Other Comprehensive Income and Accumulated Other Comprehensive Income - Related Tax Effects Allocated to OCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ (645)	$ 2,553	$ (2,958)	$ 2,908
Other comprehensive income (loss), tax	(121)	(62)	(243)	(124)
Total other comprehensive income (loss), net of tax	(766)	2,491	(3,201)	2,784
Total other comprehensive income (loss) - noncontrolling interest, before- tax amount	169	0	169	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	169	0	169	0
Total other comprehensive income (loss), before- tax amount	(476)	2,553	(2,789)	2,908
Total other comprehensive income (loss), net-of- tax amount	(121)	(62)	(243)	(124)
Total other comprehensive income (loss), tax (expense) or benefit	$ (597)	$ 2,491	$ (3,032)	$ 2,784
Statutory income tax rate	24.00%	24.00%	24.00%	24.00%
Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ 507	$ 259	$ 1,013	$ 517
Other comprehensive income (loss), tax	(121)	(62)	(243)	(124)
Total other comprehensive income (loss), net of tax	386	197	770	393
Amortization of prior service cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax			88
Other comprehensive income (loss), tax			(22)
Total other comprehensive income (loss), net of tax			66
Amortization of prior service cost | Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	44	44	88	88
Reclassification from AOCI, tax	(11)	(11)	(22)	(22)
Reclassification from AOCI, net of tax	33	33	66	66
Amortization of net actuarial (gain)/loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax			3,820
Other comprehensive income (loss), tax			(917)
Total other comprehensive income (loss), net of tax			2,903
Amortization of net actuarial (gain)/loss | Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	1,910	334	3,820	667
Reclassification from AOCI, tax	(458)	(80)	(917)	(160)
Reclassification from AOCI, net of tax	1,452	254	2,903	507
Regulatory adjustment | Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	(1,447)	(119)	(2,895)	(238)
Reclassification from AOCI, tax	348	29	696	58
Reclassification from AOCI, net of tax	(1,099)	(90)	(2,199)	(180)
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax	(1,152)	2,294	(3,971)	2,391
Other comprehensive income (loss) before reclassifications, tax	0	0	0	0
Other comprehensive income (loss) before reclassifications, net of tax	$ (1,152)	$ 2,294	(3,971)	$ 2,391
Total other comprehensive income (loss), before- tax amount			(2,598)
Total other comprehensive income (loss), net-of- tax amount			0
Total other comprehensive income (loss), tax (expense) or benefit			$ (2,598)