Commitments and Contingencies (Nuclear Insurance) (Detail) $ in Millions	Dec. 31, 2021 USD ($)
Millstone
Guarantee Obligations [Line Items]
Property insurance coverage	$ 1,060
Kewaunee
Guarantee Obligations [Line Items]
Property insurance coverage	50
Summer
Guarantee Obligations [Line Items]
Property insurance coverage	2,750
Surry | Virginia Electric and Power Company
Guarantee Obligations [Line Items]
Property insurance coverage	1,060
North Anna | Virginia Electric and Power Company
Guarantee Obligations [Line Items]
Property insurance coverage	$ 1,060