Summary Of Significant Accounting Policies - (Schedule of Operating Revenues) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Energy revenues	$ 540,423	$ 328,045	$ 375,714
Renewable energy credits	259	36	33
Demand revenues	410,437	398,819	395,067
Total revenues from sales to member distribution cooperatives	951,119	726,900	770,814
Energy revenues	42,818	45,255	31,431
Renewable energy credits	11,980	8,485	5,438
Demand revenues			21
Total revenues from sales to non-members	54,798	53,740	36,890
Total operating revenues	$ 1,005,917	$ 780,640	$ 807,704
Revenue, Product and Service [Extensible Enumeration]	us-gaap:ElectricityMember	us-gaap:ElectricityMember	us-gaap:ElectricityMember