Document And Entity Information	9 Months Ended
	Sep. 30, 2011	Oct. 31, 2011
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q3
Entity Registrant Name	PEPCO HOLDINGS INC
Entity Central Index Key	0001135971
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Pepco Holdings Inc [Member]
Trading Symbol	POM
Entity Common Stock, Shares Outstanding		226,956,398
Potomac Electric Power Co [Member]
Entity Registrant Name	POTOMAC ELECTRIC POWER CO
Entity Central Index Key	0000079732
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		100
Delmarva Power & Light Co/De [Member]
Entity Registrant Name	DELMARVA POWER & LIGHT CO /DE/
Entity Central Index Key	0000027879
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		1,000
Atlantic City Electric Co [Member]
Entity Registrant Name	ATLANTIC CITY ELECTRIC CO
Entity Central Index Key	0000008192
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		8,546,017