Commitments and Contingencies (Nuclear Insurance) (Narrative) (Detail) - USD ($)	1 Months Ended
	Jun. 30, 2021	May 31, 2021	Mar. 31, 2021	Feb. 28, 2021
Loss Contingencies [Line Items]
Maximum assessment for premiums on annual insurance policy	$ 76,000,000
Virginia Electric and Power Company
Loss Contingencies [Line Items]
Maximum assessment for premiums on annual insurance policy	35,000,000
Millstone
Loss Contingencies [Line Items]
Property insurance coverage		$ 1,700,000,000
NRC minimum requirement	1,060,000,000.00
North Anna
Loss Contingencies [Line Items]
Property insurance coverage		1,700,000,000
NRC minimum requirement	1,060,000,000.00
Surry
Loss Contingencies [Line Items]
Property insurance coverage		1,700,000,000
NRC minimum requirement	1,060,000,000.00
Nuclear Obligations | Secondary Financial Protection Program
Loss Contingencies [Line Items]
Maximum liability protection per nuclear incident amount	$ 13,500,000,000	$ 13,700,000,000	$ 13,700,000,000	$ 13,800,000,000