), tax	(122)	(63)	(365)	(187)
Total other comprehensive income (loss), net of tax	384	196	1,154	589
Ending balance	3,215,562	3,135,296	3,215,562	3,135,296
Ending balance, attributable to parent	3,215,562		3,215,562
Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, before tax			(53,352)
Beginning balance, tax (expense) benefit			12,804
Beginning balance			(40,548)
Other comprehensive income (loss), before tax			1,519
Other comprehensive income (loss), tax			(365)
Total other comprehensive income (loss), net of tax			1,154
Ending balance, before tax	(51,833)		(51,833)
Ending balance, tax (expense) benefit	12,439		12,439
Ending balance	(39,394)		(39,394)
Total other comprehensive income (loss), before- tax amount			1,519
Total other comprehensive income (loss), net-of- tax amount			(365)
Total other comprehensive income (loss), tax (expense) or benefit			1,154
Defined Benefit Plans \| Southwest Gas Corporation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, attributable to parent, before tax			(53,352)
Beginning balance, attributable to parent, tax (expense) benefit			12,804
Beginning balance, attributable to parent			(40,548)
Other comprehensive income (loss), before tax			1,519
Other comprehensive income (loss), tax			(365)
Total other comprehensive income (loss), net of tax			1,154
Ending balance, attributable to parent, before tax	(51,833)		(51,833)
Ending balance, attributable to parent, tax (expense) benefit	12,439		12,439
Ending balance, attributable to parent	(39,394)		(39,394)
Amortization of prior service cost
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before tax			132
Other comprehensive income (loss), tax			(33)
Total other comprehensive income (loss), net of tax			99
Amortization of prior service cost \| Southwest Gas Corporation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, before Tax	44	44	132	132
Reclassification from AOCI, tax	(11)	(11)	(33)	(33)
Reclassification from AOCI, net of tax	33	33	99	99
Amortization of net actuarial loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before tax			5,730
Other comprehensive income (loss), tax			(1,375)
Total other comprehensive income (loss), net of tax			4,355
Amortization of net actuarial loss \| Southwest Gas Corporation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, before Tax	1,910	333	5,730	1,000
Reclassification from AOCI, tax	(458)	(80)	(1,375)	(240)
Reclassification from AOCI, net of tax	1,452	253	4,355	760
Regulatory adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before tax			(4,343)
Other comprehensive income (loss), tax			1,043
Total other comprehensive income (loss), net of tax			(3,300)
Regulatory adjustment \| Southwest Gas Corporation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before tax			(4,343)
Other comprehensive income (loss), tax			1,043
Total other comprehensive income (loss), net of tax			(3,300)
Foreign Currency Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, before tax			(3,239)
Beginning balance, tax (expense) benefit			0
Beginning balance			(3,239)
Other comprehensive income (loss) before reclassifications, before tax			(2,296)
Other comprehensive income (loss) before reclassifications, tax			0
Other comprehensive income (loss) before reclassifications, net of tax			(2,296)
Less current period other comprehensive income (loss) attributable to noncontrolling interest , before- tax amount			(150)
Less current period other comprehensive income (loss) attributable to noncontrolling interest , tax (expense) or benefit			0
Total other comprehensive income (loss) - noncontrolling interest, net-of- tax amount			(150)
Centuri IPO, before- tax amount			1,204
Centuri IPO, tax (expense) benefit			0
Centuri IPO, After-Tax			1,204
Ending balance, before tax	(4,481)		(4,481)
Ending balance, tax (expense) benefit	0		0
Ending balance	(4,481)		(4,481)
Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Less current period other comprehensive income (loss) attributable to noncontrolling interest , before- tax amount			0
Less current period other comprehensive income (loss) attributable to noncontrolling interest , tax (expense) or benefit			0
Total other comprehensive income (loss) - noncontrolling interest, net-of- tax amount			0
Centuri IPO, before- tax amount			0
Centuri IPO, tax (expense) benefit			0
Centuri IPO, After-Tax			0
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications, net of tax			(88)
Total other comprehensive income (loss) - noncontrolling interest, net-of- tax amount			(150)
Centuri IPO, After-Tax			1,204
AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(45,615)	(41,458)	(43,787)	(44,242)
Other comprehensive income (loss) before reclassifications, net of tax			(1,142)
Ending balance	(43,875)	(43,523)	(43,875)	(43,523)
AOCI \| Southwest Gas Corporation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(39,778)	(37,868)	(40,548)	(38,261)
Ending balance	(39,394)	(37,672)	(39,394)	(37,672)
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications, before tax	1,675	(2,261)	(2,296)	130
Other comprehensive income (loss) before reclassifications, tax	0	0	0	0
Other comprehensive income (loss) before reclassifications, net of tax	$ 1,675	$ (2,261)	(2,296)	$ 130
Total other comprehensive income (loss), before- tax amount			(1,242)
Total other comprehensive income (loss), net-of- tax amount			0
Total other comprehensive income (loss), tax (expense) or benefit			$ (1,242)

