Segment Information - Segment Financial Information for Continuing Operations (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
Segment Reporting Information [Line Items]
Operating Revenue	$ 1,091	$ 1,344	$ 1,051	$ 1,180	$ 1,056	$ 1,389	$ 1,057	$ 1,123	$ 4,666	$ 4,625	$ 4,964
Operating Expenses	936	1,109	906	1,047	954	1,188	932	1,010	3,998	4,084	4,411
Operating Income (Loss)	155	235	145	133	102	201	125	113	668	541	553
Interest expense									273	256	242
Impairment Losses									(4)	(12)
Income Tax Expense (Benefit)	39	65	30	185	11	57	26	9	319	103	114
Total Assets (excluding Assets Held for Disposition)	14,848				15,794				14,848	15,794
Pepco Energy Services [Member]
Segment Reporting Information [Line Items]
Impairment Losses									(4)	(12)
Operating Segments [Member] | Power Delivery [Member]
Segment Reporting Information [Line Items]
Operating Revenue									4,472	4,378	4,650
Operating Expenses									3,828	3,847	4,150
Operating Income (Loss)									644	531	500
Interest Income										1	1
Interest expense									228	219	208
Other Income (Expenses)									28	32	29
Income Tax Expense (Benefit)									155	110	112
Net Income (Loss) from Continuing Operations									289	235	210
Total Assets (excluding Assets Held for Disposition)	13,027				12,149				13,027	12,149	11,008
Construction Expenditures									1,194	1,168	888
Operating Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating Revenue									(9)	(9)	(16)
Operating Expenses									(31)	(34)	(40)
Operating Income (Loss)									22	25	24
Interest Income										(1)	(1)
Interest expense									44	35	32
Impairment Losses										(1)	(5)
Other Income (Expenses)									3	3	(2)
Income Tax Expense (Benefit)									163		(6)
Net Income (Loss) from Continuing Operations									(182)	(9)	(10)
Total Assets (excluding Assets Held for Disposition)	1,485				2,028				1,485	2,028	1,988
Construction Expenditures									112	37	39
Operating Segments [Member] | Pepco Energy Services [Member]
Segment Reporting Information [Line Items]
Operating Revenue									203	256	330
Operating Expenses									201	271	301
Operating Income (Loss)									2	(15)	29
Interest Income										1	1
Interest expense									1	2	2
Other Income (Expenses)									3	1	2
Income Tax Expense (Benefit)									1	(7)	8
Net Income (Loss) from Continuing Operations									3	(8)	22
Total Assets (excluding Assets Held for Disposition)	335				342				335	342	529
Construction Expenditures									4	11	14
Operating Segments [Member] | PHI Consolidated [Member]
Segment Reporting Information [Line Items]
Operating Revenue									4,666	4,625	4,964
Operating Expenses									3,998	4,084	4,411
Operating Income (Loss)									668	541	553
Interest Income										1	1
Interest expense									273	256	242
Impairment Losses										(1)	(5)
Other Income (Expenses)									34	36	29
Income Tax Expense (Benefit)									319	103	114
Net Income (Loss) from Continuing Operations									110	218	222
Total Assets (excluding Assets Held for Disposition)	14,847				14,519				14,847	14,519	13,525
Construction Expenditures									$ 1,310	$ 1,216	$ 941