Significant Accounting Policies (Reconciliation of Total Cash, Restricted Cash and Equivalents) (Detail) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	[1]	$ 179	$ 166	$ 268	$ 120
Cash and cash equivalents		172	135
Restricted cash and equivalents	[2],[3]	68	103	123	65
Cash, restricted cash and equivalents shown in the Consolidated Statements of Cash Flows		247	269	391	185
Virginia Electric and Power Company
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents		35	17	29	14
Restricted cash and equivalents	[3]		7	9	10
Cash, restricted cash and equivalents shown in the Consolidated Statements of Cash Flows		$ 35	$ 24	$ 38	$ 24

[1] At December 31, 2020, December 31, 2019, December 31, 2018 and December 31, 2017, Dominion Energy had $7 million, $31 million, $110 million and $21 million of cash and cash equivalents included in current assets held for sale, respectively.

[2] At December 31, 2020, December 31, 2019, December 31, 2018 and December 31, 2017, Dominion Energy had $3 million, $12 million, $89 million and $39 million of restricted cash 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.