Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net income	$ 497,631	$ 439,453	$ 610,425
Depreciation and amortization	149,566	117,387
Deferred income taxes	34,459	83,443
Net changes in working capital and other	94,468	(92,783)
Net cash provided by operating activities	776,124	547,500
Acquisition of business, net of cash acquired	(611,087)	(178,309)
Additions to equity investments	0	(23,338)
Additions to property, plant and equipment	(311,183)	(498,290)
Construction of assets pending sale-leaseback	0	(136)
Proceeds from disposition of assets	145	78
Proceeds from repayment of loan acquired	45,923	0
Proceeds from repayment of loan to affiliate	0	167
Proceeds from sale and maturities of securities	342,045	239,764
Purchase of securities and other investments	(117,332)	(232,286)
Settlements of derivative instruments	(689)	(2,297)
Net cash used for investing activities	(652,178)	(694,647)
Intercompany financing	0	0
Net distributions prior to WLKP initial public offering	0	0
Capitalized debt issuance costs	(1,167)
Dividends paid	(55,690)	(40,204)
Net proceeds from issuance of Westlake Chemical Partners LP common units	286,088	0
Purchase of limited partner interests	0
Proceeds from exercise of stock options	5,502	3,182
Repurchase of common stock for treasury	(9,495)	(19,409)
Windfall tax benefits from share-based payment arrangements	6,670	5,056
Net cash provided by financing activities	231,908	(51,375)
Effect of exchange rate changes on cash	(3,687)	0
Net increase in cash and cash equivalents	352,167	(198,522)
Cash and cash equivalents at beginning of period	461,301	790,078	790,078
Cash and cash equivalents at end of period	813,468	591,556	461,301
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Net income	495,232	439,453
Depreciation and amortization	1,172	1,094
Deferred income taxes	(418)	(1,102)
Net changes in working capital and other	(509,862)	(458,336)
Net cash provided by operating activities	(13,876)	(18,891)
Acquisition of business, net of cash acquired	0	0
Additions to equity investments		0
Additions to property, plant and equipment	0	0
Construction of assets pending sale-leaseback		0
Proceeds from disposition of assets	0	0
Proceeds from repayment of loan acquired	0
Proceeds from repayment of loan to affiliate		0
Proceeds from sale and maturities of securities	342,045	239,764
Purchase of securities and other investments	(117,332)	(232,286)
Settlements of derivative instruments	0	0
Net cash used for investing activities	224,713	7,478
Intercompany financing	75,104	(130,832)
Net distributions prior to WLKP initial public offering	0	0
Capitalized debt issuance costs	(1,167)
Dividends paid	(55,690)	(40,204)
Net proceeds from issuance of Westlake Chemical Partners LP common units	0
Purchase of limited partner interests	0
Proceeds from exercise of stock options	5,502	3,182
Repurchase of common stock for treasury	(9,495)	(19,409)
Windfall tax benefits from share-based payment arrangements	6,670	5,056
Net cash provided by financing activities	20,924	(182,207)
Effect of exchange rate changes on cash	0
Net increase in cash and cash equivalents	231,761	(193,620)
Cash and cash equivalents at beginning of period	420,948	753,881	753,881
Cash and cash equivalents at end of period	652,709	560,261
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income	509,404	446,858
Depreciation and amortization	82,597	59,893
Deferred income taxes	26,991	57,279
Net changes in working capital and other	(919,521)	(421,066)
Net cash provided by operating activities	(300,529)	142,964
Acquisition of business, net of cash acquired	0	(178,309)
Additions to equity investments		(23,338)
Additions to property, plant and equipment	(160,147)	(337,158)
Construction of assets pending sale-leaseback		(136)
Proceeds from disposition of assets	144	6
Proceeds from repayment of loan acquired	0
Proceeds from repayment of loan to affiliate		0
Proceeds from sale and maturities of securities	0	0
Purchase of securities and other investments	0	0
Settlements of derivative instruments	(556)	0
Net cash used for investing activities	(160,559)	(538,935)
Intercompany financing	(143,325)	(28,499)
Net distributions prior to WLKP initial public offering	448,101	421,991
Capitalized debt issuance costs	0
Dividends paid	151,729	0
