Document And Entity Information (USD $)	12 Months Ended			12 Months Ended		12 Months Ended		12 Months Ended
	Dec. 31, 2011	Jun. 30, 2011	Feb. 15, 2012 Pepco Holdings Inc [Member]	Dec. 31, 2011 Potomac Electric Power Co [Member]	Feb. 15, 2012 Potomac Electric Power Co [Member]	Dec. 31, 2011 Delmarva Power & Light Co/De [Member]	Feb. 15, 2012 Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 Atlantic City Electric Co [Member]	Feb. 15, 2012 Atlantic City Electric Co [Member]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Trading Symbol	POM
Entity Registrant Name	PEPCO HOLDINGS INC			POTOMAC ELECTRIC POWER CO		DELMARVA POWER & LIGHT CO /DE/		ATLANTIC CITY ELECTRIC CO
Entity Central Index Key	0001135971			0000079732		0000027879		0000008192
Current Fiscal Year End Date	--12-31			--12-31		--12-31		--12-31
Entity Filer Category	Large Accelerated Filer			Non-accelerated Filer		Non-accelerated Filer		Non-accelerated Filer
Entity Well-known Seasoned Issuer	Yes			No		No		No
Entity Voluntary Filers	No			No		No		No
Entity Current Reporting Status	Yes			Yes		Yes		Yes
Entity Public Float		$ 4,432,800,000
Entity Common Stock, Shares Outstanding			227,609,131		100		1,000		8,546,017