Regulatory Matters (Details) (USD $)	1 Months Ended	3 Months Ended	12 Months Ended				0 Months Ended		1 Months Ended		0 Months Ended	3 Months Ended		0 Months Ended				0 Months Ended
	Aug. 31, 2011	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 12, 2012 MW	Jan. 31, 2012 Delmarva Power & Light Co/De [Member]	Dec. 09, 2011 Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 Delmarva Power & Light Co/De [Member]	Jul. 02, 2012 Delmarva Power & Light Co/De [Member]	Aug. 05, 2011 Atlantic City Electric Co [Member]	Mar. 31, 2012 Atlantic City Electric Co [Member]	Sep. 30, 2011 Atlantic City Electric Co [Member]	Dec. 16, 2011 Potomac Electric Power Co [Member]	Jul. 08, 2011 Potomac Electric Power Co [Member]	Apr. 12, 2012 Minimum [Member] MW	Apr. 12, 2012 Maximum [Member] MW	Feb. 24, 2012 Maximum [Member] Atlantic City Electric Co [Member]
Regulatory Matters [Line Items]
Effect of proposed change on gas cost rate	5.60%
Requested rate change								$ 25,200,000	$ 31,800,000		$ 90,300,000			$ 68,400,000	$ 42,000,000
Return on equity, percentage								10.75%	10.75%		10.75%			10.75%	10.75%
Rate increase implemented							2,500,000
Under-recovery rate that would increase gas cost rates		6.00%
Contingent rate increase										29,300,000
Requested rate change, net											58,900,000							80,200,000
Base rate change related to excess depreciation											17,000,000
Base rate change related to increase in sales and use taxes											6,300,000
Base rate change related to regulatory asset recovery charge adjustment											600,000
Estimated recoverable capital expenditures			81,000,000	94,000,000	63,000,000
Incremental storm costs													8,000,000
Projected deferred under-recovered balance related to non-utility generators												113,800,000
Overall annual rate increase of the projected deferred under-recovered balance related to non-utility generators												$ 54,500,000
New power plant output						661										650	700