Discontinued Operations (Fair Value Of Derivative Instruments By Balance Sheet Location) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Derivative [Line Items]
Derivative liabilities (current liabilities)	$ (2)		$ (7)
Derivative liabilities (non-current liabilities)	(11)		(11)
Derivatives Designated As Hedging Instruments [Member]
Derivative [Line Items]
Derivative liabilities (current liabilities)	(2)	[1]	(5)	[1]
Net Derivative (liability) asset	(2)	[1]	(5)	[1]
Other Derivative Instruments [Member]
Derivative [Line Items]
Derivative liabilities (current liabilities)	(2)		(8)
Derivative liabilities (non-current liabilities)	(11)		(11)
Net Derivative (liability) asset	(13)		(19)
Gross Derivative Instruments [Member]
Derivative [Line Items]
Derivative liabilities (current liabilities)	(4)		(13)
Derivative liabilities (non-current liabilities)	(11)		(11)
Net Derivative (liability) asset	(15)		(24)
Effects Of Cash Collateral And Netting [Member]
Derivative [Line Items]
Derivative liabilities (current liabilities)	2		6
Net Derivative (liability) asset	2		6
Net Derivative Instruments [Member]
Derivative [Line Items]
Derivative liabilities (current liabilities)	(2)		(7)
Derivative liabilities (non-current liabilities)	(11)		(11)
Net Derivative (liability) asset	(13)		(18)
Discontinued Operations [Member]
Derivative [Line Items]
Net Derivative (liability) asset	(8)		(12)
Discontinued Operations [Member] | Derivatives Designated As Hedging Instruments [Member]
Derivative [Line Items]
Derivative liabilities (current liabilities)			(5)	[1]
Derivative liabilities (non-current liabilities)			(1)	[1]
Net Derivative (liability) asset			(6)	[1]
Discontinued Operations [Member] | Other Derivative Instruments [Member]
Derivative [Line Items]
Derivative liabilities (current liabilities)	(7)		(5)
Derivative liabilities (non-current liabilities)	(1)		(1)
Net Derivative (liability) asset	(8)		(6)
Discontinued Operations [Member] | Gross Derivative Instruments [Member]
Derivative [Line Items]
Derivative liabilities (current liabilities)	(7)		(10)
Derivative liabilities (non-current liabilities)	(1)		(2)
Net Derivative (liability) asset	(8)		(12)
Discontinued Operations [Member] | Effects Of Cash Collateral And Netting [Member]
Derivative [Line Items]
Derivative liabilities (current liabilities)	7		10
Derivative liabilities (non-current liabilities)	1		2
Net Derivative (liability) asset	8		12
Discontinued Operations [Member] | Net Derivative Instruments [Member]
Derivative [Line Items]
Derivative liabilities (current liabilities)
Derivative liabilities (non-current liabilities)
Net Derivative (liability) asset

[1] Amounts included in Derivatives Designated as Hedging Instruments primarily consist of derivatives that were designated as cash flow hedges prior to Pepco Energy Services' election to discontinue cash flow hedge accounting for these derivatives.