Commitments and Contingencies - Schedule of Commitments and Obligations (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013
Commitments And Contingencies [Line Items]
Energy procurement obligations of Pepco Energy Services	$ 54
Guarantees associated with disposal of Conectiv Energy assets	13
Guaranteed lease residual values	18
Total	85
PHI [Member]
Commitments And Contingencies [Line Items]
Energy procurement obligations of Pepco Energy Services	54
Guarantees associated with disposal of Conectiv Energy assets	13
Guaranteed lease residual values	2
Total	69
Potomac Electric Power Co [Member]
Commitments And Contingencies [Line Items]
Guaranteed lease residual values	5
Total	5
Delmarva Power & Light Co/De [Member]
Commitments And Contingencies [Line Items]
Guaranteed lease residual values	7
Total	7
Atlantic City Electric Co [Member]
Commitments And Contingencies [Line Items]
Guaranteed lease residual values	4
Total	$ 4