Goodwill and Intangible Assets (Goodwill) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	$ 7,395	$ 4,859
SCANA Combination	[2]		2,609
Contribution	[3]	(14)
Goodwill, Ending Balance	[1]	7,381	7,395
SCANA
Goodwill [Roll Forward]
Goodwill, Beginning Balance		2,609
Contribution	[3]		(73)
Goodwill, Ending Balance			2,609
Corporate and Other
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	14	14
SCANA Combination	[2]		73
Contribution	[3]	(14)
Goodwill, Ending Balance	[1]		14
Corporate and Other | SCANA
Goodwill [Roll Forward]
Contribution	[3]		(73)
Operating Segments | Dominion Energy Virginia
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	2,106	2,106
Goodwill, Ending Balance	[1]	2,106	2,106
Operating Segments | Gas Distribution
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	3,512	2,497
SCANA Combination	[2]		1,015
Goodwill, Ending Balance	[1]	3,512	3,512
Operating Segments | Dominion Energy South Carolina
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	1,521
SCANA Combination	[2]		1,521
Goodwill, Ending Balance	[1]	1,521	1,521
Operating Segments | Contracted Assets
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	242	242
Goodwill, Ending Balance	[1]	$ 242	$ 242

[1] Goodwill amounts do not contain any accumulated impairment losses.

[2] See Note 3 for more information on the SCANA Combination. As a result of the December 2019 segment realignment, the acquired goodwill was reassigned using a relative fair value approach.

[3] See Note 9 for additional information including amounts reclassified to held for sale at December 31, 2020.