Related Party Transactions - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Atlantic City Electric Co [Member]
Related Party Transaction [Line Items]
Capital contribution from Parent	$ 75		$ 60
Atlantic City Electric Co [Member] | Conectiv Energy [Member]
Related Party Transaction [Line Items]
Capital contribution from Parent			60
Atlantic City Electric Co [Member] | PHI Service Company [Member]
Related Party Transaction [Line Items]
Costs directly charged or allocated	115	117	102
Potomac Electric Power Co [Member]
Related Party Transaction [Line Items]
Capital contribution from Parent	175	50
Potomac Electric Power Co [Member] | PHI Service Company [Member]
Related Party Transaction [Line Items]
Costs directly charged or allocated	209	211	185
Potomac Electric Power Co [Member] | Pepco Energy Services [Member]
Related Party Transaction [Line Items]
Maintenance services	20	16	20
Delmarva Power & Light Co/De [Member]
Related Party Transaction [Line Items]
Capital contribution from Parent		60
Delmarva Power & Light Co/De [Member] | PHI Service Company [Member]
Related Party Transaction [Line Items]
Costs directly charged or allocated	$ 154	$ 153	$ 133