Significant Accounting Policies (Reconciliation of Total Cash, Restricted Cash and Equivalents) (Detail) - USD ($) $ in Millions		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents		$ 166		$ 268	$ 120		$ 261
Restricted cash and equivalents	[1]	103		123	65		61
Cash, restricted cash and equivalents shown in the Consolidated Statements of Cash Flows		269		391	185		322
Virginia Electric and Power Company
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents		17		29	14		11
Restricted cash and equivalents	[1]	7		9	10
Cash, restricted cash and equivalents shown in the Consolidated Statements of Cash Flows		24		38	24		11
Dominion Energy Gas Holdings, LLC
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents		27	[2]	99	18	[2]	76	[2]
Restricted cash and equivalents	[1]	12		90	39		45
Cash, restricted cash and equivalents shown in the Consolidated Statements of Cash Flows		$ 39		$ 198	$ 57		$ 121

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

[2] At December 31, 2018, 2017 and 2016, Dominion Energy Gas had $9 million, $3 million and $14 million of cash and cash equivalents included in current assets of discontinued operations, respectively.