Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net income	$ 150,407	$ 158,032
Depreciation and amortization	59,142	46,337
Deferred income taxes	5,331	8,275
Net changes in working capital and other	(24,324)	(139)
Net cash provided by operating activities	190,556	212,505
Additions to property, plant and equipment	(95,822)	(110,741)
Proceeds from disposition of assets	0	12
Proceeds from sales and maturities of securities	0	30,119
Purchase of securities	0	(49,025)
Settlements of derivative instruments	(833)	(409)
Net cash used for investing activities	(96,655)	(130,044)
Intercompany financing	0	0
Net distributions prior to WLKP initial public offering		0
Distribution Made to Limited Partner, Cash Distributions Paid	(3,558)
Dividends paid	(21,964)	(16,789)
Proceeds from exercise of stock options	157	2,158
Repurchase of common stock for treasury	(2,000)
Windfall tax benefits from share-based payment arrangements	1,701	3,512
Net cash provided by financing activities	(25,664)	(11,119)
Effect of exchange rate changes on cash and cash equivalents	(3,189)	0
Net increase in cash and cash equivalents	65,048	71,342
Cash and cash equivalents at beginning of period	880,601	461,301
Cash and cash equivalents at end of period	945,649	532,643
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Net income	146,342	158,032
Depreciation and amortization	501	365
Deferred income taxes	(124)	(162)
Net changes in working capital and other	(151,572)	(165,553)
Net cash provided by operating activities	(4,853)	(7,318)
Additions to property, plant and equipment	0	0
Proceeds from disposition of assets		0
Proceeds from sales and maturities of securities		30,119
Purchase of securities		(49,025)
Settlements of derivative instruments	0	0
Net cash used for investing activities	0	(18,906)
Intercompany financing	72,634	106,903
Net distributions prior to WLKP initial public offering		0
Distribution Made to Limited Partner, Cash Distributions Paid	0
Dividends paid	(21,964)	(16,789)
Proceeds from exercise of stock options	157	2,158
Repurchase of common stock for treasury	(2,000)
Windfall tax benefits from share-based payment arrangements	1,701	3,512
Net cash provided by financing activities	50,528	95,784
Effect of exchange rate changes on cash and cash equivalents	0
Net increase in cash and cash equivalents	45,675	69,560
Cash and cash equivalents at beginning of period	655,947	420,948
Cash and cash equivalents at end of period	701,622	490,508
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income	137,127	161,813
Depreciation and amortization	29,592	26,394
Deferred income taxes	6,431	5,220
Net changes in working capital and other	(114,779)	(169,342)
Net cash provided by operating activities	58,371	24,085
Additions to property, plant and equipment	(47,385)	(59,254)
Proceeds from disposition of assets		12
Proceeds from sales and maturities of securities		0
Purchase of securities		0
Settlements of derivative instruments	(833)	0
Net cash used for investing activities	(48,218)	(59,242)
Intercompany financing	(99,765)	(155,387)
Net distributions prior to WLKP initial public offering		192,213
Distribution Made to Limited Partner, Cash Distributions Paid	89,161
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	(10,604)	36,826
Effect of exchange rate changes on cash and cash equivalents	0
Net increase in cash and cash equivalents	(451)	1,669
Cash and cash equivalents at beginning of period	3,057	6,227
Cash and cash equivalents at end of period	2,606	7,896
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Net income	89,343	143,874
Depreciation and amortization	19,803	19,014
Deferred income taxes	54	3,267
Net changes in working capital and other	6,973	31,731
Net cash provided by operating activities	116,173	197,886
Additions to property, plant and equipment	(39,540)	(51,305)
Proceeds from disposition of assets		0
Proceeds from sales and maturities of securities		0
Purchase of securities		0
Settlements of derivative instruments	0	(409)
Net cash used for investing activities	(39,540)	(51,714)
Intercompany financing	30,191	46,041
Net distributions prior to WLKP initial public offering		(192,213)
Distribution Made to Limited Partner, Cash Distributions Paid	(95,364)
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	(65,173)	(146,172)
Effect of exchange rate changes on cash and cash equivalents	0
Net increase in cash and cash equivalents	11,460	0
Cash and cash equivalents at beginning of period	131,545	0
Cash and cash equivalents at end of period	143,005	0
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income	16,255	(852)
Depreciation and amortization	9,246	564
Deferred income taxes	(1,030)	(50)
Net changes in working capital and other	(3,606)	(1,810)
Net cash provided by operating activities	20,865	(2,148)
Additions to property, plant and equipment	(8,897)	(182)
Proceeds from sales and maturities of securities		0
Purchase of securities		0
Settlements of derivative instruments	0	0
Net cash used for investing activities	(8,897)	(182)
Intercompany financing	(3,060)	2,443
Net distributions prior to WLKP initial public offering		0
Distribution Made to Limited Partner, Cash Distributions Paid	2,645
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	(415)	2,443
Effect of exchange rate changes on cash and cash equivalents	(3,189)
Net increase in cash and cash equivalents	8,364	113
Cash and cash equivalents at beginning of period	90,052	34,126
Cash and cash equivalents at end of period	98,416	34,239
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income	(238,660)	(304,835)
Depreciation and amortization	0	0
Deferred income taxes	0	0
Net changes in working capital and other	238,660	304,835
Net cash provided by operating activities	0	0
Additions to property, plant and equipment	0	0
Proceeds from disposition of assets		0
Proceeds from sales and maturities of securities		0
Purchase of securities		0
Settlements of derivative instruments	0	0
Net cash used for investing activities	0	0
Intercompany financing	0	0
Net distributions prior to WLKP initial public offering		0
Distribution Made to Limited Partner, Cash Distributions Paid	0
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	0	0
Effect of exchange rate changes on cash and cash equivalents	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