Operating Revenue (Schedule of Operating Revenue For Revised Guidance of Revenue Recognition From Contracts with Customers ) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Public Utilities General Disclosures [Line Items]
Total operating revenue	[1]	$ 3,451	$ 3,179	$ 10,005	$ 9,376
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Total operating revenue	[2]	2,232	2,154	5,809	5,732
Dominion Energy Gas Holdings, LLC
Public Utilities General Disclosures [Line Items]
Total operating revenue	[3]	$ 423	401	$ 1,408	1,313
Prior to adoption of revised guidance
Public Utilities General Disclosures [Line Items]
Nonregulated			380		1,114
Regulated			97		696
Nonregulated			69		323
Total operating revenue			3,179		9,376
Prior to adoption of revised guidance | Regulated Electric Sales
Public Utilities General Disclosures [Line Items]
Revenue			2,108		5,590
Prior to adoption of revised guidance | Gas Transportation and Storage
Public Utilities General Disclosures [Line Items]
Revenue			406		1,328
Prior to adoption of revised guidance | Other
Public Utilities General Disclosures [Line Items]
Revenue			119		325
Prior to adoption of revised guidance | Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Total operating revenue			2,154		5,732
Prior to adoption of revised guidance | Virginia Electric and Power Company | Regulated Electric Sales
Public Utilities General Disclosures [Line Items]
Revenue			2,108		5,590
Prior to adoption of revised guidance | Virginia Electric and Power Company | Other
Public Utilities General Disclosures [Line Items]
Revenue			46		142
Prior to adoption of revised guidance | Dominion Energy Gas Holdings, LLC
Public Utilities General Disclosures [Line Items]
Regulated			12		59
Nonregulated			2		12
Total operating revenue			401		1,313
Prior to adoption of revised guidance | Dominion Energy Gas Holdings, LLC | Gas Transportation and Storage
Public Utilities General Disclosures [Line Items]
Revenue			324		1,062
Prior to adoption of revised guidance | Dominion Energy Gas Holdings, LLC | Other
Public Utilities General Disclosures [Line Items]
Revenue			$ 63		$ 180

[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.