Derivative Instruments Gains (Loss) on Derivatives Recognized in Income (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Financial Swaps | Operating revenues
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	$ (1,079)	$ 582
Financial Swaps | Purchased power
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	1,626	116
Financial Swaps | Operating Expense
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	23,537	1,460
Forward contracts | Operating revenues
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	636	179
Forward contracts | Purchased power
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	(600)	(179)
Forward contracts | Operating Expense
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	$ (420)	$ (54)

[1] Excludes unrealized gains or losses on derivatives, which are recorded on the balance sheet as regulatory assets or regulatory liabilities.