Derivative Instruments And Hedging Activities (Net Outstanding Natural Gas Commodity Forward Contracts That Did Not Qualify For Hedge Accounting) (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Financial Transmission Rights (MWh) [Member] | Pepco Energy Services [Member]
Derivative [Line Items]
Commodity forward contracts	79,607	267,480
Net Position	Long	Long
Electric Capacity (MW-Days) [Member] | Pepco Energy Services [Member]
Derivative [Line Items]
Commodity forward contracts	5,185	12,920
Net Position	Long	Long
Electricity (Megawatt Hours (MWh)) [Member] | Pepco Energy Services [Member]
Derivative [Line Items]
Commodity forward contracts	657,240	788,280
Net Position	Long	Long
Natural Gas (One Million British Thermal Units (MMBtu)) [Member] | Pepco Energy Services [Member]
Derivative [Line Items]
Commodity forward contracts	15,037,300	24,550,257
Net Position	Long	Long
Natural Gas (One Million British Thermal Units (MMBtu)) [Member] | Delmarva Power & Light Co/De [Member]
Derivative [Line Items]
Commodity forward contracts	4,109,100	6,161,200
Net Position	Long	Long