Investments (Narrative) (Detail)		1 Months Ended			3 Months Ended			6 Months Ended		12 Months Ended
		Jul. 31, 2020 USD ($)	Oct. 31, 2017 USD ($)	Sep. 30, 2014 mi	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investees					$ (2,281,000,000)	$ 39,000,000		$ (2,228,000,000)	$ 80,000,000
Distributions received from investment								46,000,000	57,000,000
Carrying amount of investment that exceeded share of underlying equity					96,000,000	110,000,000		96,000,000	110,000,000
Equity method investment goodwill					175,000,000	159,000,000		175,000,000	159,000,000
Cost to acquire equity method investments											$ 184,000,000
Maximum obligation amount under credit facility	[1]				6,000,000,000			6,000,000,000
Guarantee liability	[2]				5,248,000,000			5,248,000,000
Cumulative-effect of changes in accounting principles								(48,000,000)
Contributions to equity method affiliates								178,000,000	0
Other payables	[3]				2,446,000,000			2,446,000,000				$ 1,827,000,000	[4]
Investment in equity method affiliates					584,000,000			584,000,000				1,646,000,000	[4]
Revenue					3,470,000,000	3,746,000,000		7,793,000,000	7,376,000,000
Other receivables	[3]				233,000,000			233,000,000				367,000,000	[4]
Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investees					8,000,000	9,000,000		23,000,000	22,000,000
Maximum obligation amount under credit facility	[5]				1,500,000,000			1,500,000,000
Other payables	[6]				382,000,000			382,000,000				289,000,000	[7]
Investment in equity method affiliates					310,000,000			310,000,000				312,000,000	[7]
Revenue					509,000,000	529,000,000		1,064,000,000	1,094,000,000
Other receivables	[6]				12,000,000			12,000,000				26,000,000	[7]
Dominion Energy Gas Holdings, LLC | Partnership Interest
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investees								23,000,000	22,000,000
Distributions received from investment								25,000,000	30,000,000
Carrying amount of investment that exceeded share of underlying equity					146,000,000			146,000,000				146,000,000
Investment in equity method affiliates					310,000,000			310,000,000				312,000,000
Pivotal LNG | Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage acquired											100.00%
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity method investees					(2,300,000,000)	29,000,000		(2,300,000,000)	53,000,000
Net income (losses) from abandonment of project					(4,400,000,000)	61,000,000		(4,300,000,000)	114,000,000
Contributions to equity method affiliates					13,000,000	33,000,000		29,000,000	128,000,000
Atlantic Coast Pipeline | Financial Guarantee
Schedule of Equity Method Investments [Line Items]
Guarantee liability												14,000,000
Atlantic Coast Pipeline | Revolving Credit Facility
Schedule of Equity Method Investments [Line Items]
Maximum obligation amount under credit facility			$ 3,400,000,000
Credit facility, maturity date			Oct. 31, 2021
Credit facility, amount borrowed					1,800,000,000			1,800,000,000
Atlantic Coast Pipeline | Revolving Credit Facility | Financial Guarantee
Schedule of Equity Method Investments [Line Items]
Cumulative-effect of changes in accounting principles								(48,000,000)
Atlantic Coast Pipeline | Subsequent Event | Revolving Credit Facility
Schedule of Equity Method Investments [Line Items]
Maximum obligation amount under credit facility		$ 1,900,000,000
Atlantic Coast Pipeline | Other Current Liabilities
Schedule of Equity Method Investments [Line Items]
Liabilities from abandonment of project					1,000,000.0			1,000,000.0
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 payables					5,000,000			5,000,000				7,000,000
Revenue					17,000,000	$ 26,000,000		37,000,000	$ 57,000,000
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
JAX LNG LLC | Pivotal LNG
Schedule of Equity Method Investments [Line Items]
Percentage of interest held											50.00%
Blue Racer
Schedule of Equity Method Investments [Line Items]
Additional consideration including interest received in connection with sale							$ 151,000,000
Ownership interest percentage of limited partner interests										50.00%
Fowler Ridge | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Percentage of interest held		50.00%
Net payment of long-term power and capacity contract		$ 150,000,000
Contract termination loss		220,000,000
Contract termination loss net of tax		$ 170,000,000
Finite Lived Equity Method Investment Basis Difference
Schedule of Equity Method Investments [Line Items]
Equity method investment goodwill					79,000,000			79,000,000				49,000,000
Trading Securities
Schedule of Equity Method Investments [Line Items]
Rabbi trust securities					$ 121,000,000			$ 121,000,000				$ 120,000,000

[1] 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.

[2] Excludes Dominion Energy's guarantees for the new corporate office properties discussed in Note 15 to the Consolidated Financial Statements in the Companies’ Annual Report on Form 10-K for the year ended December 31, 2019 and in Note 14 in this report.

[3] See Note 10 for amounts attributable to related parties.

[4] Dominion Energy’s Consolidated Balance Sheet at December 31, 2019 has been derived from the audited Consolidated Balance Sheet at that date.

[5] A maximum of $1.5 billion of the facility is available to Dominion Energy Gas, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power, Questar Gas and DESC. The sub-limit for Dominion Energy Gas is set within the facility limit but can be changed at the option of the borrowers under the credit facility multiple times per year. At June 30, 2020, the sub-limit for Dominion Energy Gas was $750 million. If Dominion Energy Gas has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. This credit facility matures in March 2023 and can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.5 billion (or the sub-limit, whichever is less) of letters of credit.

[6] See Note 19 for amounts attributable to related parties.

[7] Dominion Energy Gas’ Consolidated Balance Sheet at December 31, 2019 has been derived from the audited Consolidated Balance Sheet at that date.