Commitments And Contingencies (Environmental Matters) (Details) (USD $)	0 Months Ended	1 Months Ended		3 Months Ended	1 Months Ended	3 Months Ended	1 Months Ended
	Jul. 02, 2010	Jan. 31, 2011 gal	Jul. 31, 2010	Mar. 31, 2012	Jul. 31, 2010 Conectiv Energy [Member]	Mar. 31, 2012 Conectiv Energy [Member]	Aug. 31, 2011 Potomac Electric Power Co [Member]	Feb. 29, 2012 Pepco Energy Services [Member]
Commitments And Contingencies [Line Items]
Third party maximum and seller floor for environmental remediation costs			$ 10,000,000		$ 10,000,000
Environmental remediation expense minimum	7,000,000
Environmental remediation expense maximum	18,000,000
Minimum estimated costs for closure of the operations						2,000,000
Maximum estimated costs for closure of the operations						3,000,000
Minimum estimated annual post closure operation, maintenance and monitoring costs, per year						120,000
Maximum estimated annual post closure operation, maintenance and monitoring costs, per year						193,000
Number of years that payments will be made to close coal ash landfill						30 years
EPA costs to date to clean up site				6,000,000
Estimated costs remaining to remediate the site				6,000,000
Penalty charges related to release of oil in U.S. waters				5,000
Quantity of mineral oil spill (gallons)		4,500
Civil penalty							$ 40,000	$ 10,000