Condensed Consolidating Financial Information Statement of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 203,314	$ 164,593
Depreciation and amortization	71,978	66,246
Deferred income taxes	6,720	15,949
Net changes in working capital and other	40,602	(121,483)
Net cash (used for) provided by operating activities	322,614	125,305
Additions to property, plant and equipment	(140,568)	(69,178)
Construction of assets pending sale-leaseback	(1,760)
Proceeds from disposition of assets	415	2,456
Proceeds from repayment of loan to affiliate	596	596
Proceeds from sales of equity securities	46,027
Purchase of investments	(2,961)
Settlements of derivative instruments	511	(222)
Net cash provided by (used for) investing activities	(97,740)	(66,348)
Capitalized debt issuance costs	(98)
Dividends paid	(9,838)	(8,446)
Proceeds from exercise of stock options	4,508	5,323
Repurchase of common stock for treasury	(10,784)
Utilization of restricted cash	75,975	26,189
Net cash provided by (used for) financing activities	59,763	23,066
Net increase (decrease) in cash and cash equivalents	284,637	82,023
Cash and cash equivalents at beginning of period	825,901	630,299
Cash and cash equivalents at end of period	1,110,538	712,322
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	203,314	164,593
Depreciation and amortization	801	863
Deferred income taxes	(717)	(126)
Net changes in working capital and other	(213,972)	(179,938)
Net cash (used for) provided by operating activities	(10,574)	(14,608)
Proceeds from sales of equity securities	3
Net cash provided by (used for) investing activities	3
Intercompany financing	230,680	73,784
Capitalized debt issuance costs	(98)
Dividends paid	(9,838)	(8,446)
Proceeds from exercise of stock options	4,508	5,323
Repurchase of common stock for treasury	(10,784)
Utilization of restricted cash	75,975	26,189
Net cash provided by (used for) financing activities	290,443	96,850
Net increase (decrease) in cash and cash equivalents	279,872	82,242
Cash and cash equivalents at beginning of period	803,320	611,158
Cash and cash equivalents at end of period	1,083,192	693,400
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	214,245	180,894
Depreciation and amortization	69,514	63,484
Deferred income taxes	7,270	16,573
Net changes in working capital and other	45,051	(120,387)
Net cash (used for) provided by operating activities	336,080	140,564
Additions to property, plant and equipment	(139,876)	(68,383)
Construction of assets pending sale-leaseback	(1,760)
Proceeds from disposition of assets	412	2,456
Proceeds from sales of equity securities	46,024
Purchase of investments	(2,961)
Settlements of derivative instruments	511	(222)
Net cash provided by (used for) investing activities	(97,650)	(66,149)
Intercompany financing	(236,256)	(73,658)
Net cash provided by (used for) financing activities	(236,256)	(73,658)
Net increase (decrease) in cash and cash equivalents	2,174	757
Cash and cash equivalents at beginning of period	2,517	53
Cash and cash equivalents at end of period	4,691	810
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(292)	(965)
Depreciation and amortization	1,663	1,899
Deferred income taxes	167	(498)
Net changes in working capital and other	(4,430)	(1,087)
Net cash (used for) provided by operating activities	(2,892)	(651)
Additions to property, plant and equipment	(692)	(795)
Proceeds from disposition of assets	3
Proceeds from repayment of loan to affiliate	596	596
Net cash provided by (used for) investing activities	(93)	(199)
Intercompany financing	5,576	(126)
Net cash provided by (used for) financing activities	5,576	(126)
Net increase (decrease) in cash and cash equivalents	2,591	(976)
Cash and cash equivalents at beginning of period	20,064	19,088
Cash and cash equivalents at end of period	22,655	18,112
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(213,953)	(179,929)
Net changes in working capital and other	$ 213,953	$ 179,929