Acquisitions and Dispositions (Acquisition of SCANA) (Narrative) (Detail) - USD ($) shares in Millions, $ in Millions		1 Months Ended	2 Months Ended	3 Months Ended	12 Months Ended
		Jan. 31, 2019	Oct. 31, 2017	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition And Dispositions [Line Items]
Stock issued during period for acquisition, value						$ 6,818
Regulatory Liabilities					$ 10,996	10,659
Regulatory liabilities-current					809	$ 455
SCANA
Business Acquisition And Dispositions [Line Items]
Stock issued during period for acquisition, shares		95.6				95.6
Stock issued during period for acquisition, value		$ 6,800				$ 6,800
Common stock agreed to be issued, percentage		0.669%
Total outstanding debt		$ 6,900				6,707
Business combination, refund to customers		$ 2,000
Period to provide refund to customer		20 years	20 years
Regulatory Liabilities			$ 1,100
Regulatory liabilities-current			67
Refund Liability to electric service customers			1,000
Remaining regulatory asset	[1]					3,940
Other Commitment, Fiscal Year Maturity [Abstract]
Charitable contributions, annual committed increase for next five years					$ 1
SCANA | Minimum
Other Commitment, Fiscal Year Maturity [Abstract]
Charitable contributions, period committed for annual increase		5 years
SCANA | NND Project
Business Acquisition And Dispositions [Line Items]
Period to provide refund to customer		20 years
Business combination cost related to exclusion from rate recovery		$ 2,400
Remaining regulatory asset		2,800
Remaining regulatory asset current		138
SCANA | Dominion Energy South Carolina Inc
Business Acquisition And Dispositions [Line Items]
Period to provide refund to customer				11 years
Charge for refund of amounts from customers				$ 1,000
Charge for refund of amounts from customers, current				$ 137
After tax charge in statements of income						$ 756
SCANA | Toshiba Corporation
Business Acquisition And Dispositions [Line Items]
Cash consideration			$ 1,100
SCANA | Columbia Energy
Business Acquisition And Dispositions [Line Items]
Business combination cost related to exclusion from rate recovery		$ 180

[1] Includes $258 million of certain income tax-related regulatory assets associated with the NND Project for which Dominion Energy committed to forgo recovery in accordance with the SCANA Merger Approval Order. See Note 5 for additional information.