Derivatives And Hedging (Schedule Of Derivative Instruments On The Statement Of Revenues, Expenses, And Patronage Capital) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Regulatory Asset/Liability for Derivatives	$ 3,799	$ (18,989)
Amount Of Gain (Loss) Reclassified from Regulatory Asset/Liability into Income	(753)	(25,051)
Natural Gas Future Contracts [Member] | Fuel [Member] | Operating Expense Fuel [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Regulatory Asset/Liability for Derivatives	3,711	(19,521)
Amount Of Gain (Loss) Reclassified from Regulatory Asset/Liability into Income	(4,365)	(21,466)
Financial Transmission Rights [Member] | Purchased Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Regulatory Asset/Liability for Derivatives	88	532
Amount Of Gain (Loss) Reclassified from Regulatory Asset/Liability into Income	$ 3,612	$ (3,585)