Related Party Transactions (Schedule Of Related Party Transactions Included In Balance Sheet) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Potomac Electric Power Co [Member]
Related Party Transaction [Line Items]
(Payable to ) Receivable from Related Party (current)	$ (55)	[1]	$ (57)	[1]
Potomac Electric Power Co [Member] | PHI Parent Company [Member]
Related Party Transaction [Line Items]
(Payable to ) Receivable from Related Party (current)			15	[1]
Potomac Electric Power Co [Member] | Phi Service Company [Member]
Related Party Transaction [Line Items]
(Payable to ) Receivable from Related Party (current)	(30)	[1]	(32)	[1]
Potomac Electric Power Co [Member] | Pepco Energy Services [Member]
Related Party Transaction [Line Items]
(Payable to ) Receivable from Related Party (current)	(25)	[1],[2]	(40)	[1],[2]
Atlantic City Electric Co [Member]
Related Party Transaction [Line Items]
(Payable to ) Receivable from Related Party (current)	(16)	[1]	(14)	[1]
Atlantic City Electric Co [Member] | Phi Service Company [Member]
Related Party Transaction [Line Items]
(Payable to ) Receivable from Related Party (current)	(15)	[1]	(12)	[1]
Atlantic City Electric Co [Member] | Other Related Party [Member]
Related Party Transaction [Line Items]
(Payable to ) Receivable from Related Party (current)	(1)	[1]	(2)	[1]
Delmarva Power & Light Co/De [Member]
Related Party Transaction [Line Items]
(Payable to ) Receivable from Related Party (current)	(23)	[1]	(21)	[1]
Delmarva Power & Light Co/De [Member] | Phi Service Company [Member]
Related Party Transaction [Line Items]
(Payable to ) Receivable from Related Party (current)	(23)	[1]	(20)	[1]
Delmarva Power & Light Co/De [Member] | Conectiv Energy Supply, Inc. [Member]
Related Party Transaction [Line Items]
(Payable to ) Receivable from Related Party (current)			$ (1)	[1]

[1] Included in Accounts payable due to associated companies.

[2] Pepco bills customers on behalf of Pepco Energy Services where customers have selected Pepco Energy Services as their alternative energy supplier or where Pepco Energy Services has performed work for certain government agencies under a General Services Administration area-wide agreement.