Operating Segments - Dominion Energy (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Gain loss on investments	$ 152	$ (526)
Operating Segments
Segment Reporting Information [Line Items]
After-tax net income (expense)	(87)	(1,000)
Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain loss on investments	134	(538)
Gain loss on investments, net of tax	100	(410)
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
After-tax net income (expense)	71	(1,100)
After- tax net income (expense) for specific items	115	(1,100)
Dominion Energy Virginia | Operating Segments
Segment Reporting Information [Line Items]
Benefit for change in CCRO reserve	130
Benefit for change in CCRO reserve, net of tax	97
Charges associated with budget process related to customer arrears	76
Charges associated with budget process related to customer arrears, net of tax	56
Charge associated with storm damage and service restoration	51
Charge associated with storm damage and service restoration, after tax	38
Loss from unbilled revenue reduction	151
Loss from unbilled revenue reduction, net of tax	112
Dominion Energy Virginia | Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain loss on investments, net of tax	12	(46)
Dominion Energy Virginia | Operating Segments | Electric Generation Facilities
Segment Reporting Information [Line Items]
Asset early retirement expense		754
Asset early retirement expense after tax		566
Dominion Energy South Carolina Inc | Operating Segments
Segment Reporting Information [Line Items]
Litigation settlement expense	60
Litigation settlement expense, after tax	45
Contracted Assets | Operating Segments | Nuclear Decommissioning Trust Funds
Segment Reporting Information [Line Items]
Gain loss on investments, net of tax	$ 88	$ (364)