Acquisitions (Pro Forma Information) (Details) - USD ($) $ / shares in Units, $ in Millions	8 Months Ended	12 Months Ended
	Aug. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Net sales		$ 7,081	$ 7,793
Net income		397	663
Net income (loss) attributable to noncontrolling interest		23	(2)
Net income attributable to Westlake Chemical Corporation		$ 374	$ 665
Basic (in dollars per share)		$ 2.88	$ 5.02
Diluted (in dollars per share)		$ 2.86	$ 5.00
Axiall Corporation [Member]
Business Acquisition [Line Items]
Divestitures	$ 27
Restructuring Costs	23
Legal and Settlement Claims, net	$ 23