Consolidated Statement Of Equity (USD $) In Millions, except Share data	Total USD ($)	Common Stock [Member] USD ($)	Premium On Stock [Member] USD ($)	Accumulated Other Comprehensive Loss [Member] USD ($)	Retained Earnings [Member] USD ($)	Delmarva Power & Light Co/De [Member] USD ($)	Delmarva Power & Light Co/De [Member] Common Stock [Member]	Delmarva Power & Light Co/De [Member] Premium On Stock [Member] USD ($)	Delmarva Power & Light Co/De [Member] Retained Earnings [Member] USD ($)	Atlantic City Electric Co [Member] USD ($)	Atlantic City Electric Co [Member] Common Stock [Member] USD ($)	Atlantic City Electric Co [Member] Premium On Stock [Member] USD ($)	Atlantic City Electric Co [Member] Retained Earnings [Member] USD ($)	Potomac Electric Power Co [Member] USD ($)	Potomac Electric Power Co [Member] Common Stock [Member]	Potomac Electric Power Co [Member] Premium On Stock [Member] USD ($)	Potomac Electric Power Co [Member] Retained Earnings [Member] USD ($)
BALANCE at Dec. 31, 2011	$ 4,336	$ 2	$ 3,325	$ (63)	$ 1,072	$ 852		$ 347	$ 505	$ 802	$ 26	$ 576	$ 200	$ 1,502		$ 705	$ 797
Common Stock, Shares, Outstanding at Dec. 31, 2011	227,500,190	227,500,190				1,000	1,000			8,546,017	8,546,017			100	100
Net income	68				68	21			21	2			2	24			24
Other comprehensive income	8			8
Dividends on common stock	(61)				(61)
Original issue shares, net	9		9
Original issue shares, net, shares		319,037
Shareholder DRP original shares, value	8		8
Shareholder DRP original shares, shares		424,888
Net activity related to stock-based awards	(2)		(2)
BALANCE at Mar. 31, 2012	4,366	2	3,340	(55)	1,079	873		347	526	804	26	576	202	1,526			821
Common Stock, Shares, Outstanding at Mar. 31, 2012		228,244,115					1,000				8,546,017				100
BALANCE at Dec. 31, 2011	4,336					852		347		802	26	576		1,502		705
Common Stock, Shares, Outstanding at Dec. 31, 2011	227,500,190					1,000	1,000			8,546,017	8,546,017			100	100
Net income	242					56				36				101
BALANCE at Sep. 30, 2012	4,453					968				803	26	576		1,618		755
Common Stock, Shares, Outstanding at Sep. 30, 2012	229,438,681					1,000	1,000			8,546,017	8,546,017			100	100
BALANCE at Mar. 31, 2012	4,366	2	3,340	(55)	1,079	873		347	526	804	26	576	202	1,526		705	821
Common Stock, Shares, Outstanding at Mar. 31, 2012		228,244,115					1,000				8,546,017				100
Net income	62				62	13			13	14			14	27			27
Other comprehensive income	4			4
Capital contribution from Parent														50		50
Dividends on common stock	(62)				(62)					(15)			(15)
Original issue shares, net	3		3
Original issue shares, net, shares		186,820
Shareholder DRP original shares, value	8		8
Shareholder DRP original shares, shares		420,880
Net activity related to stock-based awards	3		3
BALANCE at Jun. 30, 2012	4,384	2	3,354	(51)	1,079	886		347	539	803	26	576	201	1,603		755	848
Common Stock, Shares, Outstanding at Jun. 30, 2012		228,851,815					1,000				8,546,017				100
Net income	112				112	22			22	20			20	50			50
Other comprehensive income	4			4
Capital contribution from Parent						60		60
Dividends on common stock	(62)				(62)					(20)			(20)	(35)			(35)
Original issue shares, net	4		4
Original issue shares, net, shares		177,383
Shareholder DRP original shares, value	8		8
Shareholder DRP original shares, shares		409,483
Net activity related to stock-based awards	3		3
BALANCE at Sep. 30, 2012	$ 4,453	$ 2	$ 3,369	$ (47)	$ 1,129	$ 968		$ 407	$ 561	$ 803	$ 26	$ 576	$ 201	$ 1,618		$ 755	$ 863
Common Stock, Shares, Outstanding at Sep. 30, 2012	229,438,681	229,438,681				1,000	1,000			8,546,017	8,546,017			100	100