Earnings Per Share (Calculation of Basic and Diluted EPS) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Earnings Per Share [Line Items]
Net income attributable to Dominion Energy	$ 1,009	$ 975	$ 54	$ (680)	$ 641	$ 854	$ 449	$ 503	$ 1,358	$ 2,447	$ 2,999
Preferred stock dividends (see Note 19)									(17)
Net income attributable to Dominion Energy - Basic									1,341	2,447	2,999
Dilutive effect of Series A Preferred Stock									(28)
Net income attributable to Dominion Energy - Diluted									$ 1,313	$ 2,447	$ 2,999
Average shares of common stock outstanding – Basic									808.8	654.2	636.0
Net effect of dilutive securities									0.1	0.7
Average shares of common stock outstanding – Diluted									808.9	654.9	636.0
Earnings Per Common Share – Basic	$ 1.22	$ 1.19	$ 0.07	$ (0.86)	$ 0.97	$ 1.31	$ 0.69	$ 0.77	$ 1.66	$ 3.74	$ 4.72
Earnings Per Common Share – Diluted	$ 1.21	$ 1.17	$ 0.05	$ (0.86)	$ 0.97	$ 1.30	$ 0.69	$ 0.77	$ 1.62	$ 3.74	$ 4.72