Goodwill and Intangible Assets (Goodwill) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	$ 6,405	$ 6,399
Purchase Accounting Adjustment		5
Dominion Questar Combination			6
Goodwill, Ending Balance	[1]	6,410	6,405
Dominion Energy Gas Holdings, LLC
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	542	542
Purchase Accounting Adjustment		5
No events affecting goodwill			0
Goodwill, Ending Balance	[1]	547	542
Operating Segments | Power Generation
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	1,422	1,422
Goodwill, Ending Balance	[1]	1,422	1,422
Operating Segments | Gas Infrastructure
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	4,057	4,051
Purchase Accounting Adjustment		5
Dominion Questar Combination	[2]		6
Goodwill, Ending Balance	[1]	4,062	4,057
Operating Segments | Power Delivery
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	926	926
Goodwill, Ending Balance	[1]	926	926
Operating Segments | Dominion Energy Gas Holdings, LLC | Power Generation
Goodwill [Roll Forward]
No events affecting goodwill			0
Operating Segments | Dominion Energy Gas Holdings, LLC | Gas Infrastructure
Goodwill [Roll Forward]
Goodwill, Beginning Balance	[1]	542	542
Purchase Accounting Adjustment		5
No events affecting goodwill			0
Goodwill, Ending Balance	[1]	$ 547	542
Operating Segments | Dominion Energy Gas Holdings, LLC | Power Delivery
Goodwill [Roll Forward]
No events affecting goodwill			0
Operating Segments | Dominion Energy Gas Holdings, LLC | Corporate and Other
Goodwill [Roll Forward]
No events affecting goodwill	[3]		$ 0

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

[2] See Note 3.

[3] Goodwill recorded at the Corporate and Other segment is allocated to the primary operating segments for goodwill impairment testing purposes.