Consolidated Statements Of Equity (USD $) In Millions, except Share data, unless otherwise specified	Common Stock [Member] Potomac Electric Power Co [Member]	Common Stock [Member] Delmarva Power & Light Co/De [Member]	Common Stock [Member] Atlantic City Electric Co [Member] USD ($)	Common Stock [Member] USD ($)	Premium On Stock [Member] Potomac Electric Power Co [Member] USD ($)	Premium On Stock [Member] Delmarva Power & Light Co/De [Member] USD ($)	Premium On Stock [Member] Atlantic City Electric Co [Member] USD ($)	Premium On Stock [Member] USD ($)	Accumulated Other Comprehensive (Loss) Income [Member] USD ($)	Retained Earnings [Member] Potomac Electric Power Co [Member] USD ($)	Retained Earnings [Member] Delmarva Power & Light Co/De [Member] USD ($)	Retained Earnings [Member] Atlantic City Electric Co [Member] USD ($)	Retained Earnings [Member] USD ($)	Potomac Electric Power Co [Member] USD ($)	Delmarva Power & Light Co/De [Member] USD ($)	Atlantic City Electric Co [Member] USD ($)	Total USD ($)
BALANCE at Dec. 31, 2008			$ 26	$ 2	$ 611	$ 304	$ 344	$ 3,179	$ (262)	$ 624	$ 448	$ 166	$ 1,271	$ 1,235	$ 752	$ 536	$ 4,190
Common Stock, Shares, Outstanding, Beginning Balance at Dec. 31, 2008	100	1,000	8,546,017	218,906,220
Net Income										106	52	41	235	106	52	41	235
Other comprehensive (loss) income									21								21
Dividends on common stock											(28)	(64)	(238)		(28)	(64)	(238)
Capital contribution from parent					94	32	129							94	32	129
Issuance of common stock
Original issue shares, net								18									18
Original issue shares, net, shares				1,210,261
Shareholder DRP original shares								31									31
Shareholder DRP original shares (in shares)				2,153,414													2,000,000
Net activity related to stock-based awards								(1)									(1)
BALANCE at Dec. 31, 2009			26	2	705	336	473	3,227	(241)	730	472	143	1,268	1,435	808	642	4,256
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2009	100	1,000	8,546,017	222,269,895
Net Income										108	45	53	32	108	45	53	32
Other comprehensive (loss) income									135								135
Dividends on common stock										(115)	(23)	(35)	(241)	(115)	(23)	(35)	(241)
Capital contribution from parent						11	43								11	43
Issuance of common stock
Original issue shares, net								16									16
Original issue shares, net, shares				1,041,482
Shareholder DRP original shares								31									31
Shareholder DRP original shares (in shares)				1,770,875													2,000,000
Net activity related to stock-based awards								1									1
BALANCE at Dec. 31, 2010			26	2	705	347	516	3,275	(106)	723	494	161	1,059	1,428	841	703	4,230
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2010	100	1,000	8,546,017	225,082,252										100	1,000	8,546,017	225,082,252
Net Income										99	71	39	257	99	71	39	257
Other comprehensive (loss) income									43								43
Dividends on common stock										(25)	(60)		(244)	(25)	(60)		(244)
Capital contribution from parent							60									60
Issuance of common stock
Original issue shares, net								17									17
Original issue shares, net, shares				854,124
Shareholder DRP original shares								30									30
Shareholder DRP original shares (in shares)				1,563,814													2,000,000
Net activity related to stock-based awards								3									3
BALANCE at Dec. 31, 2011			$ 26	$ 2	$ 705	$ 347	$ 576	$ 3,325	$ (63)	$ 797	$ 505	$ 200	$ 1,072	$ 1,502	$ 852	$ 802	$ 4,336
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2011	100	1,000	8,546,017	227,500,190										100	1,000	8,546,017	227,500,190