Earnings per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$ 183,604	$ 167,757	$ 535,041	$ 495,232
Less: Net income attributable to participating securities	(195)	(353)	(653)	(1,099)
Net income attributable to common shareholders	$ 183,409	$ 167,404	$ 534,388	$ 494,133