Operating Segments - Virginia Power (Narrative) (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Gain (loss) on investments	$ (556)	$ 364
Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Gain (loss) on investments	(75)	43
Operating Segments
Segment Reporting Information [Line Items]
After- tax net benefits (expenses)	(1,500)	(314)
Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain (loss) on investments	(579)	328
Gain (loss) on investments, after tax	(450)	256
Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
After- tax net benefits (expenses)	(1,500)	(358)
After- tax net benefits (expenses) for specific items	(1,400)	(228)
Operating Segments | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
After- tax net benefits (expenses)	(554)
Charge in connection with proposed comprehensive settlement agreement for fuel expenses	191
Charge in connection with proposed comprehensive settlement agreement for fuel expenses, after-tax	142
Charge for RGGI compliance cost	180
Charge for RGGI compliance cost, after tax	134
Charge associated with storm damage and service restoration	94	68
Charge associated with storm damage and service restoration, after tax	70	50
Charges for Dismantling cost	42
Charges for Dismantling cost, after tax	31
Charge for amortization of a regulatory asset, 2021 Triennial Review	122
Charge for amortization of a regulatory asset, 2021 Triennial Review, after tax	91
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		77
Charges associated with budget process related to customer arrears, after tax		57
Loss from unbilled revenue reduction		151
Loss from unbilled revenue reduction, after tax		112
Operating Segments | Virginia Electric and Power Company | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain (loss) on investments	78
Gain (loss) on investments, after tax	58
Operating Segments | Virginia Electric and Power Company | Corporate and Other
Segment Reporting Information [Line Items]
After- tax net benefits (expenses)	(554)	(73)
After- tax net benefits (expenses) for specific items	(547)	$ (94)
After-tax net benefits (expenses) attributable to operating segment	$ (527)