Regulatory Matters - Schedule of Current Base Rate Increase Requisition to Increase Annual Revenue (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	1 Months Ended			0 Months Ended				1 Months Ended			3 Months Ended		0 Months Ended	3 Months Ended
	Mar. 26, 2014	Mar. 31, 2014	Jul. 31, 2012	Dec. 31, 2011	Mar. 26, 2014 Potomac Electric Power Co [Member]	Dec. 03, 2013 Potomac Electric Power Co [Member]	Jul. 12, 2013 Potomac Electric Power Co [Member]	Mar. 08, 2013 Potomac Electric Power Co [Member]	Nov. 30, 2012 Potomac Electric Power Co [Member]	Jul. 31, 2012 Potomac Electric Power Co [Member]	Dec. 31, 2011 Potomac Electric Power Co [Member]	Mar. 31, 2014 Potomac Electric Power Co [Member]	Mar. 31, 2014 Potomac Electric Power Co [Member] MD [Member]	Mar. 14, 2014 Atlantic City Electric Co [Member]	Mar. 31, 2014 Atlantic City Electric Co [Member]	Mar. 31, 2014 Atlantic City Electric Co [Member] NJ [Member]
Regulatory Matters [Line Items]
Requested rate change	$ 23.4	$ 61.7	$ 18.1			$ 44.8		$ 52.1	$ 60.8	$ 18.1	$ 68.4		$ 37.4	$ 61.7		$ 61.7
Return on equity, percentage	9.40%	10.25%	9.31%	10.75%	9.40%	10.25%	9.36%	10.25%	10.25%	9.31%	10.75%	10.80%	10.25%	10.25%	10.80%	10.25%
Initial Filing Date													Dec. 04, 2013			Mar. 14, 2014
Expected Timing of Decision													Q3, 2014			Q1, 2015