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									45,911	134,696
Share-based compensation						1,950				(287)
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.									(44,635)	(39,600)
Ending balance (in shares) at Mar. 31, 2023			71,331,000	47,482,000
Ending balance at Mar. 31, 2023		$ 2,666,130	$ 72,961	$ 49,112	2,524,631	1,624,919	(43,949)	(38,065)	742,513	1,030,164
Beginning balance (in shares) at Dec. 31, 2023	71,563,750		71,564,000	47,482,000
Beginning balance at Dec. 31, 2023			$ 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									87,737	135,825
Share-based compensation						(259)				(327)
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.									(44,699)	(41,699)
Ending balance (in shares) at Mar. 31, 2024	71,665,592		71,665,000	47,482,000
Ending balance at Mar. 31, 2024		$ 3,277,539	$ 73,295	$ 49,112	$ 2,547,485	$ 2,156,318	$ (46,222)	$ (40,164)	$ 781,683	$ 1,112,273