Segment Information (Details) (USD $) In Millions	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010		Dec. 31, 2010
Operating Revenue	$ 1,643		$ 2,067		$ 4,686		$ 5,522
Operating Expenses	1,448		1,855		4,140		4,986
Operating Income	195		212		546		536
Interest Expense	64		68		189		240
Other Income (Expense)	7		6		27		17
Loss on Extinguishment of Debt			(135)				(135)
Income Tax Expense (Benefit) Related to Continuing Operations	55		(6)		143		52
Total Assets (excluding Assets Held For Sale)	14,570				14,570				14,480
Goodwill	1,407				1,407				1,407
Depreciation and amortization	115		104		325		286
Gain on early termination of finance leases held in trust					39
Gain on early termination of finance leases held in trust, after tax					3
Restructuring charge			14				14		30
Divestiture-related claims expense			9				11
State tax benefit							(14)
Write off of deferred tax asset related to Medicare Part D subsidy, ultimately offset against state tax benefits							(4)
Power Delivery [Member]
Operating Revenue	1,329		1,600		3,671		4,011
Operating Expenses	1,167	[1]	1,418	[2],[3],[4]	3,255	[5]	3,583	[4],[6],[7]
Operating Income	162		182		416		428
Interest Income	1				1		1
Interest Expense	53		51		155		155
Other Income (Expense)	7		6		23		15
Preferred Stock Dividends
Income Tax Expense (Benefit) Related to Continuing Operations	51		61		100	[8]	128	[9]
Net Income (Loss) from Continuing Operations	66		76		185		161
Total Assets (excluding Assets Held For Sale)	11,015		10,569		11,015		10,569
Construction Expenditures	239		181		603		526
Goodwill	1,400		1,400		1,400		1,400
Depreciation and amortization	107		97		301		264
Reversal of valuation allowances on tax deferred tax assets	22				22
Restructuring charge			13				13
Reversal of accrued interest income on uncertain, effectively settled tax positions							8
State tax benefit					14
Other Non-Regulated [Member]
Operating Revenue	7		15		35		41
Operating Expenses	2	[1]		[3],[4]	(34)	[10],[5]	3	[4],[7]
Operating Income	5		15		69		38
Interest Income					2		2
Interest Expense	3		2		10		9
Other Income (Expense)	(3)		(1)		(4)		(2)
Loss on Extinguishment of Debt
Preferred Stock Dividends	1		1		2		2
Income Tax Expense (Benefit) Related to Continuing Operations	(7)		2		25	[8]	8
Net Income (Loss) from Continuing Operations	5		9		30	[10]	19
Total Assets (excluding Assets Held For Sale)	1,467		1,524		1,467		1,524
Depreciation and amortization					1		1
Pepco Energy Services [Member]
Operating Revenue	312		457		993		1,480
Operating Expenses	300	[1]	442	[3],[4]	952	[5]	1,417	[4],[7]
Operating Income	12		15		41		63
Interest Income	1				1
Interest Expense	1		3		3		13
Other Income (Expense)	1				3		1
Loss on Extinguishment of Debt
Preferred Stock Dividends
Income Tax Expense (Benefit) Related to Continuing Operations	5		4		16	[8]	20
Net Income (Loss) from Continuing Operations	8		8		26		31
Total Assets (excluding Assets Held For Sale)	611		617		611		617
Construction Expenditures	4		2		11		3
Depreciation and amortization	4		5		13		14
Corporate And Other [Member]
Operating Revenue	(5)	[11]	(5)	[12]	(13)	[13]	(10)	[14]
Operating Expenses	(21)	[1],[11]	(5)	[12],[3],[4]	(33)	[13],[5]	(17)	[14],[4],[7]
Operating Income	16	[11]		[12]	20	[13]	7	[14]
Interest Income	(2)	[11]			(4)	[13]	(3)	[14]
Interest Expense	7	[11]	12	[12]	21	[13]	63	[14]
Other Income (Expense)	(1)	[11]	1	[12]	1	[13]	2	[14]
Loss on Extinguishment of Debt			135	[12]			135	[14]
Preferred Stock Dividends	(1)	[11]	(1)	[12]	(2)	[13]	(2)	[14]
Income Tax Expense (Benefit) Related to Continuing Operations	6	[11]	(73)	[12],[15]	2	[13],[8]	(104)	[14],[16]
Net Income (Loss) from Continuing Operations	1	[11]	(72)	[12]	(4)	[13]	(86)	[14]
Total Assets (excluding Assets Held For Sale)	1,475	[11],[13]	1,325	[12],[14]	1,475	[11],[13]	1,325	[12],[14]
Construction Expenditures	9	[11]	4	[12]	25	[13]	22	[14]
Depreciation and amortization	4		2		10		7
Restructuring charge			1				1
PHI Consolidated [Member]
Operating Revenue	1,643		2,067		4,686		5,522
Operating Expenses	1,448	[1]	1,855	[3],[4]	4,140	[5]	4,986	[4],[7]
Operating Income	195		212		546		536
Interest Expense	64		68		189		240
Other Income (Expense)	4		6		23		16
Loss on Extinguishment of Debt			135				135
Income Tax Expense (Benefit) Related to Continuing Operations	55		(6)		143	[8]	52
Net Income (Loss) from Continuing Operations	80		21		237		125
Total Assets (excluding Assets Held For Sale)	14,568		14,035		14,568		14,035
Construction Expenditures	252		187		639		551
Intersegment [Member]
Operating Revenue	(5)		(5)		(13)		(10)
Operating Expenses	(6)		(2)		(12)		(7)
Interest Income	(7)		(6)		(17)		(31)
Interest Expense	(6)		(5)		(15)		(30)
Preferred Stock Dividends			$ (1)		$ (2)		$ (2)

