Derivative Instruments And Hedging Activities (Fair Value Of Derivative Instruments By Balance Sheet Location) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Derivative Assets (current assets)	$ 15		$ 45
Total Derivative Assets	198		114
Derivative Liabilities (current liabilities)	(33)		(66)
Derivative Liabilities (non-current liabilities)	(8)		(21)
Derivatives Designated As Hedging Instruments [Member]
Derivative Assets (current assets)	22	[1]	40
Derivative Assets (non-current assets)			16
Total Derivative Assets	22	[1]	56
Derivative Liabilities (current liabilities)	(72)	[1]	(125)
Derivative Liabilities (non-current liabilities)	(18)	[1]	(68)
Total Derivative Liabilities	(90)	[1]	(193)
Net Derivative (Liability) Asset	(68)	[1]	(137)
Other Derivative Instruments [Member]
Derivative Assets (current assets)	20	[1]	43
Derivative Assets (non-current assets)	2	[1]	3
Total Derivative Assets	22	[1]	46
Derivative Liabilities (current liabilities)	(44)	[1]	(63)
Derivative Liabilities (non-current liabilities)	(11)	[1]	(10)
Total Derivative Liabilities	(55)	[1]	(73)
Net Derivative (Liability) Asset	(33)	[1]	(27)
Gross Derivative Instruments [Member]
Derivative Assets (current assets)	42		83
Derivative Assets (non-current assets)	2		19
Total Derivative Assets	44		102
Derivative Liabilities (current liabilities)	(116)		(188)
Derivative Liabilities (non-current liabilities)	(29)		(78)
Total Derivative Liabilities	(145)		(266)
Net Derivative (Liability) Asset	(101)		(164)
Effects Of Cash Collateral And Netting [Member]
Derivative Assets (current assets)	(27)		(38)
Derivative Assets (non-current assets)	(2)		(19)
Total Derivative Assets	(29)		(57)
Derivative Liabilities (current liabilities)	83		122
Derivative Liabilities (non-current liabilities)	21		57
Total Derivative Liabilities	104		179
Net Derivative (Liability) Asset	75		122
Net Derivative Instruments [Member]
Derivative Assets (current assets)	15		45
Total Derivative Assets	15		45
Derivative Liabilities (current liabilities)	(33)		(66)
Derivative Liabilities (non-current liabilities)	(8)		(21)
Total Derivative Liabilities	(41)		(87)
Net Derivative (Liability) Asset	$ (26)		$ (42)

[1] Amounts included in Derivatives Designated as Hedging Instruments primarily consist of natural gas derivatives that were designated as cash flow hedges prior to the January 1, 2011 election to discontinue cash flow hedge accounting for these derivatives. Amounts included in Other Derivative Instruments primarily consist of gains or losses on natural gas derivatives that are not accounted for as cash flow hedges after the January 1, 2011 election to discontinue cash flow hedge accounting.