Other Comprehensive Income and Accumulated Other Comprehensive Income - Related Tax Effects Allocated to OCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ (2,313)	$ 355
Other comprehensive income (loss), tax	(122)	(62)
Total other comprehensive income (loss), net of tax	$ (2,435)	$ 293
Statutory income tax rate	24.00%	24.00%
Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ 506	$ 258
Other comprehensive income (loss), tax	(122)	(62)
Total other comprehensive income (loss), net of tax	384	196
Amortization of prior service cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	44
Other comprehensive income (loss), tax	(11)
Total other comprehensive income (loss), net of tax	33
Amortization of prior service cost | Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	44	44
Reclassification from AOCI, tax	(11)	(11)
Reclassification from AOCI, net of tax	33	33
Amortization of net actuarial (gain)/loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	1,910
Other comprehensive income (loss), tax	(459)
Total other comprehensive income (loss), net of tax	1,451
Amortization of net actuarial (gain)/loss | Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	1,910	333
Reclassification from AOCI, tax	(459)	(80)
Reclassification from AOCI, net of tax	1,451	253
Regulatory adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	(1,448)
Other comprehensive income (loss), tax	348
Total other comprehensive income (loss), net of tax	(1,100)
Regulatory adjustment | Southwest Gas Corporation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, before Tax	(1,448)	(119)
Reclassification from AOCI, tax	348	29
Reclassification from AOCI, net of tax	(1,100)	(90)
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, before tax	(2,819)	97
Other comprehensive income (loss) before reclassifications, tax	0	0
Other comprehensive income (loss) before reclassifications, net of tax	$ (2,819)	$ 97