Fair Value - Schedule of Activity For Energy Commodity Derivative Assets (Liabilities) Measured At Fair Value Using Significant Unobservable Inputs (Level 3) (Details) - Natural Gas Exchange Agreements [Member] - Level 3 [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ (6,078)	$ (2,628)	$ (8,410)	$ (2,976)
Included in regulatory assets/liabilities	(4,971)	(1,046)	(1,482)	(952)
Settlements	0	0	(1,157)	254
Ending Balance	$ (11,049)	$ (3,674)	$ (11,049)	$ (3,674)