Earnings Per Share (Calculation of Basic and Diluted EPS) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income attributable to Dominion Energy	$ 503	$ 632
Average shares of common stock outstanding – Basic	650.5	628.1
Average shares of common stock outstanding – Diluted	650.5	628.1
Earnings Per Common Share – Basic	$ 0.77	$ 1.01
Earnings Per Common Share – Diluted	$ 0.77	$ 1.01