Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	$ 525	$ 385	$ 282	$ 333
Short-term investments	652	699
Summary of financial instruments recognized at fair value and fair value measurement used
Net derivative contracts	73	46
Long-term debt converted to floating interest rates by interest rate swaps - net	80	66
Carrying value of long-term debt and current portion of long-term debt	4,287	3,687
Fair value of long-term debt and current portion of long-term debt	4,820	4,273
Quoted prices in active markets for identical assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	525	385
Short-term investments	652	699
Summary of financial instruments recognized at fair value and fair value measurement used
Net derivative contracts	0	0
Long-term debt converted to floating interest rates by interest rate swaps - net	0	0
Other Observable inputs Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	0	0
Short-term investments	0	0
Summary of financial instruments recognized at fair value and fair value measurement used
Net derivative contracts	73	46
Long-term debt converted to floating interest rates by interest rate swaps - net	80	66
Unobservable inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	0	0
Short-term investments	0	0
Summary of financial instruments recognized at fair value and fair value measurement used
Net derivative contracts	0	0
Long-term debt converted to floating interest rates by interest rate swaps - net	$ 0	$ 0