Segment Information (Segment Financial Information For Continuing Operations) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012
Segment Reporting Information [Line Items]
Operating Revenue	$ 852		$ 1,242
Operating Expenses	1,088		1,111
Operating (Loss) Income	(236)		131
Interest Expense	67		65
Total Assets (excluding Assets Held For Sale)	15,655				15,788
Goodwill	1,407				1,407
Non-cash pre-tax charge	373
Depreciation and amortization	112		110
Interest expense on uncertain tax positions	16
Income tax benefit related to uncertain and effectively settled tax positions			10
Power Delivery [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,124		1,055
Operating Expenses	1,001	[1]	954	[2]
Operating (Loss) Income	123		101
Interest Expense	56		53
Other Income (Expenses)	6		8
Income Tax Expense (Benefit)	15	[3]	9	[4]
Net Income (Loss) from Continuing Operations	58		47
Total Assets (excluding Assets Held For Sale)	12,453		11,473
Construction Expenditures	282		280
Goodwill	1,400		1,400
Depreciation and amortization	104		99
Interest benefit	12
Intersegment [Member]
Segment Reporting Information [Line Items]
Operating Revenue	(1)		(4)
Operating Expenses	(1)		(6)
Interest Income	(3)		(5)
Interest Expense	(4)		(5)
Preferred Stock Dividends	(1)		(1)
Pepco Energy Services [Member]
Segment Reporting Information [Line Items]
Operating Revenue	97		178
Operating Expenses	94	[1]	169	[2]
Operating (Loss) Income	3		9
Interest Expense			1
Other Income (Expenses)	1
Income Tax Expense (Benefit)	1	[3]	3
Net Income (Loss) from Continuing Operations	3		5
Total Assets (excluding Assets Held For Sale)	368		583
Construction Expenditures	1		5
Depreciation and amortization	2		6
Other Non-Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenue	(368)	[5]	13
Operating Expenses			1	[2]
Operating (Loss) Income	(368)		12
Interest Income	1		1
Interest Expense	1		3
Other Income (Expenses)	1		1
Preferred Stock Dividends	1		1
Income Tax Expense (Benefit)	53	[3],[6]
Net Income (Loss) from Continuing Operations	(421)		10
Total Assets (excluding Assets Held For Sale)	882		1,487
Depreciation and amortization			1
Interest expense on uncertain tax positions	16
Non cash charges for tax consequences	64
Valuation allowance against deferred tax assets	101
Corporate And Other [Member]
Segment Reporting Information [Line Items]
Operating Revenue	(1)	[7]	(4)	[8]
Operating Expenses	(7)	[1],[7]	(13)	[2],[8]
Operating (Loss) Income	6	[7]	9	[8]
Interest Income	(1)	[7]	(1)	[8]
Interest Expense	10	[7]	8	[8]
Other Income (Expenses)			(1)	[8]
Preferred Stock Dividends	(1)	[7]	(1)	[8]
Income Tax Expense (Benefit)	66	[3],[7]	(1)	[8]
Net Income (Loss) from Continuing Operations	(70)	[7]	1	[8]
Total Assets (excluding Assets Held For Sale)	1,952	[7]	1,684	[8]
Construction Expenditures	13	[7]	6	[8]
Depreciation and amortization	6		4
Interest expense on uncertain tax positions	66
PHI Consolidated [Member]
Segment Reporting Information [Line Items]
Operating Revenue	852		1,242
Operating Expenses	1,088	[1]	1,111	[2]
Operating (Loss) Income	(236)		131
Interest Expense	67		65
Other Income (Expenses)	8		8
Income Tax Expense (Benefit)	135	[3]	11
Net Income (Loss) from Continuing Operations	(430)		63
Total Assets (excluding Assets Held For Sale)	15,655		15,227
Construction Expenditures	$ 296		$ 291

[1] Includes depreciation and amortization expense of $112 million, consisting of $104 million for Power Delivery, $2 million for Pepco Energy Services and $6 million for Corporate and Other.

[2] Includes depreciation and amortization expense of $110 million, consisting of $99 million for Power Delivery, $6 million for Pepco Energy Services, $1 million for Other Non-Regulated and $4 million for Corporate and Other.

[3] Includes after-tax interest associated with uncertain and effectively settled tax positions allocated to each member of the consolidated group, including a $12 million interest benefit for Power Delivery and interest expense of $16 million and $66 million for Other Non-Regulated and Corporate and Other, respectively

[4] Includes income tax benefits of $10 million related to uncertain and effectively settled tax positions, primarily due to the effective settlement with the Internal Revenue Service with respect to the methodology used historically to calculate deductible mixed service costs and the expiration of the statute of limitations associated with an uncertain tax position at Pepco.

[5] Includes a non-cash pre-tax charge of $373 million to reduce the carrying value of the cross-border energy lease investments.

[6] Includes non-cash charges of $64 million primarily for the tax consequences associated with PHI's change in intent regarding foreign investment opportunities associated with the cross-border energy lease investments and $101 million representing the establishment of valuation allowances against certain deferred tax assets of PCI included in Other Non-Regulated.

[7] 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 $(1) million for Operating Revenue, $(1) million for Operating Expenses, $(3) million for Interest Income, $(4) million for Interest Expense and $(1) million for Preferred Stock Dividends.

[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, $(6) million for Operating Expenses, $(5) million for Interest Income, $(5) million for Interest Expense and $(1) million for Preferred Stock Dividends.