Fair Value Measurements (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	$ 278	$ 333
Summary of financial instruments recognized at fair value and fair value measurement used
Short-term investments	536	838
Net derivative contracts	25	69
Long-term debt converted to floating interest rates by interest rate swaps	67	42
Carrying value of long-term debt and current portion of long-term debt	3,689	3,386
Fair value of long-term debt and current portion of long-term debt	4,324	3,787
Quoted prices in active markets for identical assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	278	333
Summary of financial instruments recognized at fair value and fair value measurement used
Short-term investments	536	838
Net derivative contracts	0	0
Long-term debt converted to floating interest rates by interest rate swaps	0	0
Other Observable inputs Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	0	0
Summary of financial instruments recognized at fair value and fair value measurement used
Short-term investments	0	0
Net derivative contracts	25	69
Long-term debt converted to floating interest rates by interest rate swaps	67	42
Unobservable inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	0	0
Summary of financial instruments recognized at fair value and fair value measurement used
Short-term investments	0	0
Net derivative contracts	0	0
Long-term debt converted to floating interest rates by interest rate swaps	$ 0	$ 0