Background, Organization, and Summary of Significant Accounting Policies - Other Income (Deductions) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Other income (deductions)
Total other income (deductions)	$ 18,121	$ 18,460
Corporate and administrative
Other income (deductions)
Total other income (deductions)	(11)	270
Southwest Gas Corporation
Other income (deductions)
Change in COLI policies	3,600	2,400
Interest income	9,776	12,471
Equity AFUDC	1,839	0
Other components of net periodic benefit cost	4,131	4,959
Miscellaneous income and (expense)	(1,246)	(1,387)
Total other income (deductions)	18,100	18,443
Centuri, MountainWest And Southwest Gas Holdings, Inc.
Other income (deductions)
Foreign transaction gain (loss)	102	(690)
Equity AFUDC	0	82
Equity in earnings (loss) of unconsolidated investments	(113)	360
Miscellaneous income and (expense)	$ 43	$ (5)