Commitments And Contingencies (Environmental Matters) (Details) (USD $)	0 Months Ended	12 Months Ended		1 Months Ended	0 Months Ended
	Jan. 23, 2011 gal	Dec. 31, 2011	Dec. 31, 2011 Atlantic City Electric Co [Member]	Aug. 31, 2011 Potomac Electric Power Co [Member]	Feb. 06, 2012 Pepco Energy Services [Member]
EPA costs to date to clean up site		$ 6,000,000
Estimated costs remaining to remediate the site		6,000,000
Settlement agreement payment			1,000,000
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