Quarterly Financial Data (Unaudited) (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended							12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2019
Parent Company Only Financial Information [Line Items]
Charges associated with legislation enacted related to customer arrears, net of tax	$ 94
Charge associated with certain nonregulated solar generation facilities, net of tax		$ 298
Charge associated with the sale of Fowler Ridge, net of tax		170
Charge for expected CCRO, net of tax		149
Virginia Electric and Power Company
Parent Company Only Financial Information [Line Items]
Charges associated with legislation enacted related to customer arrears, net of tax	$ 94
Charge for expected CCRO, net of tax		$ 149
After tax charge for charge for the planned early retirement							$ 409
After tax charge for closure costs							84
Gain loss on contract termination						$ 144
Voluntary retirement expenses after tax						100
Project abandonment costs after tax						47
SCANA
Parent Company Only Financial Information [Line Items]
Charge Related To Litigation Acquired After Tax					$ 244	75	134
Gain loss on investments held in nuclear decommissioning trust funds					$ 150
Charge related to a voluntary retirement program after tax						283
Charge related to a contract termination after tax.						$ 100
Merger and integration-related costs							1,300	$ 427
Charge For Refunds Collected From Customers							756
After tax charge for decommissioning costs							197
After tax charge for closure costs							84
SCANA | Dominion Energy Gas Holdings, LLC
Parent Company Only Financial Information [Line Items]
After tax charge for regulatory assets							277
SCANA | Virginia Electric and Power Company
Parent Company Only Financial Information [Line Items]
After tax charge for charge for the planned early retirement							$ 409
Electric Generation Facilities
Parent Company Only Financial Information [Line Items]
Asset early retirement expense after tax				$ 566
Electric Generation Facilities | Virginia Electric and Power Company
Parent Company Only Financial Information [Line Items]
Asset early retirement expense after tax				$ 561
Atlantic Coast Pipeline and Supple Header Project | Discontinued Operations, Disposed of by Means Other than Sale, Abandonment
Parent Company Only Financial Information [Line Items]
Charge associated with cancellation of investment, net of tax			$ 2,200