Derivative Instruments And Hedging Activities (Narrative) (Detail) (USD $) In Millions, unless otherwise specified			3 Months Ended			3 Months Ended				3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012 Pepco Energy Services [Member]	Mar. 31, 2013 Pepco Energy Services [Member]	Dec. 31, 2012 Pepco Energy Services [Member]	Mar. 31, 2013 Pepco Energy Services [Member] Natural Gas Derivatives [Member]	Mar. 31, 2012 Pepco Energy Services [Member] Natural Gas Derivatives [Member]	Mar. 31, 2013 Delmarva Power & Light Co/De [Member]	Dec. 31, 2012 Delmarva Power & Light Co/De [Member]	Mar. 31, 2013 Atlantic City Electric Co [Member]	Dec. 31, 2012 Atlantic City Electric Co [Member]
Derivative losses included in AOCL						$ 2	$ 16
Credit risk derivative liabilities, at fair value	2	8						0	4
Credit risk derivative liabilities, at fair value net	2	8						0	4
Net settlement amount in the event of a downgrade below investment grade	24	40						0	2
Additional collateral that would have to be posted in the event of an investment downgrade	24	40						0	2
Cash plus borrowing capacity to meet future liquidity needs	975	861						635	477
Debt instrument unused borrowing capacity amount for subsidiary				340	384
Estimated percentage of New Jersey load										15.00%
Derivative assets (non-current assets)	8	8								8	8
Derivative assets (non-current liabilities)	11	11								11	11
Unrealized loss on derivatives			$ (4)							$ 0