Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 290,278	$ 232,523
Depreciation and amortization	110,750	99,533
Deferred income taxes	4,385	19,435
Net changes in working capital and other	95,210	(107,138)
Net cash (used for) provided by operating activities	500,623	244,353
Additions to property, plant and equipment	(235,463)	(111,823)
Construction of assets pending sale-leaseback	(5,484)	0
Proceeds from disposition of assets	435	2,456
Proceeds from repayment of loan to affiliate	763	763
Proceeds from sales of equity securities	47,655	0
Purchase of investments	(2,961)	(29,877)
Settlements of derivative instruments	471	(331)
Net cash provided by (used for) investing activities	(194,584)	(138,812)
Capitalized debt issuance costs	(2,221)	(2,540)
Dividends paid	(22,345)	(13,359)
Proceeds from borrowings	248,818	0
Proceeds from exercise of stock options	6,627	5,323
Repayment of borrowings	(250,000)	0
Repurchase of common stock for treasury	(10,784)	(19)
Utilization of restricted cash	96,433	33,694
Net cash provided by (used for) financing activities	66,528	23,099
Net increase (decrease) in cash and cash equivalents	372,567	128,640
Cash and cash equivalents at beginning of period	825,901	630,299
Cash and cash equivalents at end of period	1,198,468	758,939
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	290,278	232,523
Depreciation and amortization	1,149	1,290
Deferred income taxes	(176)	(1,430)
Net changes in working capital and other	(310,163)	(255,859)
Net cash (used for) provided by operating activities	(18,912)	(23,476)
Proceeds from sales of equity securities	3
Net cash provided by (used for) investing activities	3	0
Intercompany financing	317,185	129,251
Capitalized debt issuance costs	(2,221)	(2,540)
Dividends paid	(22,345)	(13,359)
Proceeds from borrowings	248,818
Proceeds from exercise of stock options	6,627	5,323
Repayment of borrowings	(250,000)
Repurchase of common stock for treasury	(10,784)	(19)
Utilization of restricted cash	96,433	33,694
Net cash provided by (used for) financing activities	383,713	152,350
Net increase (decrease) in cash and cash equivalents	364,804	128,874
Cash and cash equivalents at beginning of period	803,320	611,158
Cash and cash equivalents at end of period	1,168,124	740,032
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	312,038	257,286
Depreciation and amortization	107,191	95,486
Deferred income taxes	3,932	21,010
Net changes in working capital and other	95,909	(104,494)
Net cash (used for) provided by operating activities	519,070	269,288
Additions to property, plant and equipment	(234,713)	(110,887)
Construction of assets pending sale-leaseback	(5,484)
Proceeds from disposition of assets	414	2,453
Proceeds from sales of equity securities	47,652
Purchase of investments	(2,961)	(29,877)
Settlements of derivative instruments	471	(331)
Net cash provided by (used for) investing activities	(194,621)	(138,642)
Intercompany financing	(321,273)	(129,158)
Net cash provided by (used for) financing activities	(321,273)	(129,158)
Net increase (decrease) in cash and cash equivalents	3,176	1,488
Cash and cash equivalents at beginning of period	2,517	53
Cash and cash equivalents at end of period	5,693	1,541
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(676)	(1,479)
Depreciation and amortization	2,410	2,757
Deferred income taxes	629	(145)
Net changes in working capital and other	(1,898)	(2,592)
Net cash (used for) provided by operating activities	465	(1,459)
Additions to property, plant and equipment	(750)	(936)
Proceeds from disposition of assets	21	3
Proceeds from repayment of loan to affiliate	763	763
Net cash provided by (used for) investing activities	34	(170)
Intercompany financing	4,088	(93)
Net cash provided by (used for) financing activities	4,088	(93)
Net increase (decrease) in cash and cash equivalents	4,587	(1,722)
Cash and cash equivalents at beginning of period	20,064	19,088
Cash and cash equivalents at end of period	24,651	17,366
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(311,362)	(255,807)
Net changes in working capital and other	$ 311,362	$ 255,807