CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (11,318)	$ (9,294)	$ 79,851	$ 136,025	$ 151,028	$ 241,061
Defined benefit pension plans:
Net actuarial gain (loss)	0	0	0	0	44,974	(43,730)
Amortization of prior service cost	34	183	100	547	282	766
Amortization of net actuarial loss	6,616	8,474	19,847	25,420	28,321	32,608
Regulatory adjustment	(5,524)	(7,277)	(16,571)	(21,831)	(61,767)	2,959
Net defined benefit pension plans	1,126	1,380	3,376	4,136	11,810	(7,397)
Forward-starting interest rate swaps (“FSIRS”):
Amounts reclassified into net income (loss)	0	413	416	1,240	828	1,653
Net forward-starting interest rate swaps	0	413	416	1,240	828	1,653
Foreign currency translation adjustments	(5,830)	(2,056)	(7,263)	(324)	(6,919)	2,576
Total other comprehensive income (loss), net of tax	(4,704)	(263)	(3,471)	5,052	5,719	(3,168)
Comprehensive income (loss)	(16,022)	(9,557)	76,380	141,077	156,747	237,893
Comprehensive income attributable to noncontrolling interests	991	2,282	2,557	5,189	3,791	6,681
Comprehensive income (loss) attributable to Southwest Gas Holdings, Inc.	$ (17,013)	$ (11,839)	$ 73,823	$ 135,888	$ 152,956	$ 231,212