Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities
Net income	$ 685,016us-gaap_ProfitLoss	$ 610,425us-gaap_ProfitLoss	$ 385,555us-gaap_ProfitLoss
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	208,486	157,808	144,541
Provision for doubtful accounts	301us-gaap_ProvisionForDoubtfulAccounts	5,514us-gaap_ProvisionForDoubtfulAccounts	229us-gaap_ProvisionForDoubtfulAccounts
Amortization of debt issuance costs	1,673us-gaap_AmortizationOfFinancingCosts	1,459us-gaap_AmortizationOfFinancingCosts	1,514us-gaap_AmortizationOfFinancingCosts
Stock-based compensation expense	9,261us-gaap_ShareBasedCompensation	6,966us-gaap_ShareBasedCompensation	6,127us-gaap_ShareBasedCompensation
Loss from disposition of fixed assets	4,181us-gaap_GainLossOnDispositionOfAssets	5,039us-gaap_GainLossOnDispositionOfAssets	3,886us-gaap_GainLossOnDispositionOfAssets
Gain from sales of equity securities	0	0	(16,429)
Impairment of equity method investment	6,747	0	0
Write-off of debt issuance costs	0	0	1,277
Deferred income taxes	58,967us-gaap_DeferredIncomeTaxExpenseBenefit	93,732us-gaap_DeferredIncomeTaxExpenseBenefit	(5,793)us-gaap_DeferredIncomeTaxExpenseBenefit
Windfall tax benefits from share-based payment arrangements	(6,704)	(5,449)	(11,967)
(Income) loss from equity method investments, net of dividends	(424)	199	3,005
Other loss, net	275	391	0
Changes in operating assets and liabilities
Accounts receivable	33,161	(14,830)	6,450
Inventories	51,087us-gaap_IncreaseDecreaseInInventories	(46,633)us-gaap_IncreaseDecreaseInInventories	91,479us-gaap_IncreaseDecreaseInInventories
Prepaid expenses and other current assets	7,461	(475)	(2,205)
Accounts payable	(97,237)	13,820	(12,725)
Accrued liabilities	74,989	(15,147)	32,381
Other, net	(4,864)	(60,090)	(15,238)
Net cash provided by operating activities	1,032,376	752,729	612,087
Cash flows from investing activities
Acquisition of business, net of cash acquired	(611,087)	(178,309)	0
Additions to equity investments	0	(23,338)	0
Additions to property, plant and equipment	(431,104)	(679,222)	(386,882)
Construction of assets pending sale-leaseback	0	(136)	(4,308)
Proceeds from disposition of assets	181	151	471
Proceeds from repayment of loan acquired	45,923	0	0
Proceeds from repayment of loan to affiliate	0	167	1,192
Proceeds from sale-leaseback of assets	0	0	2,304
Proceeds from sales and maturities of securities	342,045	252,519	47,655
Purchase of securities	(117,332)us-gaap_PaymentsToAcquireInvestments	(367,150)us-gaap_PaymentsToAcquireInvestments	(127,834)us-gaap_PaymentsToAcquireInvestments
Settlements of derivative instruments	1,831	6,920	(431)
Net cash used for investing activities	(773,205)	(1,002,238)	(466,971)
Cash flows from financing activities
Capitalized debt issuance costs	(1,186)us-gaap_PaymentsOfDebtIssuanceCosts	0us-gaap_PaymentsOfDebtIssuanceCosts	(2,221)us-gaap_PaymentsOfDebtIssuanceCosts
Dividends paid	(77,656)us-gaap_PaymentsOfDividendsCommonStock	(55,236)us-gaap_PaymentsOfDividendsCommonStock	(285,521)us-gaap_PaymentsOfDividendsCommonStock
Distributions to noncontrolling interests	(2,204)us-gaap_PaymentsToMinorityShareholders	0us-gaap_PaymentsToMinorityShareholders	0us-gaap_PaymentsToMinorityShareholders
Net proceeds from issuance of Westlake Chemical Partners LP common units	286,088	0	0
Proceeds from debt issuance	0	0	248,818
Proceeds from exercise of stock options	5,524	3,437	10,369
Repayment of debt	0us-gaap_RepaymentsOfLongTermDebt	0us-gaap_RepaymentsOfLongTermDebt	(250,000)us-gaap_RepaymentsOfLongTermDebt
Repurchase of common stock for treasury	(52,630)	(32,918)	(10,784)
Utilization of restricted cash	0	0	96,433
Windfall tax benefits from share-based payment arrangements	6,704	5,449	11,967
Net cash provided by (used for) financing activities	164,640	(79,268)	(180,939)
Effect of exchange rate changes on cash and cash equivalents	(4,511)	0	0
Net increase (decrease) in cash and cash equivalents	419,300	(328,777)	(35,823)
Cash and cash equivalents at beginning of the year	461,301	790,078	825,901
Cash and cash equivalents at end of the year	$ 880,601	$ 461,301	$ 790,078

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- Definition

The cash outflow associated with the purchase of all investments (debt, security, other) during the period.

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- Definition

The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

+ References

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- Definition

Amount of cash outflow to a noncontrolling interest. Includes, but not limited to, reduction of noncontrolling interest ownership. Excludes dividends paid to the noncontrolling interest.

+ References

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

The cash inflow from the issuance of common limited partners units during the period.

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Data Type:	xbrli:monetaryItemType
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- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ References

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- Definition

Amount of cash inflow (outflow) from long-term debt by a related party. Related parties, include, but are not limited to, affiliates, owners or officers and their immediate families, and pension trusts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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- Definition

The net cash inflow or outflow from cash and cash items that are not available for withdrawal or usage.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

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-Publisher FASB

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-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

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- Definition

The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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-Publisher FASB

-Name Accounting Standards Codification

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-Section 45

-Paragraph 11

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-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (a),(b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

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- Definition

The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

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- Definition

The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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-Subparagraph (j)

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-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (a)

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- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

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-Paragraph 4K

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-Topic 810

-SubTopic 10

-Section 55

-Paragraph 4J

-URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686

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- Definition

Amount of expense related to write-down of receivables to the amount expected to be collected. Includes, but is not limited to, accounts receivable and notes receivable.

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- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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- Definition

The gross proceeds received from the asset(s) sold in connection with the transaction involving the sale of property to another party and the lease of the property back to the seller less the costs incurred in connection with the transaction, such as closing and deferred financing costs.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 40

-Section 55

-Paragraph 51

-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51840-112757

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 40

-Section 55

-Paragraph 52

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 40

-Section 55

-Paragraph 50

-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51831-112757

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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- Definition

The increase (decrease) during the reporting period in the aggregate value of prepaid expenses and other current assets.

+ References

No definition available.

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- Definition

The cash outflow associated with the construction of long-lived assets pending financing through a sale-leaseback.

+ References

No definition available.

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Namespace Prefix:	wlk_
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- Definition

Proceeds From (Repayments of) Acquired Loan

+ References

No definition available.

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