Derivative Instruments And Hedging Activities (Outstanding Energy Commodity Contracts Employed As Cash Flow Hedges) (Details) (Pepco Energy Services [Member])	Mar. 31, 2012	Dec. 31, 2011
Forecasted Purchases Hedges [Member] | Natural Gas (One Million British Thermal Units (MMBtu)) [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount
Forecasted Purchases Hedges [Member] | Electricity (Megawatt Hours (MWh)) [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	246,680	614,560
Forecasted Purchases Hedges [Member] | Electricity Capacity (MW-Days) [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount
Forecasted Sales Hedges [Member] | Electricity (Megawatt Hours (MWh)) [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	246,680	614,560