Operative Revenue (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenues From Contract With Customer [Line Items]
Contract asset balances	$ 28	$ 42
Contract liability balances	123	106
Revenue recognized from contract liability balances	94
Dominion Energy Gas Holdings, LLC
Revenues From Contract With Customer [Line Items]
Contract asset balances	40	58
Contract liability balances	20	28
Revenue recognized from contract liability balances	8	3
Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Contract liability balances	24	22
Revenue recognized from contract liability balances	$ 22	$ 25