Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Current Assets
Cash and cash equivalents	$ 1,064	$ 984
Allowance for doubtful accounts - trade receivables	9	9
Accumulated depreciation	1,770	1,672
Property, plant and equipment, net	3,577	3,425
Other assets	332	341
Stockholders' Equity
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Treasury stock, shares	10,798,434	8,928,137
Common stock, par value	$ 0.0001
Series A common stock, $0.0001 par value, 400,000,000 shares authorized (2014: 166,038,983 issued and 155,240,549 outstanding; 2013: 165,867,965 issued and 156,939,828 outstanding) [Member]
Stockholders' Equity
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	166,038,983	165,867,965
Common stock, shares outstanding	155,240,549	156,939,828
Series B common stock, $0.0001 par value, 100,000,000 shares authorized (2014 and 2013: 0 issued and outstanding) [Member]
Stockholders' Equity
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0
Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents	44
Property, plant and equipment, net	252
Other assets	$ 24