Significant Accounting Policies (Reconciliation of Total Cash, Restricted Cash and Equivalents) (Parenthetical) (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021		Mar. 31, 2021	Dec. 31, 2020
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	$ 444	$ 283	[1]
Current Assets Held for Sale
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	2	0		$ 14	$ 7
Restricted cash and equivalents	$ 0	$ 0		$ 3	$ 3

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2021 has been derived from the audited Consolidated Balance Sheet at that date.