Regulatory Matters (Narrative) (Details) $ in Millions		1 Months Ended							6 Months Ended	12 Months Ended
	Jul. 31, 2016 USD ($)	Aug. 31, 2016 USD ($) MW	Jun. 30, 2016 USD ($)	May 31, 2016 USD ($)	Oct. 31, 2015 USD ($) MW	Aug. 31, 2009 kV	Apr. 30, 2008	Apr. 30, 2007 kV	Jun. 30, 2016 USD ($) power_station	Dec. 31, 2015 USD ($)
Regulatory Matters [Line Items]
Regulatory asset			$ 2,371						$ 2,371	$ 2,216
Virginia Electric and Power Company
Regulatory Matters [Line Items]
ROE (percentage)							11.40%
Facility operating capacity (kV) | kV						500		500
Regulatory asset			1,159						1,159	993
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 Matters [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
Regulatory Matters [Line Items]
Regulatory asset			$ 192						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
Regulatory Matters [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
Regulatory Matters [Line Items]
Amount of contingent liability			200						$ 200
Virginia Electric and Power Company | Virginia Regulation
Regulatory Matters [Line Items]
Amount of fuel revenue decrease				$ 286
Virginia Electric and Power Company | Virginia Regulation | Rider S
Regulatory Matters [Line Items]
Proposed revenue requirement			254
Revenue requirement increase (decrease)			3
Virginia Electric and Power Company | Virginia Regulation | Rider R
Regulatory Matters [Line Items]
Proposed revenue requirement			75
Revenue requirement increase (decrease)			1
Virginia Electric and Power Company | Virginia Regulation | Rider W
Regulatory Matters [Line Items]
Proposed revenue requirement			126
Revenue requirement increase (decrease)			9
Virginia Electric and Power Company | Virginia Regulation | Rider B
Regulatory Matters [Line Items]
Proposed revenue requirement			28
Revenue requirement increase (decrease)			(1)
Number of power stations converted to biomass | power_station									3
Virginia Electric and Power Company | Virginia Regulation | Rider GV
Regulatory Matters [Line Items]
Proposed revenue requirement			89
Revenue requirement increase (decrease)			$ 49
Virginia Electric and Power Company | Virginia Regulation | Rider BW
Regulatory Matters [Line Items]
ROE (percentage)			10.60%
Approved revenue required			$ 119
Virginia Electric and Power Company | Virginia Regulation | Rider T1
Regulatory Matters [Line Items]
Proposed revenue requirement				639
Revenue requirement increase (decrease)				1
Virginia Electric and Power Company | Virginia Regulation | Solar Development Project | Subsequent Event | Scenario, Forecast
Regulatory Matters [Line Items]
Capacity of solar facility (mw) | MW		18
Total estimated cost		$ 40
Virginia Electric and Power Company | Virginia Regulation | Solar Development Project | Rider US-2
Regulatory Matters [Line Items]
ROE (percentage)			9.60%
Capacity of solar facility (mw) | MW					56
Total estimated cost					$ 130
Approved revenue required			$ 4
East Ohio | Ohio Regulation | UEX Rider
Regulatory Matters [Line Items]
Refund of accumulated bad debt expense				8
Net bad debt expense				19
East Ohio | Ohio Regulation | Subsequent Event | PIPP Plus Program
Regulatory Matters [Line Items]
Projected deferred program costs	$ 32
Refund of over-recovery of accumulated arrearages	$ 28
Hope Gas Inc | West Virginia Regulation | PREP
Regulatory Matters [Line Items]
Projected capital investment				$ 27
Period for capital investment				5 years
Total projected capital investment				$ 152
DCG | FERC Gas Regulation | Columbia to Eastover Project
Regulatory Matters [Line Items]
Amount of project			$ 45