Significant Accounting Policies (Reconciliation of Total Cash, Restricted Cash and Equivalents) (Detail) - USD ($) $ in Millions		Jun. 30, 2021	Dec. 31, 2020		Jun. 30, 2020	Dec. 31, 2019
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	[1]	$ 259	$ 179		$ 675	$ 166
Restricted cash and equivalents	[2],[3]	45	68		67	103
Cash, restricted cash and equivalents shown in the Consolidated Statements of Cash Flows		304	247		742	269
Cash and cash equivalents		240	172	[4]
Virginia Electric and Power Company
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash, restricted cash and equivalents shown in the Consolidated Statements of Cash Flows		49	35		40	24
Cash and cash equivalents		49	35	[5]	37	17
Restricted cash and equivalents	[3]	$ 0	$ 0		$ 3	$ 7

[1] At June 30, 2021, June 30, 2020, December 31, 2020 and December 31, 2019, Dominion Energy had $19 million, $59 million, $7 million and $31 million of cash and cash equivalents included in current assets held for sale, respectively.

[2] At June 30, 2021, June 30, 2020, December 31, 2020 and December 31, 2019, Dominion Energy had $3 million, $12 million, $3 million and $12 million of restricted cash and equivalents included in current assets held for sale, respectively

[3] Restricted cash and equivalent balances are presented within other current assets in the Companies’ Consolidated Balance Sheets.

[4] Dominion Energy’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.

[5] Virginia Power’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.