CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Common stock shares	Additional paid-in capital	Accumulated other comprehensive loss	Retained earnings	Southwest Gas Holdings, Inc.
Beginning balance (in shares) at Dec. 31, 2020		57,193,000
Beginning balance at Dec. 31, 2020		$ 58,823	$ 1,609,155	$ (61,003)	$ 1,067,978
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)		3,186,000
Common stock issuances		$ 3,186	214,734
Foreign currency exchange translation adjustment				(324)
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax				4,136
FSIRS amounts reclassified to net income, net of tax	$ 1,240			1,240
Net income (loss)					130,836
Dividends declared					(106,303)
Redemption value adjustments					(12,642)
Ending balance (in shares) at Sep. 30, 2021		60,379,000
Ending balance at Sep. 30, 2021		$ 62,009	1,823,889	(55,951)	1,079,869	$ 2,909,816
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 1.785
Beginning balance (in shares) at Jun. 30, 2021		59,088,000
Beginning balance at Jun. 30, 2021		$ 60,718	1,733,572	(55,688)	1,108,279
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)		1,291,000
Common stock issuances		$ 1,291	90,317
Foreign currency exchange translation adjustment				(2,056)
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax				1,380
FSIRS amounts reclassified to net income, net of tax	$ 413			413
Net income (loss)					(11,576)
Dividends declared					(36,098)
Redemption value adjustments					19,264
Ending balance (in shares) at Sep. 30, 2021		60,379,000
Ending balance at Sep. 30, 2021		$ 62,009	1,823,889	(55,951)	1,079,869	2,909,816
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 0.595
FSIRS amounts reclassified to net income, net of tax	$ 828
Ending balance (in shares) at Sep. 30, 2022	67,063,730	67,064,000
Ending balance at Sep. 30, 2022		$ 68,694	2,283,250	(50,232)	1,111,203	3,412,915
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	(46,761)	1,114,313
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)		6,642,000
Common stock issuances		$ 6,642	459,034
Foreign currency exchange translation adjustment				(7,263)
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax				3,376
FSIRS amounts reclassified to net income, net of tax	$ 416			416
Net income (loss)					77,294
Dividends declared					(125,337)
Redemption value adjustments	$ (44,933)				44,933
Ending balance (in shares) at Sep. 30, 2022	67,063,730	67,064,000
Ending balance at Sep. 30, 2022		$ 68,694	2,283,250	(50,232)	1,111,203	3,412,915
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 1.86
Beginning balance (in shares) at Jun. 30, 2022		67,004,000
Beginning balance at Jun. 30, 2022		$ 68,634	2,279,493	(45,528)	1,156,253
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issuances (in shares)		60,000
Common stock issuances		$ 60	3,757
Foreign currency exchange translation adjustment				(5,830)
Net actuarial gain arising during period, less amortization of unamortized benefit plan cost, net of tax				1,126
FSIRS amounts reclassified to net income, net of tax	$ 0			0
Net income (loss)					(12,309)
Dividends declared					(41,696)
Redemption value adjustments					8,955
Ending balance (in shares) at Sep. 30, 2022	67,063,730	67,064,000
Ending balance at Sep. 30, 2022		$ 68,694	$ 2,283,250	$ (50,232)	$ 1,111,203	$ 3,412,915
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share (in USD per share)	$ 0.62