Operating Segments - Dominion Energy (Narrative) (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Gain (loss) on investments	$ 364	$ (117)
Operating Segments
Segment Reporting Information [Line Items]
After-tax net expense	(314)	(780)
Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain (loss) on investments	328	(145)
Gain (loss) on investments, after tax	256	(115)
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
After-tax net expense	358	(3,000)
After- tax net expense for specific items	228	(2,900)
Dominion Energy Virginia | Operating Segments
Segment Reporting Information [Line Items]
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
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
Dominion Energy Virginia | Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain (loss) on investments, after tax	30	(15)
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
Contracted Assets | Operating Segments
Segment Reporting Information [Line Items]
Loss related to economic hedging activities	169
Loss related to economic hedging activities, after tax	127
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
Contracted Assets | Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain (loss) on investments, after tax	$ 226	$ (100)