Unaudited Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 501	$ 638
Allowance for doubtful accounts - trade receivables	6	6
Trade receivables - third party and affiliates	886	801
Accumulated depreciation	2,307	2,239
Property, plant and equipment (net of accumulated depreciation - 2017: $2,307; 2016: $2,239; variable interest entity restricted - 2017: $724; 2016: $734)	3,571	3,577
Other assets	308	307
Accumulated amortization	531	524
Intangible assets (net of accumulated amortization - 2017: $531; 2016: $524; variable interest entity restricted - 2017: $26; 2016: $26)	$ 192	$ 194
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	28,412,876	26,950,910
Series A common stock, $0.0001 par value, 400,000,000 shares authorized (2017: 167,965,429 issued and 139,552,553 outstanding; 2016: 167,611,357 issued and 140,660,447 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	167,965,429	167,611,357
Common stock, shares outstanding	139,552,553	140,660,447
Series B common stock, $0.0001 par value, 100,000,000 shares authorized (2017 and 2016: 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	$ 13	$ 18
Trade receivables - third party and affiliates	5	4
Property, plant and equipment (net of accumulated depreciation - 2017: $2,307; 2016: $2,239; variable interest entity restricted - 2017: $724; 2016: $734)	724	734
Other assets	8	9
Intangible assets (net of accumulated amortization - 2017: $531; 2016: $524; variable interest entity restricted - 2017: $26; 2016: $26)	$ 26	$ 26