Commitments and Contingencies (Guarantees, Surety Bonds and Letters of Credit) (Detail) - USD ($)		1 Months Ended
		Feb. 29, 2020	Oct. 31, 2017	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Guarantor Obligations [Line Items]
Debt maximum borrowing capacity	[1]			$ 6,000,000,000		$ 6,000,000,000
Maximum Exposure				5,151,000,000
Revolving Credit Facility
Guarantor Obligations [Line Items]
Debt maximum borrowing capacity					$ 700,000,000
Cove Point
Guarantor Obligations [Line Items]
Maximum Exposure				1,900,000,000
Virginia Electric and Power Company
Guarantor Obligations [Line Items]
Debt maximum borrowing capacity	[2]			6,000,000,000		6,000,000,000
Dominion Energy Gas Holdings, LLC
Guarantor Obligations [Line Items]
Debt maximum borrowing capacity	[3]			1,500,000,000		1,500,000,000
Nuclear Obligations
Guarantor Obligations [Line Items]
Maximum Exposure				182,000,000
Commodity Transactions
Guarantor Obligations [Line Items]
Maximum Exposure				2,215,000,000
Financial Guarantee [Member] | Revolving Credit Facility | Atlantic Coast Pipeline
Guarantor Obligations [Line Items]
Debt maximum borrowing capacity			$ 3,400,000,000
Financial Guarantee [Member] | Equity Method Investee [Member]
Guarantor Obligations [Line Items]
Maximum potential loss exposure, limited guarantee percentage			48.00%
Guarantee liability				14,000,000		$ 21,000,000
Guarantee recorded amount				1,800,000,000
Maximum Exposure				27,000,000
Solar
Guarantor Obligations [Line Items]
Maximum Exposure				477,000,000
Other
Guarantor Obligations [Line Items]
Maximum Exposure				377,000,000
Surety Bond [Member]
Guarantor Obligations [Line Items]
Maximum Exposure				163,000,000
Surety Bond [Member] | Virginia Electric and Power Company
Guarantor Obligations [Line Items]
Maximum Exposure				77,000,000
Surety Bond [Member] | Dominion Energy Gas Holdings, LLC
Guarantor Obligations [Line Items]
Maximum Exposure				26,000,000
Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Maximum Exposure				$ 89,000,000
Subsequent Event | Financial Guarantee [Member] | Equity Method Investee [Member] | Atlantic Coast Pipeline
Guarantor Obligations [Line Items]
Additional borrowing		$ 27,000,000

[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] The full amount of the facility is available to Virginia Power, less any amounts outstanding to co-borrowers Dominion Energy, Dominion Energy Gas, Questar Gas and DESC. The sub-limit for Virginia Power 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 December 31, 2019, the sub-limit for Virginia Power was $1.5 billion. If Virginia Power 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 $2.0 billion (or the sub-limit, whichever is less) of letters of credit.

[3] 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 December 31, 2019, 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.