Long-Term and Short-Term Debt (Schedule of Line of Credit Facilities) (Detail) - Joint Revolving Credit Facility	Sep. 30, 2023 USD ($)	[1]
Debt Instrument [Line Items]
Maximum Facility Sub-Limit	$ 1,000,000,000
Outstanding Commercial Paper	287,000,000
Outstanding Letters of Credit	$ 0

[1] A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power and Questar Gas. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At September 30, 2023, the sub-limit for DESC was $500 million. If DESC 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 June 2026, with the potential to be extended by the borrowers to June 2028. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.0 billion (or the sub-limit, whichever is less) of letters of credit.