Investments (Schedule Of Investments) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Schedule of Invested Securities [Line Items]
Equity, Cost	$ 2,146	$ 2,145
Equity Method Investment Gross Unrealized Gains	2,372	2,340
Equity, Fair Value	4,518	4,485
Other, Cost	2,278	2,277
Other Gross Unrealized Gains	2,411	2,374
Other, Fair Value	4,689	4,651
Total Other	2,317	2,311
Total Investments	252,607	244,648
Total Nuclear Decommissioning Trust	250,290	242,337
Nuclear Decommissioning Trust [Member]
Schedule of Invested Securities [Line Items]
Investments, Debt securities, Cost	68,197	66,727
Investments, Debt securities, Gross Unrealized Gains	4,188	7,493
Investments, Debt securities	72,385	74,220
Investments, Equity securities, Cost	92,567	89,472
Investments, Equity securities, Gross Unrealized Gains	84,694	76,828
Investments, Equity securities	177,261	166,300
Investments, Cash and other	644	1,817
Investments, Cost	161,408	158,016
Investments, Gross Unrealized Gains	88,882	84,321
Total Nuclear Decommissioning Trust	250,290	242,337
Other [Member]
Schedule of Invested Securities [Line Items]
Investments, Equity securities, Cost	132	132
Investments, Equity securities, Gross Unrealized Gains	39	34
Total Investments	$ 171	$ 166