Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended														12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011	Jun. 30, 2011		Mar. 31, 2011	Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Segment Reporting Information [Line Items]
Operating Revenue	$ 1,234		$ 1,643	$ 1,409		$ 1,634	$ 1,517		$ 2,067		$ 1,636		$ 1,819		$ 5,920		$ 7,039		$ 7,402
Operating Expenses	1,143		1,448	1,207	[1]	1,485	1,429	[2],[3]	1,855	[2],[3]	1,443	[2],[3]	1,688	[2],[3]	5,283		6,415	[2],[3]	6,754
Operating Income	91		195	202		149	88		212		193		131		637		624		648
Interest Expense															254		306		340
Impairment losses																			(4)
Other Income (Expense)															33		22		16
Loss on Extinguishment of Debt							(54)		(135)								(189)
Loss on Extinguishment of Debt, Net																	104
Losses on treasury rate locks reclassified into income															1		18		5
Losses on treasury rate locks reclassified into income, net																	9
Income Tax Expense (Benefit)							15								28		21		12
Total Assets (excluding Assets Held For Sale)	14,910						14,480								14,910		14,480
Goodwill	1,407						1,407								1,407		1,407		1,407
Depreciation and amortization															426		393		349
Gain on early termination of finance leases held in trust				39											39
Gain on early termination of finance leases held in trust, after tax															3
Restructuring charge							16		14								30
Divestiture-related claims expense									9		2						11		(40)
Divestiture-related claims expense, net																			24
Reversal of accrued interest income on uncertain, effectively settled tax positions																	12
Federal tax liabilites				(14)
Write off of deferred tax asset related to Medicare Part D subsidy, ultimately offset against state tax benefits																	3
Power Delivery [Member]
Segment Reporting Information [Line Items]
Operating Revenue															4,650		5,114		4,980
Operating Expenses															4,150	[4]	4,611	[5],[6],[7]	4,475	[8],[9]
Operating Income															500		503		505
Interest Income															1		2		3
Interest Expense															208		207		211
Other Income (Expense)															29		20		11
Income Tax Expense (Benefit)															112	[10]	112	[11]	109
Net Income (Loss) from Continuing Operations															210		206		199	[12]
Total Assets (excluding Assets Held For Sale)	11,008						10,621								11,008		10,621		10,239
Construction Expenditures															888		765		622
Goodwill	1,400						1,400								1,400		1,400		1,400
Depreciation and amortization															394		357		323
Restructuring charge																	29
Divestiture-related claims expense																			40
State tax benefit																			11
Federal tax liabilites															14
Other Non-Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenue															48		54		51
Operating Expenses															(30)	[1],[4]	6	[5],[6]	4	[8]
Operating Income															78		48		47
Interest Income															4		3		4
Interest Expense															13		12		14
Other Income (Expense)															(4)		(2)		2
Loss on Extinguishment of Debt
Preferred Stock Dividends															3		3		3
Income Tax Expense (Benefit)															27	[10]	9		5
Net Income (Loss) from Continuing Operations															35	[1]	25		31
Total Assets (excluding Assets Held For Sale)	1,499						1,537								1,499		1,537		1,515
Depreciation and amortization															2		1		2
Reversal of valuation allowances on tax deferred tax assets	22														22
Pepco Energy Services [Member]
Segment Reporting Information [Line Items]
Operating Revenue															1,238		1,883		2,383
Operating Expenses															1,206	[4]	1,812	[5],[6]	2,294	[8]
Operating Income															32		71		89
Interest Income															1		1		1
Interest Expense															3		16		30
Other Income (Expense)															3		2		3
Loss on Extinguishment of Debt
Income Tax Expense (Benefit)															9	[10]	22		23
Net Income (Loss) from Continuing Operations															24		36		40
Total Assets (excluding Assets Held For Sale)	565						623								565		623		734
Construction Expenditures															14		7		12
Depreciation and amortization															17		24		18
Corporate And Other [Member]
Segment Reporting Information [Line Items]
Operating Revenue															(16)	[13]	(12)	[14]	(12)	[15]
Operating Expenses															(43)	[13],[4]	(14)	[14],[5],[6]	(19)	[15],[8]
Operating Income															27	[13]	2	[14]	7	[15]
Interest Income															(5)	[13]	(6)	[14]	(6)	[15]
Interest Expense															30	[13]	71	[14]	85	[15]
Impairment losses															(5)	[13]
Other Income (Expense)															2	[13]	1	[14]	1	[15]
Loss on Extinguishment of Debt																	(189)	[14],[16]
Losses on treasury rate locks reclassified into income																	15
Preferred Stock Dividends															(3)	[13]	(3)	[14]	(3)	[15]
Income Tax Expense (Benefit)															1	[10],[13]	(132)	[14],[17]	(33)	[15]
Net Income (Loss) from Continuing Operations															(9)	[13]	(128)	[14]	(47)	[15]
Total Assets (excluding Assets Held For Sale)	1,838	[13]					1,582	[14]							1,838	[13]	1,582	[14]	1,294	[15]
Construction Expenditures															39	[13]	30	[14]	30	[15]
Depreciation and amortization															13		11		6
Restructuring charge																	1
PHI Consolidated [Member]
Segment Reporting Information [Line Items]
Operating Revenue															5,920		7,039		7,402
Operating Expenses															5,283	[4]	6,415	[5],[6]	6,754	[8]
Operating Income															637		624		648
Interest Income															1				2
Interest Expense															254		306		340
Impairment losses															(5)
Other Income (Expense)															30		21		17
Loss on Extinguishment of Debt																	(189)
Income Tax Expense (Benefit)															149	[10]	11		104
Net Income (Loss) from Continuing Operations															260		139		223
Total Assets (excluding Assets Held For Sale)	14,910						14,363								14,910		14,363		13,782
Construction Expenditures															941		802		664
Subsidiaries [Member]
Segment Reporting Information [Line Items]
State tax benefit																	(14)
Intersegment [Member]
Segment Reporting Information [Line Items]
Operating Revenue															(16)		(12)		(12)
Operating Expenses															(15)		(10)		(4)
Interest Income															(22)		(36)		(76)
Interest Expense															(22)		(36)		(73)
Preferred Stock Dividends															(3)		(3)		(3)
State income tax benefits associated with loss on extinguishment of debt																	$ 17

