Organization - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		3 Months Ended			12 Months Ended
	Dec. 31, 2013	Mar. 31, 2013	Sep. 30, 2013 Pepco Energy Services [Member]	Jun. 30, 2013 Discontinued Operations [Member]	Mar. 31, 2013 Discontinued Operations [Member]	Dec. 31, 2013 Discontinued Operations [Member]	Dec. 31, 2011 Discontinued Operations [Member]	Dec. 31, 2013 Discontinued Operations [Member] PHI [Member]	Dec. 31, 2013 Discontinued Operations [Member] Power Delivery [Member]	Dec. 31, 2013 Discontinued Operations [Member] Corporate and Other [Member]	Dec. 31, 2013 Discontinued Operations [Member] Interest Expense [Member]	Dec. 31, 2013 Discontinued Operations [Member] Potomac Capital Investment Corporation (PCI) [Member] PHI [Member]
Reorganization [Line Items]
Asset retirement obligation			$ 2
Establishment of valuation allowance on deferred tax assets		101
PCI Recorded Deferred Tax Asset In Prior years		101
Deferred tax assets valuation allowance charged off	101
After-tax non-cash charges				6	323
Other non-cash charge						373	7
After-tax effect of revised lease rerun						313
After-tax non-cash charge								70			16
Interest benefit									12
Interest expense on uncertain tax positions										$ 66		$ 16