Debt (Financing Activities) (Details) (USD $)	0 Months Ended		6 Months Ended		1 Months Ended				6 Months Ended					6 Months Ended	0 Months Ended
	Aug. 01, 2011	Apr. 05, 2011	Jun. 30, 2011	Aug. 31, 2011	Jul. 31, 2011 ACE [Member] Series 2002-1 Bonds [Member]	Apr. 30, 2011 ACE [Member] Series 2002-1 Bonds [Member]	Jul. 31, 2011 ACE [Member] Series 2003-1 Bonds [Member]	Apr. 30, 2011 ACE [Member] Series 2003-1 Bonds [Member]	Jun. 30, 2011 Pepco [Member] Letters Of Credit [Member]	Jun. 30, 2011 Delmarva Power & Light Co/De [Member] Letters Of Credit [Member]	Jun. 30, 2011 Letters Of Credit [Member]	Jun. 30, 2011 Letters Of Credit [Member] Pepco, ACE and DPL [Member]	Jun. 30, 2011 Pepco, ACE and DPL [Member]	Jun. 30, 2011 ACE [Member]	Jun. 02, 2011 Delmarva Power & Light Co/De [Member]	May 02, 2011 Delmarva Power & Light Co/De [Member]
Purchase of mortgage bonds														$ 200,000,000
Remarketed tax-exempt bonds															35,000,000
Debt instruments, due date	May 02, 2012	Apr. 01, 2021	Aug. 01, 2016													May 01, 2026
Debt instrument, interest rate, stated percentage														4.35%	0.75%
Funding made principal payments					6,000,000	6,000,000	2,000,000	2,000,000
Letter of credit, sublimit			500,000,000
Line of credit facility, sublimit			750,000,000										250,000,000
Maximum amount of credit used to increase Decrease Sublimits									500,000,000	500,000,000	1,250,000,000	500,000,000
Line of credit facility, maximum borrowing capacity			$ 1,500,000,000	$ 1,500,000,000
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%