Commitments and Contingencies (Narrative) (Details) (USD $)	1 Months Ended			3 Months Ended	12 Months Ended						1 Months Ended
	Jun. 30, 2013	Apr. 30, 2012 MW	Sep. 30, 2011 Party	Mar. 31, 2014 Site	Dec. 31, 2013	Mar. 31, 2014 Third Party and Equity Method Investee	Mar. 31, 2014 Third Party and Equity Method Investee Through 2019	Mar. 31, 2014 Minimum	Mar. 31, 2014 Maximum	Mar. 31, 2014 Virginia Electric and Power Company Site	Jul. 31, 2011 CAA MW Group State	Mar. 31, 2014 Remediation program
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									25
Number of groups of affected states											2
Number of parties issued UAO			22
Daily civil penalties for non compliance				$ 37,500
Number of former manufactured gas plant sites				17						3
Preliminary costs for options under evaluation for site, minimum												1,000,000
Preliminary costs for options under evaluation for site, maximum												22,000,000
National GHG reduction goal (percentage)	17.00%
Maximum period for consideration of CO2 emissions from biomass projects					3 years
Amount of civil penalty						69,000,000
Exposure under guarantees				4,358,000,000		54,000,000	80,000,000
Annual future contributions								4,000,000	19,000,000
Purchased surety bonds				148,000,000						60,000,000
Authorized issuance of standby letters of credit				$ 237,000,000						$ 53,000,000