Quarterly Financial Information - Schedule of Quarterly Financial Information (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information [Line Items]
Intra company revenue	$ 1,091	$ 1,344	$ 1,051	$ 1,180	$ 1,056	$ 1,389	$ 1,057	$ 1,123	$ 4,666	$ 4,625	$ 4,964
Change in estimates and interest related to uncertain and effectively settled tax positions				56					56	(8)	(5)
Establishment of valuation allowances related to deferred tax assets				101					101
Potomac Electric Power Co [Member]
Quarterly Financial Information [Line Items]
Change in estimates and interest related to uncertain and effectively settled tax positions				5					(3)	(11)	(9)
Establishment of valuation allowances related to deferred tax assets									0	0
Tax benefits related to uncertain tax position IRS								10
Pepco Energy Services [Member]
Quarterly Financial Information [Line Items]
Impairment losses, pre-tax	4									12
Impairment losses, after-tax	3									7
Pepco Energy Services [Member] | Intra Segment [Member]
Quarterly Financial Information [Line Items]
Intra company revenue										$ 9