Variable Interest Entities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	12 Months Ended
	Oct. 18, 2011 Delmarva Power & Light Co/De [Member] Fuel Cell Facility [Member] MW	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Fuel Cell Facility [Member] MW	Dec. 31, 2012 Delmarva Power & Light Co/De [Member] Fuel Cell Facility [Member] MW	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Land-Based Wind PPA [Member] MW Agreement	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Solar PPA [Member] MW Agreement	Dec. 31, 2012 Delmarva Power & Light Co/De [Member] Solar PPA [Member]	Dec. 31, 2011 Delmarva Power & Light Co/De [Member] Solar PPA [Member]	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Wind PPA [Member]	Dec. 31, 2012 Delmarva Power & Light Co/De [Member] Wind PPA [Member]	Dec. 31, 2011 Delmarva Power & Light Co/De [Member] Wind PPA [Member]	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Wind PPA [Member] Wind Facility One [Member] MW	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Wind PPA [Member] Wind Facility Two [Member] MW	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Wind PPA [Member] Wind Facility Three [Member] MW	Dec. 31, 2013 Atlantic City Electric Co [Member] Agreement	Dec. 31, 2013 Atlantic City Electric Co [Member] Non-Utility Generators [Member] MW	Dec. 31, 2012 Atlantic City Electric Co [Member] Non-Utility Generators [Member]	Dec. 31, 2011 Atlantic City Electric Co [Member] Non-Utility Generators [Member]
Variable Interest Entity [Line Items]
Megawatts received from power purchase agreements (PPAs)				128	10										459
Number of purchase power agreements				3	1									3
Energy purchase maximum to be purchased											50	40	38
Purchased energy								$ 30	$ 27	$ 18					$ 206	$ 201	$ 206
Term of agreement, years					20 years
Obligated purchase amount of energy produced at the facility					70.00%
Solar energy purchases					3	2	1
Power of fuel cell facility	30	15	3
Term of agreement, years	21 years
Amount billed to distribution customers		23	4
Net power purchases with non-utility generators															$ 221	$ 206	$ 218
Equity ownership percentage														100.00%