Wholesale Power Contracts (Schedule Of Revenues From Member Distribution Cooperatives) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Member distribution revenue	$ 726.9	$ 770.8	$ 898.5
Rappahannock Electric Cooperative [Member]
Related Party Transaction [Line Items]
Member distribution revenue	223.3	237.6	279.7
Shenandoah Valley Electric Cooperative [Member]
Related Party Transaction [Line Items]
Member distribution revenue	138.2	144.5	168.4
Delaware Electric Cooperative, Inc. [Member]
Related Party Transaction [Line Items]
Member distribution revenue	109.1	110.0	121.6
Choptank Electric Cooperative, Inc. [Member]
Related Party Transaction [Line Items]
Member distribution revenue	72.1	73.7	83.1
Southside Electric Cooperative [Member]
Related Party Transaction [Line Items]
Member distribution revenue	51.8	56.9	69.8
A&N Electric Cooperative [Member]
Related Party Transaction [Line Items]
Member distribution revenue	44.0	48.0	54.7
Mecklenburg Electric Cooperative [Member]
Related Party Transaction [Line Items]
Member distribution revenue	32.6	36.8	45.1
Prince George Electric Cooperative [Member]
Related Party Transaction [Line Items]
Member distribution revenue	20.2	22.9	26.9
Northern Neck Electric Cooperative [Member]
Related Party Transaction [Line Items]
Member distribution revenue	16.9	20.2	24.1
Community Electric Cooperative [Member]
Related Party Transaction [Line Items]
Member distribution revenue	10.5	11.0	14.1
BARC Electric Cooperative [Member]
Related Party Transaction [Line Items]
Member distribution revenue	$ 8.2	$ 9.2	$ 11.0