Derivative Instruments And Hedging Activities (Fair Value Of Derivative Instruments By Balance Sheet Location) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Derivative [Line Items]
Derivative assets (current assets)	$ 5		$ 45
Total Derivative assets	192		114
Derivative liabilities (current liabilities)	(26)		(66)
Derivative liabilities (non-current liabilities)	(6)		(21)
Derivatives Designated As Hedging Instruments [Member]
Derivative [Line Items]
Derivative assets (current assets)	17	[1]	40
Derivative assets (non-current assets)			16
Total Derivative assets	17	[1]	56
Derivative liabilities (current liabilities)	(55)	[1]	(125)
Derivative liabilities (non-current liabilities)	(11)	[1]	(68)
Total Derivative liabilities	(66)	[1]	(193)
Net Derivative (liability) asset	(49)	[1]	(137)
Other Derivative Instruments [Member]
Derivative [Line Items]
Derivative assets (current assets)	6	[2]	43
Derivative assets (non-current assets)	1	[2]	3
Total Derivative assets	7	[2]	46
Derivative liabilities (current liabilities)	(48)	[2]	(63)
Derivative liabilities (non-current liabilities)	(10)	[2]	(10)
Total Derivative liabilities	(58)	[2]	(73)
Net Derivative (liability) asset	(51)	[2]	(27)
Gross Derivative Instruments [Member]
Derivative [Line Items]
Derivative assets (current assets)	23		83
Derivative assets (non-current assets)	1		19
Total Derivative assets	24		102
Derivative liabilities (current liabilities)	(103)		(188)
Derivative liabilities (non-current liabilities)	(21)		(78)
Total Derivative liabilities	(124)		(266)
Net Derivative (liability) asset	(100)		(164)
Effects Of Cash Collateral And Netting [Member]
Derivative [Line Items]
Derivative assets (current assets)	(18)		(38)
Derivative assets (non-current assets)	(1)		(19)
Total Derivative assets	(19)		(57)
Derivative liabilities (current liabilities)	77		122
Derivative liabilities (non-current liabilities)	15		57
Total Derivative liabilities	92		179
Net Derivative (liability) asset	73		122
Net Derivative Instruments [Member]
Derivative [Line Items]
Derivative assets (current assets)	5		45
Total Derivative assets	5		45
Derivative liabilities (current liabilities)	(26)		(66)
Derivative liabilities (non-current liabilities)	(6)		(21)
Total Derivative liabilities	(32)		(87)
Net Derivative (liability) asset	$ (27)		$ (42)

[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 derivatives that are not accounted for as cash flow hedges subsequent to Pepco Energy Services' election to discontinue cash flow hedge accounting.