Operating Revenue (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenues From Contract With Customer [Line Items]
Contract asset balances	$ 26		$ 28
Contract liability balances	86		123
Revenue recognized from contract liability balances	105	$ 85
Dominion Energy Gas Holdings, LLC
Revenues From Contract With Customer [Line Items]
Contract asset balances	37		40
Contract liability balances	21		20
Revenue recognized from contract liability balances	1	25
Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Contract liability balances	23		$ 24
Revenue recognized from contract liability balances	$ 24	$ 22