Earnings per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$ 205,095	$ 169,443	$ 351,437	$ 327,475
Less: Net income attributable to participating securities	(253)	(360)	(457)	(746)
Net income attributable to common shareholders	$ 204,842	$ 169,083	$ 350,980	$ 326,729