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

[2] Includes restructuring charges of $14 million and $16 million in the third and fourth quarters, respectively.

[3] Includes expenses of $2 million and $9 million in the second and third quarters, respectively, related to the effects of Pepco divestiture-related claims.

[4] Includes depreciation and amortization expense of $426 million, consisting of $394 million for Power Delivery, $17 million for Pepco Energy Services, $2 million for Other Non-Regulated, and $13 million for Corporate and Other.

[5] Includes depreciation and amortization expense of $393 million, consisting of $357 million for Power Delivery, $24 million for Pepco Energy Services, $1 million for Other Non-Regulated, and $11 million for Corporate and Other.

[6] Includes restructuring charge of $30 million, consisting of $29 million for Power Delivery and $1 million for Corporate and Other.

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

[8] Includes depreciation and amortization expense of $349 million, consisting of $323 million for Power Delivery, $18 million for Pepco Energy Services, $2 million for Other Non-Regulated, and $6 million for Corporate and Other.

[9] Includes $40 million ($24 million after-tax) gain related to effects of Pepco divestiture-related claims.

[10] 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.

[11] Includes $12 million of net Federal and state income tax benefits primarily related to adjustments of accrued interest on uncertain and effectively settled tax positions.

[12] Includes $11 million after-tax state income tax benefit, net of fees, related to a change in the tax reporting for the disposition of certain assets in prior years.

[13] Total Assets in this column includes Pepco Holdings' goodwill balance of $1.4 billion, all of which is allocated to Power Delivery for purposes of assessing impairment. Total assets also include capital expenditures related to certain hardware and software expenditures which primarily benefit Power Delivery. 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. Corporate and Other includes intercompany amounts of $(16) million for Operating Revenue, $(15) million for Operating Expense, $(22) million for Interest Income, $(22) million for Interest Expense, and $(3) 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 Power Delivery for purposes of assessing impairment. Total assets also include capital expenditures related to certain hardware and software expenditures which primarily benefit Power Delivery. 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. Corporate and Other includes intercompany amounts of $(12) million for Operating Revenue, $(10) million for Operating Expense, $(36) million for Interest Income, $(36) million for Interest Expense, and $(3) million for Preferred Stock Dividends.

[15] Total Assets in this column includes Pepco Holdings' goodwill balance of $1.4 billion, all of which is allocated to Power Delivery for purposes of assessing impairment. Total assets also include capital expenditures related to certain hardware and software expenditures which primarily benefit Power Delivery. 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. Corporate and Other includes intercompany amounts of $(12) million for Operating Revenue, $(4) million for Operating Expense, $(76) million for Interest Income, $(73) million for Interest Expense, and $(3) million for Preferred Stock Dividends.

[16] Includes $174 million ($104 million after-tax) related to loss on extinguishment of debt and $15 million ($9 million after-tax) related to the reclassification of treasury rate lock losses from AOCL to income related to cash tender offers for debt made in 2010.

[17] Includes $14 million of state tax benefits resulting from the restructuring of certain PHI subsidiaries and $17 million of state income tax benefits associated with the loss on extinguishment of debt, partially offset by a charge of $3 million to write off deferred tax assets related to the subsidy pursuant to the prescription drug benefit (Medicare Part D) under the Medicare Prescription Drug Improvement and Modernization Act of 2003 (the Medicare Act).