Regulatory Matters - Schedule of Current Base Rate Approval to Increase Annual Revenue (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		1 Months Ended		9 Months Ended
	Sep. 30, 2013 Atlantic City Electric Co [Member] NJ [Member]	Sep. 30, 2013 Potomac Electric Power Co [Member] MD [Member]	Aug. 27, 2013 Delmarva Power & Light Co/De [Member]	Aug. 30, 2013 Delmarva Power & Light Co/De [Member]	Sep. 30, 2013 Delmarva Power & Light Co/De [Member] MD [Member]	Sep. 30, 2013 Delmarva Power Light Co Gas [Member] DE [Member]
Regulatory Matters [Line Items]
Approved Revenue Requirement Increase	$ 25.5	$ 27.9	$ 6.8	$ 15.0	$ 15.0	$ 6.8
Approved Return on Equity	9.75%	9.36%	9.75%		9.81%	9.75%
Completion Date	Jun. 21, 2013	Jul. 12, 2013			Aug. 30, 2013	Oct. 22, 2013
Rate Effective Date	Jul. 01, 2013	Jul. 12, 2013			Sep. 15, 2013	Nov. 01, 2013