Other Comprehensive Income an_5

Other Comprehensive Income and Accumulated Other Comprehensive Income - Amounts Recognized Before Tax, Defined Benefit Plans (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Equity [Abstract]
Net actuarial loss	$ (356,238)	$ (361,968)
Prior service cost	(1,046)	(1,178)
Less: amount recognized in regulatory assets	305,451	309,794
Recognized in AOCI	$ (51,833)	$ (53,352)

Segment Information - Narrative

Segment Information - Narrative (Details)	3 Months Ended		9 Months Ended
Segment Information - Narrative (Details)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) segment	Sep. 30, 2023 USD ($)	Apr. 30, 2023 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment			2
Segment Reporting Information [Line Items]
Interest expense	$ 77,731,000	$ 71,998,000	$ 223,105,000	$ 218,679,000
SWH term loan facility \| Secured Debt
Segment Reporting Information [Line Items]
Interest expense	$ 11,500,000
Debt instrument face amount					$ 550,000,000

Segment Information - Accounts

Segment Information - Accounts Receivable Not Eliminated During Consolidation (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Centuri accounts receivable for services provided to Southwest	$ 673,219	$ 886,549
Centuri \| Related Party
Segment Reporting Information [Line Items]
Centuri accounts receivable for services provided to Southwest	$ 7,330	$ 13,017

Segment Information - Schedule

Segment Information - Schedule of Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Revenues	$ 1,079,184	$ 1,169,492	$ 3,842,308	$ 4,066,441
Segment net income (loss)	289	3,231	106,359	78,020
Operating Segments
Segment Reporting Information [Line Items]
Revenues	1,051,953	1,140,242	3,763,118	3,978,081
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	(27,231)	(29,250)	(79,190)	(88,360)
Other
Segment Reporting Information [Line Items]
Segment net income (loss)	(10,239)	(11,474)	(36,412)	(81,159)
Natural Gas Distribution
Segment Reporting Information [Line Items]
Revenues	359,131	394,603	1,922,157	1,797,348
Natural Gas Distribution \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	359,131	394,603	1,922,157	1,797,348
Segment net income (loss)	572	(3,251)	163,991	150,565
Natural Gas Distribution \| Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Utility Infrastructure Services
Segment Reporting Information [Line Items]
Revenues	720,053	774,889	1,920,151	2,233,961
Utility Infrastructure Services \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	692,822	745,639	1,840,961	2,145,601
Segment net income (loss)	9,956	17,956	(21,220)	24,902
Utility Infrastructure Services \| Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	(27,231)	(29,250)	(79,190)	(88,360)
Pipeline and Storage
Segment Reporting Information [Line Items]
Revenues	0	0	0	35,132
Pipeline and Storage \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	0	0	0	35,132
Segment net income (loss)	0	0	0	(16,288)
Pipeline and Storage \| Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	$ 0	$ 0	$ 0	$ 0

Centuri Separation- Narrative (

Centuri Separation- Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total equity ending balances		$ 3,632,250	$ 3,238,745	$ 3,632,250	$ 3,238,745		$ 3,310,036
Net income attributable to noncontrolling interests		2,374	736	4,076	3,856
Noncontrolling interest
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total equity ending balances		176,857	$ 0	$ 176,857	$ 0	$ 174,199	$ 0	$ 0	$ 0
Net income attributable to noncontrolling interests		$ 2,300
Centuri
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership percentage by parent	81%
Centuri
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayments of debt	$ 316,000
IPO, Excluding Over-Allotment Option \| Centuri
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of stock, number of shares (in shares)	12,400,000
IPO \| Centuri
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of stock, price per share (in USD per share)	$ 21
Period of option to purchase for underwriters	30 days
Stock issuance costs	$ 18,000
Net proceeds from sale of stock	$ 328,000
Over-Allotment Option \| Centuri
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of stock, number of shares (in shares)	1,860,000
Over-Allotment Option \| Centuri \| Ichan Partners LP & Ichan Partners Master Fund LP
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of stock, number of shares (in shares)	2,591,929

Centuri Separation - Schedule o

Centuri Separation - Schedule of Ownership Interests (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net income attributable to Southwest Gas Holdings, Inc.	$ 289	$ 3,231	$ 106,359	$ 78,020
Change from net income attributable to Southwest Gas Holdings, Inc. and transfers from noncontrolling interest			260,646
Additional paid-in capital
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Increase in additional paid-in capital as a result of Centuri IPO	$ 5,284	$ 5,536	14,694	$ 252,576
Additional paid-in capital \| IPO
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Increase in additional paid-in capital as a result of Centuri IPO			$ 154,287