Operating Segments - Dominion Energy (Narrative) (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Gain (loss) on investments	$ 370	$ 101
Operating Segments
Segment Reporting Information [Line Items]
After- tax net benefits (expenses)	(617)	(1,300)
Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain (loss) on investments	309
Gain (loss) on investments, after tax	248
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
After- tax net benefits (expenses)	(642)	(3,600)
After- tax net benefits (expenses) for specific items	(492)	(3,400)
Contracted Assets | Operating Segments
Segment Reporting Information [Line Items]
Loss related to economic hedging activities	447
Loss related to economic hedging activities, after tax	336
Charge associated with revision in estimated recovery of spent nuclear fuel costs associated with the decommissioning of Kewaunee	44
Charge associated with revision in estimated recovery of spent nuclear fuel costs associated with the decommissioning of Kewaunee, after tax	35
Charge associated with certain nonregulated solar generation facilities		405
Charge associated with certain nonregulated solar generation facilities, after tax		298
Contracted Assets | Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain (loss) on investments, after tax	218
Contracted Assets | Operating Segments | Fowler Ridge
Segment Reporting Information [Line Items]
Charge associated with the sale of assets		221
Charge associated with the sale of assets, after tax		171
Dominion Energy Virginia | Operating Segments
Segment Reporting Information [Line Items]
Benefit for change in expected CCRO reserve	130
Benefit for change in expected 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
Charge associated with storm damage and service restoration	68
Charge associated with storm damage and service restoration, after tax	50
Loss from unbilled revenue reduction	151
Loss from unbilled revenue reduction, after tax	112
Net charge associated with proposed settlement of the 2021 Triennial Review	119
Net charge associated with proposed settlement of the 2021 Triennial Review, after tax	89
Charge for expected CCRO		200
Charge for expected CCRO, after tax		149
Dominion Energy Virginia | Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain (loss) on investments, after tax	30
Dominion Energy Virginia | Operating Segments | Electric Generation Facilities
Segment Reporting Information [Line Items]
Asset early retirement expense		751
Asset early retirement expense after tax		$ 564
Dominion Energy South Carolina Inc | Operating Segments
Segment Reporting Information [Line Items]
Litigation settlement expense	70
Litigation settlement expense, after tax	53
Dominion Energy South Carolina Inc | Operating Segments | South Carolina Electric Base Rate Case
Segment Reporting Information [Line Items]
Charges associated with settlement	266
Charges associated with settlement, after tax	$ 199