Operating Revenue (Narrative) (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenues From Contract With Customer [Line Items]
Contract asset balances	$ 25		$ 28
Contract liability balances	109		123
Revenue recognized from contract liability balances	106	$ 91
Dominion Energy Gas Holdings, LLC
Revenues From Contract With Customer [Line Items]
Contract asset balances	35		40
Contract liability balances	21		20
Revenue recognized from contract liability balances	1	28
Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Contract liability balances	37		$ 24
Revenue recognized from contract liability balances	$ 24	$ 22