Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Condensed Financial Statements, Captions [Line Items]
Net income	$ 269,163	$ 203,314
Depreciation and amortization	76,295	71,978
Deferred income taxes	60,425	6,720
Net changes in working capital and other	(150,403)	34,134
Net cash provided by operating activities	255,480	316,146
Acquisition of business	(178,309)	0
Additons to equity investments	(6,113)	0
Additions to property, plant and equipment	(297,873)	(140,568)
Construction of assets pending sale-leaseback	(136)	(1,760)
Proceeds from disposition of assets	62	415
Proceeds from repayment of loan to affiliate	167	596
Proceeds from sales of equity securities	209,785	46,027
Purchase of securities and other investments	(114,881)	(2,961)
Settlements of derivative instruments	(1,588)	511
Net cash used for investing activities	(388,886)	(97,740)
Intercompany financing	0	0
Capitalized debt issuance costs	0	(98)
Dividends paid	(25,120)	(9,838)
Proceeds from exercise of stock options	2,656	4,508
Repurchase of common stock for treasury	(13,283)	(10,784)
Utilization of restricted cash	0	75,975
Windfall tax benefits from share-based payment arrangements	4,576	6,468
Net cash provided by financing activities	(31,171)	66,231
Net increase in cash and cash equivalents	(164,577)	284,637
Cash and cash equivalents at beginning of period	790,078	825,901
Cash and cash equivalents at end of period	625,501	1,110,538
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Net income	269,163	203,314
Depreciation and amortization	730	801
Deferred income taxes	(1,230)	(717)
Net changes in working capital and other	(279,039)	(220,440)
Net cash provided by operating activities	(10,376)	(17,042)
Acquisition of business	0
Additons to equity investments	0
Additions to property, plant and equipment	0	0
Construction of assets pending sale-leaseback	0	0
Proceeds from disposition of assets	0	0
Proceeds from repayment of loan to affiliate	0	0
Proceeds from sales of equity securities	209,785	3
Purchase of securities and other investments	(114,881)	0
Settlements of derivative instruments	0	0
Net cash used for investing activities	94,904	3
Intercompany financing	(214,927)	230,680
Capitalized debt issuance costs		(98)
Dividends paid	(25,120)	(9,838)
Proceeds from exercise of stock options	2,656	4,508
Repurchase of common stock for treasury	(13,283)	(10,784)
Utilization of restricted cash		75,975
Windfall tax benefits from share-based payment arrangements	4,576	6,468
Net cash provided by financing activities	(246,098)	296,911
Net increase in cash and cash equivalents	(161,570)	279,872
Cash and cash equivalents at beginning of period	753,881	803,320
Cash and cash equivalents at end of period	592,311	1,083,192
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income	276,222	214,245
Depreciation and amortization	74,298	69,514
Deferred income taxes	61,610	7,270
Net changes in working capital and other	(153,604)	45,051
Net cash provided by operating activities	258,526	336,080
Acquisition of business	(178,309)
Additons to equity investments	(6,113)
Additions to property, plant and equipment	(295,859)	(139,876)
Construction of assets pending sale-leaseback	(136)	(1,760)
Proceeds from disposition of assets	2	412
Proceeds from repayment of loan to affiliate	0	0
Proceeds from sales of equity securities	0	46,024
Purchase of securities and other investments	0	(2,961)
Settlements of derivative instruments	(1,588)	511
Net cash used for investing activities	(482,003)	(97,650)
Intercompany financing	219,968	(236,256)
Capitalized debt issuance costs		0
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0	0
Utilization of restricted cash		0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	219,968	(236,256)
Net increase in cash and cash equivalents	(3,509)	2,174
Cash and cash equivalents at beginning of period	6,973	2,517
Cash and cash equivalents at end of period	3,464	4,691
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income	(1,444)	(292)
Depreciation and amortization	1,267	1,663
Deferred income taxes	45	167
Net changes in working capital and other	7,462	(4,430)
Net cash provided by operating activities	7,330	(2,892)
Acquisition of business	0
Additons to equity investments	0
Additions to property, plant and equipment	(2,014)	(692)
Construction of assets pending sale-leaseback	0	0
Proceeds from disposition of assets	60	3
Proceeds from repayment of loan to affiliate	167	596
Proceeds from sales of equity securities	0	0
Purchase of securities and other investments	0	0
Settlements of derivative instruments	0	0
Net cash used for investing activities	(1,787)	(93)
Intercompany financing	(5,041)	5,576
Capitalized debt issuance costs		0
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0	0
Utilization of restricted cash		0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	(5,041)	5,576
Net increase in cash and cash equivalents	502	2,591
Cash and cash equivalents at beginning of period	29,224	20,064
Cash and cash equivalents at end of period	29,726	22,655
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income	(274,778)	(213,953)
Depreciation and amortization	0	0
Deferred income taxes	0	0
Net changes in working capital and other	274,778	213,953
Net cash provided by operating activities	0	0
Acquisition of business	0
Additons to equity investments	0
Additions to property, plant and equipment	0	0
Construction of assets pending sale-leaseback	0	0
Proceeds from disposition of assets	0	0
Proceeds from repayment of loan to affiliate	0	0
Proceeds from sales of equity securities	0	0
Purchase of securities and other investments	0	0
Settlements of derivative instruments	0	0
Net cash used for investing activities	0	0
Intercompany financing		0
Capitalized debt issuance costs		0
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0	0
Utilization of restricted cash		0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	0	0
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$ 0	$ 0