Short-Term Debt and Credit Agreements (Commercial Paper, Bank Loans and Letters of Credit Outstanding) (Detail) - USD ($)		Dec. 31, 2020	[1]	Dec. 31, 2019
Line Of Credit Facility [Line Items]
Facility Limit	[2]	$ 6,000,000,000		$ 6,000,000,000
Outstanding Commercial Paper	[2],[3]	627,000,000		836,000,000
Outstanding Letters of Credit	[2]	100,000,000		89,000,000
Facility Capacity Available	[2]	5,273,000,000		5,075,000,000
Virginia Electric and Power Company
Line Of Credit Facility [Line Items]
Facility Limit	[4]	6,000,000,000		6,000,000,000
Outstanding Commercial Paper	[4],[5]	45,000,000		243,000,000
Outstanding Letters of Credit	[4]	$ 12,000,000		$ 7,000,000

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

[2] 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.

[3] The weighted-average interest rates of the outstanding commercial paper supported by Dominion Energy’s credit facility was 0.29% and 2.10% at December 31, 2020 and 2019, respectively.

[4] The full amount of the facility is available to Virginia Power, less any amounts outstanding to co-borrowers Dominion Energy, 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, 2020, 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.

[5] The weighted-average interest rates of the outstanding commercial paper supported by the credit facility was 0.30% and 2.10% at December 31, 2020 and 2019, respectively.