Derivative Instruments And Hedging Activities (Net Outstanding Natural Gas Commodity Forward Contracts Not Qualified For Hedge Accounting) (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Pepco Energy Services [Member] | Electricity (Mwh) [Member]
Net Position	Long	Short
Commodity forward contracts	1,106,232	1,455,800
Pepco Energy Services [Member] | Electric Capacity (MW-Days) [Member]
Net Position	Long	Short
Commodity forward contracts	28,560	2,265
Pepco Energy Services [Member] | Financial Transmission Rights (MWh) [Member]
Net Position	Long	Long
Commodity forward contracts	619,226	381,215
Pepco Energy Services [Member] | Natural Gas (MMBtu) [Member]
Net Position	Long	Short
Commodity forward contracts	36,003,000	45,889,486
Delmarva Power & Light Co/De [Member] | Natural Gas (MMBtu) [Member]
Net Position	Long	Long
Commodity forward contracts	5,892,432	7,827,635