Net proceeds from issuance of Westlake Chemical Partners LP common units	0
Purchase of limited partner interests	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	456,505	393,492
Effect of exchange rate changes on cash	0
Net increase in cash and cash equivalents	(4,583)	(2,479)
Cash and cash equivalents at beginning of period	6,227	6,973	6,973
Cash and cash equivalents at end of period	1,644	4,494
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Net income	416,737	402,340
Depreciation and amortization	58,501	54,539
Deferred income taxes	8,267	27,253
Net changes in working capital and other	1,641	(68,604)
Net cash provided by operating activities	485,146	415,528
Acquisition of business, net of cash acquired	0	0
Additions to equity investments		0
Additions to property, plant and equipment	(144,348)	(158,869)
Construction of assets pending sale-leaseback		0
Proceeds from disposition of assets	0	0
Proceeds from repayment of loan acquired	0
Proceeds from repayment of loan to affiliate		0
Proceeds from sale and maturities of securities	0	0
Purchase of securities and other investments	0	0
Settlements of derivative instruments	(133)	(2,297)
Net cash used for investing activities	(144,481)	(161,166)
Intercompany financing	62,221	167,629
Net distributions prior to WLKP initial public offering	(448,101)	(421,991)
Capitalized debt issuance costs	0
Dividends paid	(151,729)	0
Net proceeds from issuance of Westlake Chemical Partners LP common units	0
Purchase of limited partner interests	286,088
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	(251,521)	(254,362)
Effect of exchange rate changes on cash	0
Net increase in cash and cash equivalents	89,144	0
Cash and cash equivalents at beginning of period	0	0	0
Cash and cash equivalents at end of period	89,144	0
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income	(1,441)	(1,639)
Depreciation and amortization	7,296	1,861
Deferred income taxes	(381)	13
Net changes in working capital and other	599,909	7,664
Net cash provided by operating activities	605,383	7,899
Acquisition of business, net of cash acquired	(611,087)	0
Additions to equity investments		0
Additions to property, plant and equipment	(6,688)	(2,263)
Construction of assets pending sale-leaseback		0
Proceeds from disposition of assets	1	72
Proceeds from repayment of loan acquired	45,923
Proceeds from repayment of loan to affiliate		167
Proceeds from sale and maturities of securities	0	0
Purchase of securities and other investments	0	0
Settlements of derivative instruments	0	0
Net cash used for investing activities	(571,851)	(2,024)
Intercompany financing	6,000	(8,298)
Net distributions prior to WLKP initial public offering	0	0
Capitalized debt issuance costs	0
Dividends paid	0	0
Net proceeds from issuance of Westlake Chemical Partners LP common units	286,088
Purchase of limited partner interests	(286,088)
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	6,000	(8,298)
Effect of exchange rate changes on cash	(3,687)
Net increase in cash and cash equivalents	35,845	(2,423)
Cash and cash equivalents at beginning of period	34,126	29,224	29,224
Cash and cash equivalents at end of period	69,971	26,801
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income	(922,301)	(847,559)
Depreciation and amortization	0	0
Deferred income taxes	0	0
Net changes in working capital and other	922,301	847,559
Net cash provided by operating activities	0	0
Acquisition of business, net of cash acquired	0	0
Additions to equity investments		0
Additions to property, plant and equipment	0	0
Construction of assets pending sale-leaseback		0
Proceeds from disposition of assets	0	0
Proceeds from repayment of loan acquired	0
Proceeds from repayment of loan to affiliate		0
Proceeds from sale and maturities of 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	0
Net distributions prior to WLKP initial public offering	0	0
Capitalized debt issuance costs	0
Dividends paid	0	0
Net proceeds from issuance of Westlake Chemical Partners LP common units	0
Purchase of limited partner interests	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0	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	0
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0	0
Cash and cash equivalents at end of period	$ 0	$ 0