Operating Revenue (Schedule of Operating Revenue For Revised Guidance of Revenue Recognition From Contracts with Customers ) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Public Utilities General Disclosures [Line Items]
Total operating revenue	[1]	$ 3,088	$ 2,813	$ 6,554	$ 6,197
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Total operating revenue	[2]	1,829	1,747	3,577	3,578
Dominion Energy Gas Holdings, LLC
Public Utilities General Disclosures [Line Items]
Total operating revenue	[3]	$ 459	422	$ 985	912
Prior to adoption of revised guidance
Public Utilities General Disclosures [Line Items]
Nonregulated			307		734
Regulated			151		599
Nonregulated			110		254
Total operating revenue			2,813		6,197
Prior to adoption of revised guidance | Regulated Electric Sales
Public Utilities General Disclosures [Line Items]
Revenue			1,716		3,482
Prior to adoption of revised guidance | Gas Transportation and Storage
Public Utilities General Disclosures [Line Items]
Revenue			430		922
Prior to adoption of revised guidance | Other
Public Utilities General Disclosures [Line Items]
Revenue			99		206
Prior to adoption of revised guidance | Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Total operating revenue			1,747		3,578
Prior to adoption of revised guidance | Virginia Electric and Power Company | Regulated Electric Sales
Public Utilities General Disclosures [Line Items]
Revenue			1,716		3,482
Prior to adoption of revised guidance | Virginia Electric and Power Company | Other
Public Utilities General Disclosures [Line Items]
Revenue			31		96
Prior to adoption of revised guidance | Dominion Energy Gas Holdings, LLC
Public Utilities General Disclosures [Line Items]
Regulated			15		47
Nonregulated			8		10
Total operating revenue			422		912
Prior to adoption of revised guidance | Dominion Energy Gas Holdings, LLC | Gas Transportation and Storage
Public Utilities General Disclosures [Line Items]
Revenue			342		738
Prior to adoption of revised guidance | Dominion Energy Gas Holdings, LLC | Other
Public Utilities General Disclosures [Line Items]
Revenue			$ 57		$ 117

[1] See Note 10 for amounts attributable to related parties.

[2] See Note 18 for amounts attributable to affiliates.

[3] See Note 18 for amounts attributable to related parties.