Derivative Financial Instruments By Balance Sheet Location (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Derivatives Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	$ 57	$ 75
Footnotes to Derivatives Balance Sheet Location [Abstract]
Collateral Already Posted Aggregate Fair Value	147	105
Cash flow hedges [Member] | Asset Financial Instruments Current [Member]
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	9	3
Cash flow hedges [Member] | Asset Financial Instruments Noncurrent [Member]
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	0	0
Cash flow hedges [Member] | Liability Financial Instruments Current [Member]
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	(12)	(5)
Cash flow hedges [Member] | Liability Financial Instruments Noncurrent [Member]
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	(13)	0
Cash flow hedges [Member] | Interest rate swap contracts [Member]
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	13	0
Derivatives not designated as hedging instruments [Member] | Asset Financial Instruments Current [Member]
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	728	541
Derivatives not designated as hedging instruments [Member] | Asset Financial Instruments Noncurrent [Member]
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	137	105
Derivatives not designated as hedging instruments [Member] | Liability Financial Instruments Current [Member]
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	(689)	(489)
Derivatives not designated as hedging instruments [Member] | Liability Financial Instruments Noncurrent [Member]
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	$ (116)	$ (80)