Significant Accounting Policies (Reconciliation of Total Cash, Restricted Cash and Equivalents (Detail) - USD ($) $ in Millions		Jun. 30, 2019	Dec. 31, 2018		Jun. 30, 2018	Dec. 31, 2017
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents		$ 382	$ 268	[1]	$ 190	$ 120
Restricted cash and equivalents	[2]	178	123		164	65
Cash, restricted cash and equivalents shown in the Consolidated Statements of Cash Flows		560	391		354	185
Virginia Electric and Power Company
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents		17	29	[3]	20	14
Restricted cash and equivalents	[2]	8	9		10	10
Cash, restricted cash and equivalents shown in the Consolidated Statements of Cash Flows		25	38		30	24
Dominion Energy Gas Holdings, LLC
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents		13	10	[4]	5	4
Restricted cash and equivalents	[2]	8	24		24	26
Cash, restricted cash and equivalents shown in the Consolidated Statements of Cash Flows		$ 21	$ 34		$ 29	$ 30

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2018 has been derived from the audited Consolidated Balance Sheet at that date.

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

[3] Virginia Power’s Consolidated Balance Sheet at December 31, 2018 has been derived from the audited Consolidated Balance Sheet at that date.

[4] Dominion Energy Gas’ Consolidated Balance Sheet at December 31, 2018 has been derived from the audited Consolidated Balance Sheet at that date.