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				12 Months Ended
	Dec. 04, 2013	Jul. 12, 2013	Mar. 08, 2013	Nov. 30, 2012	Jul. 31, 2012	Dec. 31, 2013	Dec. 31, 2011
Potomac Electric Power Co [Member]
Regulatory Matters [Line Items]
Requested rate change			$ 44.8	$ 60.8	$ 18.1
Return on equity, percentage	10.25%	9.36%	10.25%	10.25%	9.31%	10.80%	10.75%
Potomac Electric Power Co [Member] | District of Columbia [Member]
Regulatory Matters [Line Items]
Requested rate change						44.8
Return on equity, percentage						10.25%
Initial Filing Date						Mar. 08, 2013
Expected Timing of Decision						Q1-2014
Potomac Electric Power Co [Member] | MD [Member]
Regulatory Matters [Line Items]
Requested rate change						43.3
Return on equity, percentage						10.25%
Initial Filing Date						Dec. 04, 2013
Expected Timing of Decision						Q3-2014
Delmarva Power Light Co Electric [Member] | DE [Member]
Regulatory Matters [Line Items]
Requested rate change						$ 39.0
Return on equity, percentage						10.25%
Initial Filing Date						Mar. 22, 2013
Expected Timing of Decision						Q2-2014