Segment Information - Segment Financial Information for Continuing Operations (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Goodwill	$ 1,407		$ 1,407
Operating Revenue	1,330	1,180
Operating Expenses	1,157	1,047
Interest expense	65	67
Depreciation and amortization	133	112
Power Delivery [Member]
Segment Reporting Information [Line Items]
Goodwill	1,400	1,400
Depreciation and amortization	124	104
Interest benefit		12
Pepco Energy Services [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	2	2
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	7	6
Interest expense on uncertain tax positions		66
Valuation allowance against deferred tax assets		101
Corporate and Other [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Operating Revenue	(2)	0
Operating Expenses	(1)	(1)
Interest expense	$ (1)	$ (4)