Acquisition (Pro Forma Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Business Combinations [Abstract]
Net sales	$ 5,345,365	$ 6,053,330
Net income	284,324	595,442
Net income (loss) attributable to noncontrolling interest	16,404	(5,953)
Net income attributable to Westlake Chemical Corporation	$ 267,920	$ 601,395
Basic (in dollars per share)	$ 2.06	$ 4.54
Diluted (in dollars per share)	$ 2.05	$ 4.52