CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - Southwest - USD ($) $ in Thousands	Total	Southwest Gas Corporation	Southwest Gas Holdings, Inc. Common Stock, $1 Par Value	Southwest Gas Holdings, Inc. Common Stock, $1 Par Value 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, 2020			57,193,000
Beginning balance at Dec. 31, 2020			$ 58,823		$ 1,609,155	$ 1,410,345	$ (61,003)	$ (61,135)	$ 1,067,978	$ 835,146
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation						2,015				(350)
Contributions from Southwest Gas Holdings, Inc.						45,984
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax							1,379	1,379
FSIRS amounts reclassified to net income, net of tax	$ 413	$ 413					413	413
Net income									117,293	118,715
Dividends declared to Southwest Gas Holdings, Inc.									(34,876)	(27,500)
Ending balance (in shares) at Mar. 31, 2021			57,995,000	47,482,000
Ending balance at Mar. 31, 2021		2,374,124	$ 59,625	$ 49,112	1,660,108	1,458,344	(58,388)	(59,343)	1,112,377	926,011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
FSIRS amounts reclassified to net income, net of tax	$ 1,655	1,655
Ending balance (in shares) at Mar. 31, 2022	66,849,225		66,849,000	47,482,000
Ending balance at Mar. 31, 2022		2,611,534	$ 68,479	$ 49,112	2,273,837	1,620,616	(43,972)	(45,371)	1,190,738	987,177
Beginning balance (in shares) at Dec. 31, 2021	60,422,081		60,422,000
Beginning balance at Dec. 31, 2021			$ 62,052		1,824,216	1,618,911	(46,761)	(46,913)	1,114,313	906,827
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation						1,705				(445)
Contributions from Southwest Gas Holdings, Inc.						0
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax							1,126	1,126
FSIRS amounts reclassified to net income, net of tax	$ 416	416					416	416
Net income									96,178	111,795
Dividends declared to Southwest Gas Holdings, Inc.									(41,909)	(31,000)
Ending balance (in shares) at Mar. 31, 2022	66,849,225		66,849,000	47,482,000
Ending balance at Mar. 31, 2022		$ 2,611,534	$ 68,479	$ 49,112	$ 2,273,837	$ 1,620,616	$ (43,972)	$ (45,371)	$ 1,190,738	$ 987,177