Consolidated Statements Of Equity (USD $) In Millions, except Share data	Total USD ($)	Common Stock [Member] USD ($)	Premium On Stock [Member] USD ($)	Retained Earnings [Member] USD ($)	Accumulated Other Comprehensive (Loss) Income [Member] USD ($)	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, 2009	$ 4,256	$ 2	$ 3,227	$ 1,268	$ (241)	$ 808		$ 336	$ 472	$ 642	$ 26	$ 473	$ 143	$ 1,435		$ 705	$ 730
Common Stock, Shares, Outstanding, Beginning Balance at Dec. 31, 2009		222,269,895					1,000				8,546,017				100
Net income	32			32		45			45	53			53	108			108
Other comprehensive income	135				135
Dividends on common stock	(241)			(241)		(23)			(23)	(35)			(35)	(115)			(115)
Original issue shares, net	16		16
Capital contribution from Parent						11		11		43		43
Original issue shares, net, shares		1,041,482
Shareholder DRP original shares, value	31		31
Shareholder DRP original shares, shares	2,000,000	1,770,875
Net activity related to stock-based awards	1		1
BALANCE at Dec. 31, 2010	4,230	2	3,275	1,059	(106)	841		347	494	703	26	516	161	1,428		705	723
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2010		225,082,252					1,000				8,546,017				100
Net income	64					23				6				18
BALANCE at Mar. 31, 2011
BALANCE at Dec. 31, 2010	4,230	2	3,275	1,059	(106)	841			494	703	26	516	161	1,428		705	723
Common Stock, Shares, Outstanding, Beginning Balance at Dec. 31, 2010		225,082,252					1,000				8,546,017				100
Net income	257			257		71			71	39			39	99			99
Other comprehensive income	43				43
Dividends on common stock	(244)			(244)		(60)			(60)					(25)			(25)
Original issue shares, net	17		17
Capital contribution from Parent										60		60
Original issue shares, net, shares		854,124
Shareholder DRP original shares, value	30		30
Shareholder DRP original shares, shares	2,000,000	1,563,814
Net activity related to stock-based awards	3		3
BALANCE at Dec. 31, 2011	4,336	2	3,325	1,072	(63)	852			505	802	26	576	200	1,502			797
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2011	227,500,190	227,500,190				1,000	1,000			8,546,017	8,546,017			100	100
BALANCE at Sep. 30, 2011
Net income	19					15				(2)				11
BALANCE at Dec. 31, 2011	4,336					852				802	26			1,502
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2011	227,500,190					1,000	1,000			8,546,017	8,546,017			100	100
Net income	68					21				2				24
BALANCE at Mar. 31, 2012
BALANCE at Dec. 31, 2011	4,336	2	3,325	1,072	(63)	852		347	505	802	26		200	1,502		705	797
Common Stock, Shares, Outstanding, Beginning Balance at Dec. 31, 2011	227,500,190	227,500,190				1,000	1,000			8,546,017	8,546,017			100	100
Net income	285			285		73			73	35			35	126			126
Other comprehensive income	15				15
Dividends on common stock	(248)			(248)						(35)			(35)	(35)			(35)
Original issue shares, net	19		19
Capital contribution from Parent						60		60						50		50
Original issue shares, net, shares		854,060
Shareholder DRP original shares, value	32		32
Shareholder DRP original shares, shares	2,000,000	1,661,177
Net activity related to stock-based awards	7		7
BALANCE at Dec. 31, 2012	4,446	2	3,383	1,109	(48)	985		407	578	802	26	576	200	1,643		755	888
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2012	230,015,427	230,015,427				1,000	1,000			8,546,017	8,546,017			100	100
BALANCE at Sep. 30, 2012
Net income	43					17				(1)				25
BALANCE at Dec. 31, 2012	$ 4,446					$ 985				$ 802	$ 26	$ 576		$ 1,643
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2012	230,015,427					1,000	1,000			8,546,017	8,546,017			100	100