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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ (6,201)	$ (2,253)	$ (8,410)	$ (2,976)
Included in regulatory assets/liabilities	268	(391)	3,488	94
Settlements	(145)	16	(1,156)	254
Ending Balance	$ (6,078)	$ (2,628)	$ (6,078)	$ (2,628)