Investments (Narrative) (Detail)			1 Months Ended							2 Months Ended		3 Months Ended									12 Months Ended
		Nov. 30, 2020 USD ($)	Nov. 30, 2020	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Oct. 31, 2019	Sep. 30, 2018 USD ($)	Oct. 31, 2017 USD ($)	Sep. 30, 2014 mi	Dec. 31, 2020 USD ($)		Dec. 31, 2020 USD ($)		Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)		Dec. 31, 2019 USD ($)		Dec. 31, 2018 USD ($)		Jul. 31, 2020 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity in earnings(losses) on investments																					$ 40,000,000		$ 8,000,000		$ 76,000,000
Net income (loss) from discontinued operations including noncontrolling interest												$ (125,000,000)		$ 19,000,000	$ (2,001,000,000)	$ 229,000,000	$ 190,000,000	$ 38,000,000	$ 257,000,000	$ 231,000,000	(1,878,000,000)	[1],[2]	716,000,000	[1],[2]	452,000,000	[1],[2]
Distributions received from investment																					102,000,000		38,000,000		111,000,000
Carrying amount of investment that exceeded share of underlying equity					$ (35,000,000)					$ 213,000,000		213,000,000					(35,000,000)				213,000,000		(35,000,000)
Equity method investment goodwill					11,000,000					27,000,000		27,000,000					11,000,000				27,000,000		11,000,000
Income before income taxes																					1,411,000,000		869,000,000		2,619,000,000
Contributions to equity method affiliates																					148,000,000		209,000,000		428,000,000
Current liabilities held for sale					1,039,000,000					625,000,000		625,000,000					1,039,000,000				625,000,000		1,039,000,000
Debt maximum borrowing capacity	[3]				6,000,000,000					6,000,000,000	[4]	6,000,000,000	[4]				6,000,000,000				6,000,000,000	[4]	6,000,000,000
Guarantee liability	[5]									3,527,000,000		3,527,000,000									3,527,000,000
Retained earnings					7,576,000,000					4,189,000,000		4,189,000,000					7,576,000,000				4,189,000,000		7,576,000,000
Other	[6]				2,132,000,000					1,725,000,000		1,725,000,000					2,132,000,000				1,725,000,000		2,132,000,000
Operating revenue from contracts with customers																					13,752,000,000		13,745,000,000		10,891,000,000
Other receivables					340,000,000					212,000,000		212,000,000					340,000,000				212,000,000		340,000,000
Income tax expense		$ 336,000,000																			83,000,000		209,000,000		522,000,000
Current assets	[7]				535,000,000					1,482,000,000		1,482,000,000					535,000,000				1,482,000,000		535,000,000
Assets					6,096,000,000					6,886,000,000		6,886,000,000					6,096,000,000				6,886,000,000		6,096,000,000
Liabilities					$ 9,940,000,000					10,843,000,000		10,843,000,000					$ 9,940,000,000				10,843,000,000		$ 9,940,000,000
Retail Energy Marketing Operations
Schedule of Equity Method Investments [Line Items]
Assets										63,000,000		63,000,000									63,000,000
Liabilities										15,000,000		$ 15,000,000									15,000,000
Cove Point
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage of limited partner interests					25.00%	25.00%
Ownership percentage			100.00%
Cove Point
Schedule of Equity Method Investments [Line Items]
Distributions received from investment										70,000,000
Ownership interest percentage of limited partner interests																							25.00%
Ownership percentage		50.00%	50.00%
Contributions to equity method affiliates										$ 0
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Equity in earnings(losses) on investments																					(2,300,000,000)		$ 117,000,000		67,000,000
Contributions to equity method affiliates																					$ 107,000,000		$ 186,000,000		414,000,000
Cost to acquire equity method investments																$ 184,000,000
Percentage ownership in total units					48.00%					53.00%		53.00%					48.00%				53.00%		48.00%
Equity in earnings (losses) on investments after tax																					$ (1,800,000,000)		$ 118,000,000		67,000,000
Current liabilities held for sale										$ 1,100,000,000		$ 1,100,000,000									1,100,000,000
Atlantic Coast Pipeline | Financial Guarantee
Schedule of Equity Method Investments [Line Items]
Guarantee liability					$ 14,000,000					6,000,000		6,000,000					$ 14,000,000				6,000,000		14,000,000
Atlantic Coast Pipeline | Revolving Credit Facility
Schedule of Equity Method Investments [Line Items]
Debt maximum borrowing capacity								$ 3,400,000,000																			$ 1,900,000,000
Credit facility, maturity date								Oct. 31, 2021
Credit facility, amount borrowed										1,800,000,000		1,800,000,000									1,800,000,000
Atlantic Coast Pipeline | Revolving Credit Facility | Financial Guarantee | Cumulative-effect of Changes in Accounting Principles
Schedule of Equity Method Investments [Line Items]
Retained earnings										48,000,000		48,000,000									48,000,000
Atlantic Coast Pipeline | Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage acquired																5.00%
Percentage ownership in total units																53.00%
Atlantic Coast Pipeline | DETI
Schedule of Equity Method Investments [Line Items]
Other					7,000,000												7,000,000						7,000,000
Operating revenue from contracts with customers																					49,000,000		103,000,000		$ 203,000,000
Other receivables					7,000,000												7,000,000						$ 7,000,000
Atlantic Coast Pipeline | Pipelines | Jointly Owned Natural Gas Pipeline | Distribution
Schedule of Equity Method Investments [Line Items]
