Derivative Accounting - Gains and Losses from Derivative Instruments (Details) - Commodity Contracts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Designated as Hedging Instruments
Derivative Instruments in Designated Cash Flows Hedges
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income on Discontinuation	$ 0	$ 0	$ 0
Fuel and purchased power | Not Designated as Hedging Instruments
Derivative Instruments Not Designated as Cash Flows Hedges
Net Gain (Loss) Recognized in Income	307,287	216,847	(3,178)
Fuel and purchased power | Designated as Hedging Instruments
Derivative Instruments in Designated Cash Flows Hedges
Loss reclassified from accumulated other comprehensive income into income (effective portion realized)	$ 0	$ 0	$ (763)