Regulatory Matters (Narrative) (Details) MMBTU in Thousands, $ in Millions	1 Months Ended										12 Months Ended
	Oct. 31, 2016 USD ($) program	Sep. 30, 2016 USD ($)	Aug. 31, 2016 USD ($) MMBTU	Jun. 30, 2016 USD ($)	May 31, 2016 USD ($) kV mi	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Aug. 31, 2009 kV	Apr. 30, 2008	Apr. 30, 2007 kV	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2008	Nov. 30, 2016 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory asset		$ 2,393											$ 2,216
Virginia Electric and Power Company
Public Utilities, General Disclosures [Line Items]
ROE (percentage)									11.40%
Regulatory asset		1,094											993
Virginia Electric and Power Company | Minimum
Public Utilities, General Disclosures [Line Items]
Facility operating capacity (kV) | kV								500		500
Virginia Electric and Power Company | FERC Gas Regulation | Order Regarding Transmission Rate Design for Allocation of Costs among PJM Interconnect LLC Transmission Customers | Unfavorable Regulatory Action | Settled Litigation
Public Utilities, General Disclosures [Line Items]
Amount required to pay under settlement agreement				$ 200
Duration of payment under settlement agreement				10 years
Virginia Electric and Power Company | FERC Gas Regulation | Order Regarding Transmission Rate Design for Allocation of Costs among PJM Interconnect LLC Transmission Customers | Unfavorable Regulatory Action | Settled Litigation | Regulatory asset recovered through retail rates
Public Utilities, General Disclosures [Line Items]
Regulatory asset		192
Virginia Electric and Power Company | FERC Gas Regulation | Order Regarding Transmission Rate Design for Allocation of Costs among PJM Interconnect LLC Transmission Customers | Unfavorable Regulatory Action | Settled Litigation | Other operations and maintenance | Regulatory asset recovered through retail rates
Public Utilities, General Disclosures [Line Items]
Remaining amount recorded in other operations and maintenance expense													8
Virginia Electric and Power Company | FERC Gas Regulation | Order Regarding Transmission Rate Design for Allocation of Costs among PJM Interconnect LLC Transmission Customers | Unfavorable Regulatory Action | Settled Litigation | Other deferred credits and other liabilities
Public Utilities, General Disclosures [Line Items]
Amount of contingent liability		200
Virginia Electric and Power Company | Virginia Regulation
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement					$ 1,400
Proposed revenue requirement increase (decrease)					$ (286)
Virginia Electric and Power Company | Virginia Regulation | North Anna | Intent to Sue Notification Received from Sierra Club Alleging Endangered Species Act Violations
Public Utilities, General Disclosures [Line Items]
Period of notice of intent to sue			60 days
Virginia Electric and Power Company | Virginia Regulation | Phase One of Cost Recovery to Move Electric Distribution Facilities Underground
Public Utilities, General Disclosures [Line Items]
Total projected capital investment			$ 140
Virginia Electric and Power Company | Virginia Regulation | Poland Road Substation
Public Utilities, General Disclosures [Line Items]
Capacity of transmission line (kV) | kV					230
Virginia Electric and Power Company | Virginia Regulation | Double Circuit Transmission Line between Loudoun-Brambleton Line and Poland Road Substation
Public Utilities, General Disclosures [Line Items]
Capacity of transmission line (kV) | kV					230
Length of kV line (miles) | mi					4
Virginia Electric and Power Company | Virginia Regulation | Loudoun- Brambleton Line
Public Utilities, General Disclosures [Line Items]
Capacity of transmission line (kV) | kV					230
Virginia Electric and Power Company | Virginia Regulation | Rider U
Public Utilities, General Disclosures [Line Items]
ROE (percentage)			9.60%
Approved revenue required			$ 20
Virginia Electric and Power Company | Virginia Regulation | Rider U | Phase One of Cost Recovery to Move Electric Distribution Facilities Underground
Public Utilities, General Disclosures [Line Items]
Amount of cost recovery			123
Virginia Electric and Power Company | Virginia Regulation | Rider U, 2017-2018 Rate Year
Public Utilities, General Disclosures [Line Items]
Projected capital investment			2
Virginia Electric and Power Company | Virginia Regulation | Rider U, 2018-2019 Rate Year
Public Utilities, General Disclosures [Line Items]
Projected capital investment			2
Virginia Electric and Power Company | Virginia Regulation | Subsequent Event | Rider BW
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement	$ 134
Proposed revenue requirement increase (decrease)	14
Virginia Electric and Power Company | Virginia Regulation | Subsequent Event | Rider US-2
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement	10
Proposed revenue requirement increase (decrease)	6
Virginia Electric and Power Company | Virginia Regulation | Subsequent Event | Riders C1A and C2A
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement	$ 45
Virginia Electric and Power Company | Virginia Regulation | Subsequent Event | Riders C1A and C2A | Energy Efficiency Program
Public Utilities, General Disclosures [Line Items]
Number of new energy efficiency programs | program	2
Period of cost cap	5 years
Duration of program	2 years
Virginia Electric and Power Company | Virginia Regulation | Subsequent Event | Riders C1A and C2A | Peak Shaving Program
Public Utilities, General Disclosures [Line Items]
Duration of program	5 years
Virginia Electric and Power Company | Virginia Regulation | Subsequent Event | Maximum | Riders C1A and C2A | Energy Efficiency Program
Public Utilities, General Disclosures [Line Items]
Amount of cost recovery	$ 178
Virginia Electric and Power Company | Virginia Regulation | Subsequent Event | Maximum | Riders C1A and C2A | Peak Shaving Program
Public Utilities, General Disclosures [Line Items]
Amount of cost recovery	$ 5
Virginia Electric and Power Company | North Carolina Regulation
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement increase (decrease)			$ (36)
Virginia Electric and Power Company | North Carolina Regulation | Annual Non- Fuel Base Revenues
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement increase (decrease)						$ 51
Proposed ROE percentage						10.50%
Virginia Electric and Power Company | North Carolina Regulation | Subsequent Event | Annual Non- Fuel Base Revenues
Public Utilities, General Disclosures [Line Items]
Proposed ROE percentage	9.90%
Base rate increase per stipulation and settlement agreement	$ 35
East Ohio | Ohio Regulation | PIR
Public Utilities, General Disclosures [Line Items]
Total projected capital investment							$ 200
Percentage of pipeline system														25.00%
Period for capital investment							5 years
Percentage increase in capital spend							3.00%
East Ohio | Ohio Regulation | Subsequent Event | PSMP | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Total projected capital investment															$ 15
Hope Gas Inc | West Virginia Regulation | PREP
Public Utilities, General Disclosures [Line Items]
Amount of cost recovery		2
Total projected capital investment					$ 152
Period for capital investment					5 years
Hope Gas Inc | West Virginia Regulation | PREP | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Projected capital investment											$ 27	$ 20
Dominion Gas Holdings, LLC
Public Utilities, General Disclosures [Line Items]
Regulatory asset		$ 491											$ 472
Dominion Gas Holdings, LLC | FERC Gas Regulation | Leidy South Project Facilities
Public Utilities, General Disclosures [Line Items]
Duration of contracts			20 years
Amount of project			$ 210
Daily firm transportation service (Dths) | MMBTU			155