Background, Organization, and Summary of Significant Accounting Policies - Schedule of Other Property and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Other property	$ 37,220	$ 31,075
Other property and investments	1,266,340	1,281,172
Non-regulated property, equipment, and intangibles	1,752,094	1,677,218
Non-regulated accumulated provision for depreciation and amortization	(675,632)	(596,518)
Southwest Gas Corporation
Property, Plant and Equipment [Line Items]
Net cash surrender value of COLI policies	146,546	136,245
Other property	6,112	33,152
Other property and investments	$ 152,658	$ 169,397