Significant Accounting Policies (Reconciliation of Total Cash, Restricted Cash and Equivalents) (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023		Sep. 30, 2023	Dec. 31, 2022
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	$ 1,776	$ 184	[1]
Restricted cash and equivalents		$ 4		$ 4	$ 2
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
VIE
Cash Cash Equivalents And Restricted Cash [Line Items]
Restricted cash and equivalents	$ 100
Current Assets Held for Sale
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents		$ 33		$ 39	$ 34

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2023 has been derived from the audited Consolidated Balance Sheet at that date.