Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Current Assets
Allowance for doubtful accounts - trade receivables	$ 6	$ 9
Accumulated depreciation	2,039	1,816
Cash and cash equivalents (variable interest entity restricted - 2015: $7; 2014: $1)	967	780
Trade receivables - third party and affiliates	706	801
Property, plant and equipment (net of accumulated depreciation - 2015: $2,039; 2014: $1,816; variable interest entity restricted - 2015: $772; 2014: $530)	3,609	3,733
Other assets (variable interest entity restricted - 2015: $13; 2014: $29)	300	355
Intangible assets, net (variable interest entity restricted - 2015: $27; 2014: $0)	$ 125	$ 132
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	19,916,490	13,266,625
Common stock, par value	$ 0.0001
Series A common stock, $0.0001 par value, 400,000,000 shares authorized (2015: 166,698,787 issued and 146,782,297 outstanding; 2014: 166,169,335 issued and 152,902,710 outstanding)
Stockholders' Equity
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	166,698,787	166,169,335
Common stock, shares outstanding	146,782,297	152,902,710
Series B common stock, $0.0001 par value, 100,000,000 shares authorized (2015 and 2014: 0 issued and outstanding)
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 (variable interest entity restricted - 2015: $7; 2014: $1)	$ 7	$ 1
Trade receivables - third party and affiliates	6	0
Property, plant and equipment (net of accumulated depreciation - 2015: $2,039; 2014: $1,816; variable interest entity restricted - 2015: $772; 2014: $530)	772	530
Other assets (variable interest entity restricted - 2015: $13; 2014: $29)	13	29
Intangible assets, net (variable interest entity restricted - 2015: $27; 2014: $0)	$ 27	$ 0