Purchased Gas Adjustment Mechanism (Details) - USD ($) $ in Thousands			12 Months Ended
	Nov. 01, 2021	Nov. 01, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Other regulatory assets			$ 815,058	$ 747,651
Subsidiaries [Member]
Regulatory Assets [Line Items]
Other regulatory assets			815,058	747,651
PGA payable			57,935	87,655	$ 132,766
Subsidiaries [Member] | Purchased Gas Adjustment [Member]
Regulatory Assets [Line Items]
Annual revenue		$ 37,400
Out of Cycle PGA	$ 69,400	69,400
Purchased natural gas costs			364,775	314,792
Purchased natural gas costs, recoverable			(396,236)	(363,886)
Purchased natural gas adjustment, interest			$ 1,741	$ 3,983
Public Utilities, Approved Rate Increase (Decrease), Amount	59,100	$ 32,600
Subsidiaries [Member] | Schedule 101
Regulatory Assets [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	80,600
Subsidiaries [Member] | Schedule 106
Regulatory Assets [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ (21,500)