Revenue - Schedule of Regulated Operations Revenues: Natural Gas Distribution Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Total Regulated operations revenues	$ 1,052,933	$ 950,011
Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,078,208	996,245
Alternative revenue program revenues (deferrals)	(29,433)	(86,204)
Other revenues	4,158	4,838
Total Regulated operations revenues	1,052,933	914,879
Residential | Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	784,237	739,313
Small commercial | Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	206,445	174,184
Large commercial | Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	38,016	31,091
Industrial/other | Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20,823	21,114
Transportation | Southwest Gas Corporation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 28,687	$ 30,543