Significant Accounting Policies (Reconciliation of Total Cash, Restricted Cash and Equivalents) (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022		Sep. 30, 2022	Dec. 31, 2021
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	$ 137	$ 120	[1]
Restricted cash and equivalents	$ 4	$ 2		$ 2	$ 1
Restricted Cash and Cash Equivalents, Current, Statement of Financial Position [Extensible Enumeration]	Current assets held for sale	Current assets held for sale		Current assets held for sale	Current assets held for sale
Current Assets Held for Sale
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	$ 39	$ 34		$ 25	$ 34

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2022 has been derived from the audited Consolidated Balance Sheet at that date and recast for certain events as discussed in Note 1.