Earnings per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$ 210,832	$ 65,662	$ 501,849	$ 299,914
Net income attributable to participating securities	(1,117)	(294)	(2,630)	(1,347)
Net income attributable to common shareholders	$ 209,715	$ 65,368	$ 499,219	$ 298,567