Segment Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011		Dec. 31, 2011
Segment Reporting Information [Line Items]
Operating Revenue	$ 1,179		$ 1,412		$ 2,471		$ 3,050
Operating Expenses	1,027	[1]	1,210	[2]	2,180	[3]	2,699	[4]
Operating Income	152		202		291		351
Interest Expense	65		63		130		125
Other Income (Expenses)	10		10		18		19
Income Tax Expense (Benefit)	35		54	[5]	49		88	[5]
Net Income (Loss) from Continuing Operations	62		95		130		157
Total Assets (excluding Assets Held For Sale)	15,421		14,233		15,421		14,233		14,910
Construction Expenditures	298		216		589		387
Goodwill	1,407				1,407				1,407
Depreciation and amortization	111		105
Impairment losses	3				3
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
Federal tax liabilities			14
Reversal of previously recognized tax benefits			22				22
Power Delivery [Member]
Segment Reporting Information [Line Items]
Operating Revenue	984		1,093		2,039		2,342
Operating Expenses	860	[1]	957	[2]	1,814	[3]	2,088	[4]
Operating Income	124		136		225		254
Interest Expense	53		52		106		102
Other Income (Expenses)	8		8		16		16
Income Tax Expense (Benefit)	25		20	[5]	34		49	[5]
Net Income (Loss) from Continuing Operations	54		72		101		119
Total Assets (excluding Assets Held For Sale)	11,734		10,803		11,734		10,803
Construction Expenditures	285		204		565		364
Goodwill	1,407		1,400		1,407		1,400
Depreciation and amortization	100		97
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Expenses	(1)		(4)
Interest Income	(6)		(5)
Interest Expense	(5)		(5)
Operating Revenue	(4)		(6)
Pepco Energy Services [Member]
Segment Reporting Information [Line Items]
Operating Revenue	185		311		413		688
Operating Expenses	171	[1],[6]	298	[2]	382	[3],[7]	659	[4]
Operating Income	14		13		31		29
Interest Expense			1		1		2
Other Income (Expenses)			1				2
Income Tax Expense (Benefit)	6		5	[5]	12		11	[5]
Net Income (Loss) from Continuing Operations	8		8		18		18
Total Assets (excluding Assets Held For Sale)	536		615		536		615
Construction Expenditures	5		6		10		7
Depreciation and amortization	4		5
Other Non-Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenue	14		14		27		28
Operating Expenses	2	[1]	(38)	[2],[6]	3	[3]	(36)	[4],[6]
Operating Income	12		52		24		64
Interest Income	1		1		2		2
Interest Expense	4		4		7		7
Other Income (Expenses)					1		(1)
Income Tax Expense (Benefit)	2		30	[5]	2		32	[5]
Net Income (Loss) from Continuing Operations	7		19	[6]	17		25	[6]
Total Assets (excluding Assets Held For Sale)	1,499		1,461		1,499		1,461
Depreciation and amortization			1
Preferred Stock Dividends					1		1
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating Revenue	(4)	[8]	(6)	[9]	(8)	[10]	(8)	[11]
Operating Expenses	(6)	[1],[8]	(7)	[2],[9]	(19)	[10],[3]	(12)	[11],[4]
Operating Income	2	[8]	1	[9]	11	[10]	4	[11]
Interest Income	(1)	[8]	(1)	[9]	(2)	[10]	(2)	[11]
Interest Expense	8	[8]	6	[9]	16	[10]	14	[11]
Other Income (Expenses)	2	[8]	1	[9]	1	[10]	2	[11]
Income Tax Expense (Benefit)	2	[8]	(1)	[5],[9]	1	[10]	(4)	[11],[5]
Net Income (Loss) from Continuing Operations	(7)	[8]	(4)	[9]	(6)	[10]	(5)	[11]
Total Assets (excluding Assets Held For Sale)	1,652	[10],[8]	1,354	[11],[9]	1,652	[10],[8]	1,354	[11],[9]
Construction Expenditures	8	[8]	6	[9]	14	[10]	16	[11]
Depreciation and amortization	7		2
Preferred Stock Dividends					$ (1)	[10]	$ (1)	[11]

[1] Includes depreciation and amortization expense of $111 million, consisting of $100 million for Power Delivery, $4 million for Pepco Energy Services and $7 million for Corporate and Other.

[2] Includes depreciation and amortization expense of $105 million, consisting of $97 million for Power Delivery, $5 million for Pepco Energy Services, $1 million for Other Non-Regulated and $2 million for Corporate and Other.

[3] Includes depreciation and amortization expense of $221 million, consisting of $199 million for Power Delivery, $10 million for Pepco Energy Services, $1 million for Other Non-Regulated and $11 million for Corporate and Other.

[4] Includes depreciation and amortization expense of $210 million, consisting of $194 million for Power Delivery, $9 million for Pepco Energy Services, $1 million for Other Non-Regulated and $6 million for Corporate and Other.

[5] 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 finance leases held in trust.

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

[7] Includes impairment losses of $3 million associated primarily with Pepco Energy Services' investment in a landfill gas-fired electric generation facility.

[8] 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 $(4) million for Operating Revenue, $(1) million for Operating Expenses, $(6) million for Interest Income and $(5) million for Interest Expense.

[9] 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 $(6) million for Operating Revenue, $(4) million for Operating Expenses, $(5) million for Interest Income and $(5) million for Interest Expense.

[10] 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 $(8) million for Operating Revenue, $(7) million for Operating Expenses, $(11) million for Interest Income, $(10) million for Interest Expense and $(1) million for Preferred Stock Dividends.

[11] 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 $(8) million for Operating Revenue, $(6) million for Operating Expenses, $(10) million for Interest Income, $(9) million for Interest Expense and $(1) million for Preferred Stock Dividends.