Segment Information - Segment Financial Information for Continuing Operations (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Goodwill	$ 1,407		$ 1,407		$ 1,407
Operating Revenue	1,117	1,051	2,447	2,231
Operating Expenses	966	906	2,123	1,953
Interest Expense	67	70	132	137
Interest and dividend income	1		1
Depreciation and amortization	132	116	265	228
Power Delivery [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Goodwill	1,400	1,400	1,400	1,400
Operating Revenue	1,040	1,006	2,312	2,130
Operating Expenses	881	866	1,984	1,867
Interest Expense	56	58	111	114
Depreciation and amortization	122	107	246	211
Interest benefit on uncertain tax positions				12
Pepco Energy Services [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenue	79	49	139	106
Operating Expenses	77	47	137	101
Depreciation and amortization	2	2	4	4
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating Revenue	(2)	(4)	(4)	(5)
Operating Expenses	8	(7)	2	(15)
Interest Expense	11	12	21	23
Interest and dividend income	1		1
Corporate and Other [Member] | Intersegment [Member]
Segment Reporting Information [Line Items]
Operating Revenue	(2)	(5)	(4)	(5)
Operating Expenses	(3)	(5)	(4)	(6)
Interest Expense	1			(4)
Interest and dividend income	(1)		(1)
Depreciation and amortization	8	7	15	13
Interest expense on uncertain tax positions				66
Valuation allowances against deferred tax assets				$ 101