[1] Includes depreciation and amortization of $115 million, consisting of $107 million for Power Delivery, $4 million for Pepco Energy Services, and $4 million for Corporate and Other.

[2] Includes $9 million expense related to effects of Pepco divestiture-related claims.

[3] Includes depreciation and amortization of $104 million, consisting of $97 million for Power Delivery, $5 million for Pepco Energy Services and $2 million for Corporate and Other.

[4] Includes restructuring charge of $14 million, consisting of $13 million for Power Delivery and $1 million for Corporate and Other.

[5] Includes depreciation and amortization of $325 million, consisting of $301 million for Power Delivery, $13 million for Pepco Energy Services, $1 million for Other Non-Regulated, and $10 million for Corporate and Other.

[6] Includes $11 million expense related to effects of Pepco divestiture-related claims.

[7] Includes depreciation and amortization of $286 million, consisting of $264 million for Power Delivery, $14 million for Pepco Energy Services, $1 million for Other Non-Regulated and $7 million for Corporate and Other.

[8] Includes tax benefits of $14 million for Power Delivery primarily associated with an interest benefit related to federal tax liabilities and a $22 million reversal of previously recognized tax benefits for Other Non-Regulated associated with the early termination of cross-border energy leases held in trust.

[9] Includes $8 million reversal of accrued interest income on uncertain and effectively settled state income tax positions.

[10] Includes $39 million pre-tax ($3 million after-tax) gain from the early termination of cross-border energy leases held in trust.

[11] Total Assets in this column includes Pepco Holdings' goodwill balance of $1.4 billion, all of which is allocated to the Power Delivery segment for purposes of assessing impairment. Total assets also include capital expenditures related to certain hardware and software expenditures which primarily benefit the Power Delivery business. These expenditures are recorded as incurred in the Corporate and Other segment and are allocated to Power Delivery once the assets are placed in service. Additionally, Corporate and Other includes intercompany amounts of $(5) million for Operating Revenue, $(6) million for Operating Expense, $(7) million for Interest Income and $(6) million for Interest Expense.

[12] Total Assets in this column includes Pepco Holdings' goodwill balance of $1.4 billion, all of which is allocated to the Power Delivery segment for purposes of assessing impairment. Total assets also include capital expenditures related to certain hardware and software expenditures which primarily benefit the Power Delivery business. These expenditures are recorded as incurred in the Corporate and Other segment and are allocated to Power Delivery once the assets are placed in service. Additionally, Corporate and Other includes intercompany amounts of $(5) million for Operating Revenue, $(2) million for Operating Expense, $(6) million for Interest Income, $(5) million for Interest Expense, and $(1) million for Preferred Stock Dividends.

[13] Total Assets in this column includes Pepco Holdings' goodwill balance of $1.4 billion, all of which is allocated to the Power Delivery segment for purposes of assessing impairment. Total assets also include capital expenditures related to certain hardware and software expenditures which primarily benefit the Power Delivery business. These expenditures are recorded as incurred in the Corporate and Other segment and are allocated to Power Delivery once the assets are placed in service. Additionally, Corporate and Other includes intercompany amounts of $(13) million for Operating Revenue, $(12) million for Operating Expense, $(17) million for Interest Income, $(15) million for Interest Expense, and $(2) million for Preferred Stock Dividends.

[14] Total Assets in this column includes Pepco Holdings' goodwill balance of $1.4 billion, all of which is allocated to the Power Delivery segment for purposes of assessing impairment. Total assets also include capital expenditures related to certain hardware and software expenditures which primarily benefit the Power Delivery business. These expenditures are recorded as incurred in the Corporate and Other segment and are allocated to Power Delivery once the assets are placed in service. Additionally, Corporate and Other includes intercompany amounts of $(10) million for Operating Revenue, $(7) million for Operating Expense, $(31) million for Interest Income, $(30) million for Interest Expense, and $(2) million for Preferred Stock Dividends.

[15] Includes current state tax benefits resulting from the restructuring of certain Pepco Holdings subsidiaries which have subjected Pepco Holdings to state income taxes in new jurisdictions.

[16] Includes $14 million of state tax benefits resulting from the restructuring of certain Pepco Holdings subsidiaries, partially offset by a charge of $4 million to write off deferred tax assets related to the Medicare Part D subsidy.