Derivative Instruments Gains (Loss) on Derivatives Recognized in Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Financial Swaps | Operating revenues
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	$ 2,609	$ 5,042	$ 3,621	$ 3,963
Financial Swaps | Purchased power
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	(1,478)	(1,733)	(525)	(107)
Financial Swaps | Operating Expense
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	(1,127)	(11,422)	(25,185)	12,114
Forward contracts | Operating revenues
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	272	1,075	1,278	1,710
Forward contracts | Purchased power
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	(690)	(1,449)	(1,681)	(2,049)
Forward contracts | Operating Expense
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss) on Derivative, Net	[1]	$ 0	$ (19)	$ (221)	$ (439)

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