Derivative Instruments And Hedging Activities (Fair Value Of Derivative Instruments By Balance Sheet Location) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Derivative [Line Items]
Derivative assets (current assets)	$ 6		$ 5
Total Derivative assets	150		192
Derivative liabilities (current liabilities)	(25)		(26)
Derivative liabilities (non-current liabilities)	(2)		(6)
Derivatives Designated As Hedging Instruments [Member]
Derivative [Line Items]
Derivative assets (current assets)	9	[1]	17	[1]
Total Derivative assets	9	[1]	17	[1]
Derivative liabilities (current liabilities)	(38)	[1]	(55)	[1]
Derivative liabilities (non-current liabilities)	(8)	[1]	(11)	[1]
Total Derivative liabilities	(46)	[1]	(66)	[1]
Net Derivative (liability) asset	(37)	[1]	(49)	[1]
Other Derivative Instruments [Member]
Derivative [Line Items]
Derivative assets (current assets)	8	[2]	6	[2]
Derivative assets (non-current assets)	1	[2]	1	[2]
Total Derivative assets	9	[2]	7	[2]
Derivative liabilities (current liabilities)	(50)	[2]	(48)	[2]
Derivative liabilities (non-current liabilities)	(6)	[2]	(10)	[2]
Total Derivative liabilities	(56)	[2]	(58)	[2]
Net Derivative (liability) asset	(47)	[2]	(51)	[2]
Gross Derivative Instruments [Member]
Derivative [Line Items]
Derivative assets (current assets)	17		23
Derivative assets (non-current assets)	1		1
Total Derivative assets	18		24
Derivative liabilities (current liabilities)	(88)		(103)
Derivative liabilities (non-current liabilities)	(14)		(21)
Total Derivative liabilities	(102)		(124)
Net Derivative (liability) asset	(84)		(100)
Effects Of Cash Collateral And Netting [Member]
Derivative [Line Items]
Derivative assets (current assets)	(11)		(18)
Derivative assets (non-current assets)			(1)
Total Derivative assets	(11)		(19)
Derivative liabilities (current liabilities)	63		77
Derivative liabilities (non-current liabilities)	12		15
Total Derivative liabilities	75		92
Net Derivative (liability) asset	64		73
Net Derivative Instruments [Member]
Derivative [Line Items]
Derivative assets (current assets)	6		5
Derivative assets (non-current assets)	1
Total Derivative assets	7		5
Derivative liabilities (current liabilities)	(25)		(26)
Derivative liabilities (non-current liabilities)	(2)		(6)
Total Derivative liabilities	(27)		(32)
Net Derivative (liability) asset	$ (20)		$ (27)

[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.

[2] Amounts included in Other Derivative Instruments include gains or losses on gas derivatives that are not accounted for as cash flow hedges subsequent to Pepco Energy Services' election to discontinue cash flow hedge accounting.