Commitments and Contingencies (Nuclear Operations) (Narrative) (Detail) - USD ($)	1 Months Ended					3 Months Ended	12 Months Ended
	Feb. 28, 2022	Jun. 30, 2021	May 31, 2021	Feb. 28, 2021	Mar. 31, 2015	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Minimum financial assurance							$ 3,200,000,000
NRC minimum requirement for nuclear power plant licensees							1,060,000,000.00
Maximum assessment for premiums on insurance policy							33,000,000
Maximum assessment for insurance policy							76,000,000
Spent Nuclear Fuel
Loss Contingencies [Line Items]
Receivables							52,000,000	$ 46,000,000
Forecast
Loss Contingencies [Line Items]
Settlement amount awarded from other party	$ 48,000,000
Maximum
Loss Contingencies [Line Items]
Amount that could be assessed for each licensed reactor							138,000,000
Amount that could be assessed for each licensed reactor per reactor							21,000,000
Millstone, Summer, Surry and North Anna
Loss Contingencies [Line Items]
Amount of coverage purchased from commercial insurance pools							450,000,000
Kewaunee
Loss Contingencies [Line Items]
Maximum assessment for premiums on insurance policy					$ 50,000,000
Surry and North Anna
Loss Contingencies [Line Items]
Settlement amount awarded from other party							25,000,000	24,000,000	$ 15,000,000
Millstone
Loss Contingencies [Line Items]
Settlement amount awarded from other party							9,000,000	11,000,000	11,000,000
Summer
Loss Contingencies [Line Items]
Settlement amount awarded from other party							1,000,000	4,000,000	$ 3,000,000
Nuclear Obligations
Loss Contingencies [Line Items]
Maximum liability protection per nuclear incident amount							13,500,000,000
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	$ 13,800,000,000		$ 13,700,000,000
Nuclear Obligations | Kewaunee
Loss Contingencies [Line Items]
Maximum liability protection per nuclear incident amount							100,000,000
Virginia Electric and Power Company
Loss Contingencies [Line Items]
Minimum financial assurance							1,900,000,000
Maximum assessment for premiums on insurance policy							35,000,000
Maximum assessment for insurance policy							9,000,000
Virginia Electric and Power Company | Spent Nuclear Fuel
Loss Contingencies [Line Items]
Receivables							39,000,000	$ 35,000,000
DESC | Non-nuclear Obligation | European Mutual Association
Loss Contingencies [Line Items]
Property insurance coverage							415,000,000
Annual Premium							$ 2,000,000