Operating Segments - Virginia Power (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Gain (loss) on investments	$ (113)	$ 152
Operating Segments
Segment Reporting Information [Line Items]
After- tax net benefits (expenses)	(269)	(87)
Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain (loss) on investments	(125)	134
Gain (loss) on investments, after tax	(102)	100
Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
After- tax net benefits (expenses)	(311)	71
After- tax net benefits (expenses) for specific items	(289)	115
Operating Segments | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
After- tax net benefits (expenses)	(159)
Charge associated with storm damage and service restoration	94	51
Charge associated with storm damage and service restoration, after tax	70	38
Charge for amortization of a regulatory asset, 2021 Triennial Review	61
Charge for amortization of a regulatory asset, 2021 Triennial Review, after tax	45
Benefit for change in CCRO reserve		130
Benefit for change in CCRO reserve, after tax		97
Charges associated with budget process related to customer arrears		76
Charges associated with budget process related to customer arrears, after tax		56
Loss from unbilled revenue reduction		151
Loss from unbilled revenue reduction, after tax		112
Operating Segments | Virginia Electric and Power Company | Corporate and Other
Segment Reporting Information [Line Items]
After- tax net benefits (expenses)	(159)	(58)
After- tax net benefits (expenses) for specific items	$ (130)	$ (117)