Length of natural gas pipeline (in miles) | mi									600
Duration of contract									20 years
Blue Racer
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage of limited partner interests																									50.00%
Additional consideration including interest received in connection with sale																				$ 151,000,000
Fowler Ridge
Schedule of Equity Method Investments [Line Items]
Percentage of equity interest sold to noncontrolling interest owners				50.00%										50.00%
Net payment of long-term power and capacity contract				$ 150,000,000
Contract termination loss																					221,000,000
Contract termination loss net of tax																					$ 165,000,000
Wrangler Retail Gas Holdings LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage of limited partner interests																					20.00%		20.00%
Amount of gain from sale																					$ 64,000,000		$ 147,000,000
Limited partnership interest sale transaction, proceeds received																					74,000,000		301,000,000
Initial fair value					75,000,000					13,000,000		13,000,000					75,000,000				13,000,000		75,000,000
Goodwill write-off																							73,000,000
Income tax expense																					19,000,000		82,000,000
Current assets					41,000,000												41,000,000						41,000,000
Catalyst Old River Hydroelectric Limited Partnership
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage of limited partner interests							25.00%
Finite Lived Equity Method Investment Basis Difference
Schedule of Equity Method Investments [Line Items]
Equity method investment goodwill					$ (46,000,000)					$ (41,000,000)		$ (41,000,000)					(46,000,000)				(41,000,000)		(46,000,000)
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Net income (loss) from discontinued operations including noncontrolling interest																					$ (2,300,000,000)		117,000,000		$ 67,000,000
Ownership percentage	[8]									53.00%		53.00%									53.00%
Cove Point
Schedule of Equity Method Investments [Line Items]
Ownership percentage	[9]									50.00%		50.00%									50.00%
Cove Point | Cove Point
Schedule of Equity Method Investments [Line Items]
Equity in earnings(losses) on investments																					$ 40,000,000
Distributions received from investment																									50,000,000
Ownership interest percentage of limited partner interests			25.00%		25.00%
Ownership percentage		50.00%	50.00%
Income before income taxes																					511,000,000		471,000,000		292,000,000
Cove Point | Finite Lived Equity Method Investment Basis Difference
Schedule of Equity Method Investments [Line Items]
Equity method investment goodwill										$ 227,000,000		$ 227,000,000									227,000,000
Pivotal LNG | Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage acquired																100.00%
Pivotal LNG | JAX LNG LLC
Schedule of Equity Method Investments [Line Items]
Percentage of equity interest sold to noncontrolling interest owners																50.00%
Blue Racer
Schedule of Equity Method Investments [Line Items]
Amount of gain from sale																									546,000,000
Amount of after tax gain from sale																									390,000,000
Up-front cash consideration																									1,050,000,000.00
Additional deferred consideration, subject to increase for interest cost effective payable upon purchaser's availability of cash																									150,000,000
Aggregate amount of contingent consideration, maximum																									$ 300,000,000
Catalyst Old River Hydroelectric Limited Partnership
Schedule of Equity Method Investments [Line Items]
Limited partnership interest sale transaction, proceeds received							$ 91,000,000
Catalyst Old River Hydroelectric Limited Partnership | Other Income
Schedule of Equity Method Investments [Line Items]
Amount of gain from sale							87,000,000
Amount of after tax gain from sale							$ 63,000,000
Trading Securities
Schedule of Equity Method Investments [Line Items]
Rabbi trust securities					$ 120,000,000					$ 134,000,000		$ 134,000,000					$ 120,000,000				$ 134,000,000		$ 120,000,000

[1] Includes income tax expense (benefit) of $(204) million, $142 million and $58 million for the years ended December 31, 2020, 2019 and 2018, respectively

[2] See Note 9 for amounts attributable to related parties

[3] This credit facility matures in March 2023 and can be used by the borrowers under the credit facility to support bank borrowings and the issuance of commercial paper, as well as to support up to a combined $2.0 billion of letters of credit.

[4] In October 2020, the joint revolving credit facility was amended to remove Dominion Energy Gas as a co-borrower.

[5] Excludes Dominion Energy’s guarantees for the new corporate office properties and an offshore wind installation vessel discussed in Note 15.

[6] See Note 9 for amounts attributable to related parties.

[7] See Note 9 for amounts attributable to related parties.

[8] Dominion Energy owned 53% and 48% of Atlantic Coast Pipeline at December 31, 2020 and 2019, respectively. See discussion below for additional information.

[9] Effective November 2020, following the completion of the GT&S Transaction, Dominion Energy began accounting for its 50% noncontrolling interest in Cove Point as an equity method investment.  See discussion below and Note 3 for additional information.