Debt (Credit Facilities) (Details) (USD $)	0 Months Ended	9 Months Ended
	Aug. 01, 2011	Sep. 30, 2011	Dec. 31, 2010
Line of credit facility, maximum borrowing capacity	$ 1,500,000,000
Line of credit facility, expiration date	August 1, 2016
Letter of credit, sublimit		500,000,000
Line of credit facility, sublimit		750,000,000
Debt instrument variable interest rate, interest rate before LIBOR		0.50%
Debt instrument variable interest rate, interest rate in addition to one month LIBOR		1.00%
Maximum percentage of credit facility to be used to make same day borrowings		10.00%
Unsecured credit agreements		200,000,000
Borrowing capacity under the credit facilities		1,400,000,000	1,200,000,000
Combined cash and borrowings capacity		831,000,000	462,000,000
Bi-lateral unsecured credit agreements		364
Letters Of Credit [Member]
Maximum amount of credit used to increase Decrease Sublimits		1,250,000,000
Letters Of Credit [Member] | Pepco, ACE And DPL [Member]
Maximum amount of credit used to increase Decrease Sublimits		500,000,000
PHI [Member]
Line of credit facility, expiration date		October 26, 2011
Pepco, ACE And DPL [Member]
Line of credit facility, sublimit		$ 250,000,000