Acquisitions and Dispositions (Schedule of Preliminary Allocation of Purchase Price to Assets Acquired and Liabilities Assumed) (Parenthetical) (Detail) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Jan. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Cash, restricted cash and equivalents			$ 247	$ 269	$ 391	$ 185
Impairment of assets and other charges			$ 2,105	1,520	$ 12
Intangible assets, estimated weighted-average amortization period			11 years
Pension and other postretirement benefit liability			$ 1,706	2,364
SCANA
Business Acquisition [Line Items]
Cash, restricted cash and equivalents				389
Restricted cash				115
Equity method investment				31
Property, plant and equipment	[1],[2]			$ 11,006
Intangible assets, estimated weighted-average amortization period				5 years
Repayment of letter of credit advances		$ 40
Repayments of Commercial Paper		$ 173
Pension and other postretirement benefit liability				$ 379
Stock based compensation awards estimated fair value				$ 21
SCANA | Minimum
Business Acquisition [Line Items]
Property, plant and equipment, estimated useful lives				5 years
SCANA | Maximum
Business Acquisition [Line Items]
Property, plant and equipment, estimated useful lives				78 years
SCANA | NND Project
Business Acquisition [Line Items]
Property, plant and equipment				$ 105
Impairment of assets and other charges				105
Impairment of assets and other charges, after tax				79
SCANA | Dominion Energy South Carolina Inc | NND Project
Business Acquisition [Line Items]
Income tax regulatory assets				$ 258

[1] Includes $105 million of certain property, plant and equipment associated with the NND Project for which Dominion Energy committed to forgo recovery in accordance with the SCANA Merger Approval Order. As a result, Dominion Energy’s Consolidated Statements of Income for the year ended December 31, 2019 include a charge of $105 million ($79 million after-tax), included in impairment of assets and other charges (reflected in the Corporate and Other segment).

[2] Nonregulated property, plant and equipment, excluding land, will be depreciated on a straight-line basis over the remaining useful lives of such property, primarily ranging from 5 to 78 years.