Derivatives And Hedging (Schedule Of Fair Value Of Derivative Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Total derivatives in an asset position	$ 5,145	$ 3,478
Total derivatives in a liability position	1,409	6,406
Natural Gas Future Contracts [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Total derivatives in an asset position	5,057	2,062
Natural Gas Future Contracts [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Total derivatives in a liability position	1,409	6,406
Financial Transmission Rights [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Total derivatives in an asset position	$ 88	$ 1,416