Equity (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Common stock, par value	$ 0
Common stock, shares authorized	50,000,000
Common stock, shares issued	40,300,000
Common stock, shares outstanding	40,300,000	40,300,000
Preferred stock, par value	$ 0
Preferred stock, shares authorized	20,000,000
Preferred stock, shares issued	1,000
Preferred stock, shares outstanding	1,000
Contributions from SCANA	$ 838	$ 24	$ 3
Retained earnings, restricted	115	$ 115
Dominion Energy
Class Of Stock [Line Items]
Contributions from SCANA	$ 835