Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 150,407us-gaap_ProfitLoss	$ 158,032us-gaap_ProfitLoss
Pension and other post-retirement benefits liability
Amortization of benefits liability	652	219
Income tax provision on pension and other post-retirement benefits liability	(225)	(84)
Foreign currency translation adjustments	(59,698)	(898)
Available-for-sale investments
Unrealized holding gains on investments	1,626	2,467
Reclassification of net realized loss to net income	0	25
Income tax provision on available-for-sale investments	(584)	(895)
Other comprehensive (loss) income	(58,229)	834
Comprehensive income	92,178	158,866
Comprehensive income attributable to noncontrolling interests, net of tax	4,065	0
Comprehensive income (loss) attributable to Westlake Chemical Corporation	$ 88,113us-gaap_ComprehensiveIncomeNetOfTax	$ 158,866us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), attributable to noncontrolling interests. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount of tax (expense) benefit, after reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans, attributable to parent entity.

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Amount after tax, before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount before tax and reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities and unrealized holding gain (loss) related to transfers of securities into the available-for-sale classification and out of the held-to-maturity classification.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount before tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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Amortization of benefits liability included in other comprehensive income, before tax.

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Amount of tax expense (benefit), including reclassification adjustments, of appreciation (loss) in value of available-for-sale securities. Excluded amounts related to other than temporary impairment (OTTI) loss.

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