Commitments and Contingencies (Narrative) (Details) (USD $)	1 Months Ended		6 Months Ended	12 Months Ended	6 Months Ended				6 Months Ended			1 Months Ended	6 Months Ended		6 Months Ended
	Feb. 28, 2013 T	Sep. 30, 2011 Party	Jun. 30, 2013 Site	Dec. 31, 2012 T	Jun. 30, 2013 Nuclear Obligations	Jun. 30, 2013 Third Party and Equity Method Investee	Jun. 30, 2013 Third Party and Equity Method Investee Through 2019	Jun. 30, 2013 September 2013	Jun. 30, 2013 September 2013 Nuclear Obligations	Jun. 30, 2013 Minimum	Jun. 30, 2013 Maximum	Jul. 31, 2011 CAA Group MW State	Jun. 30, 2013 CAA	Apr. 25, 2013 CAA	Jun. 30, 2013 Virginia Electric and Power Company Site
Investments in and Advances to Affiliates [Line Items]
Number of states under EPA replacement rule												28
Emissions of fossil fuel fired electric generating units (MW)												25
Number of groups of affected states												2
Amount of civil penalty						$ 90,000,000							$ 13,000,000	$ 3,000,000
Amount to fund environmental mitigation projects														10,000,000
Period for public comment (days)													30 days
Number of parties issued UAO		22
Daily civil penalties for non compliance			37,500
Number of former manufactured gas plant sites			17												3
Percent further emmision reduction goals in participating state power plant CO2 emissions (percentage)			10.00%
CO2 emissions cap	91,000,000			165,000,000
Percentage reduction in CO2 Emissions	2.50%
Liability protection per nuclear incident					12,600,000,000				13,600,000,000
Inflationary provision adjustment period			5 years
Coverage from commercial insurance pools			375,000,000
Amounts assessed for each licensed reactor			118,000,000					127,000,000
Amount assessed per year per reactor			18,000,000					19,000,000
Minimum requirement for nuclear power plant licenses per reactor site			1,060,000,000
Maximum retrospective premium assessment for nuclear power plant licensees			71,000,000												39,000,000
Maximum retrospective premium assessment for replacement power costs			19,000,000												9,000,000
Exposure under guarantees			4,281,000,000			60,000,000	97,000,000
Annual future contributions										4,000,000	19,000,000
Purchased surety bonds			146,000,000												56,000,000
Authorized issuance of standby letters of credit			$ 18,000,000												$ 2,000,000