Operating Revenue (Schedule of Operating Revenue) (Parenthetical) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers		$ 3,631	$ 3,324
Other revenues	[1]	227	142
NGL Midstream
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers		51	30
Renewable Energy Investment Tax Credits
Public Utilities General Disclosures [Line Items]
Other revenues		14
Dominion Energy Gas Holdings, LLC
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers		511	528
Other revenues		0	(2)
Dominion Energy Gas Holdings, LLC | NGL Midstream
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers		42	$ 26
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Other revenues		$ 8

[1] Amounts above include $14 million and $8 million of alternative revenue at Dominion Energy and Virginia Power for the three months ended March 31, 2019, respectively.