Acquisition (Pro Forma) (Details) - USD ($) $ / shares in Units, $ in Thousands	8 Months Ended	9 Months Ended
Aug. 30, 2016	Sep. 30, 2016
Business Acquisition, Pro Forma Information [Line Items]
Net sales		$ 5,345,365
Net income		277,567
Net income attributable to noncontrolling interest		16,404
Net income attributable to Westlake Chemical Corporation		$ 261,163
Basic (in dollars per share)		$ 2.01
Diluted (in dollars per share)		$ 2.00
Axiall Corporation [Member]
Business Acquisition, Pro Forma Information [Line Items]
Divestitures	$ 26,666
Restructuring costs	22,881
Legal and settlement claims, net	$ 23,376

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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-Name Accounting Standards Codification
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