Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	$ 784	$ 915	$ 639	$ 577
Short-term investments	360	794
Net derivative contracts	1	(35)
Long-term debt converted to floating interest rates by interest rate swaps - net	(10)	(39)
Quoted prices in active markets for identical assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	784	915
Short-term investments	360	794
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
Net derivative contracts	1	(35)
Long-term debt converted to floating interest rates by interest rate swaps - net	(10)	(39)
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
Net derivative contracts	0	0
Long-term debt converted to floating interest rates by interest rate swaps - net	$ 0	$ 0