Related Party Transactions (Schedule Of Related Party Transactions Included In Income Statement) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Delmarva Power & Light Co/De [Member]
Related Party Transaction [Line Items]
Intercompany lease transactions	$ 1	[1]	$ 1	[1]
Atlantic City Electric Co [Member] | Millennium Account Services LLC (ACE Affiliate) [Member]
Related Party Transaction [Line Items]
Amounts of transaction	$ (1)	[2]	$ (1)	[2]

[1] Included in Electric revenue.

[2] Included in Other Operation and Maintenance expense.