Guarantor Disclosures (Condensed Consolidating Financial Information Statement Of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 685,016	$ 610,425	$ 385,555
Depreciation and amortization	210,159	159,267	146,055
Deferred income taxes	58,967	93,732	(5,793)
Net changes in working capital and other	78,234	(110,695)	86,270
Net cash provided by operating activities	1,032,376	752,729	612,087
Additions to property, plant and equipment	(431,104)	(679,222)	(386,882)
Construction of assets pending sale-leaseback	0	(136)	(4,308)
Acquisition of business, net of cash acquired	(611,087)	(178,309)	0
Additions to equity investments	0	(23,338)	0
Proceeds from disposition of assets	181	151	471
Proceeds from repayment of loan acquired	45,923	0	0
Proceeds from repayment of loan to affiliate	0	167	1,192
Proceeds from sale-leaseback of assets	0	0	2,304
Proceeds from sales and maturities of equity securities	342,045	252,519	47,655
Purchase of securities	(117,332)	(367,150)	(127,834)
Settlements of derivative instruments	(1,831)	(6,920)	431
Net cash used for investing activities	(773,205)	(1,002,238)	(466,971)
Intercompany financing	0	0	0
Net distributions prior to WLKP initial public offering	0		0
Capitalized debt issuance costs	(1,186)	0	(2,221)
Dividends paid	(77,656)	(55,236)	(285,521)
Distribution Made to Limited Partner, Cash Distributions Paid	(2,204)
Proceeds from debt issuance	0	0	248,818
Net proceeds from issuance of Westlake Chemical Partners LP common units	286,088	0	0
Payments to Acquire Limited Partnership Interests	0
Proceeds from exercise of stock options	5,524	3,437	10,369
Repayment of debt	0	0	(250,000)
Repurchase of common stock for treasury	(52,630)	(32,918)	(10,784)
Utilization of restricted cash	0	0	96,433
Windfall tax benefits from share-based payment arrangements	6,704	5,449	11,967
Net cash provided by (used for) financing activities	164,640	(79,268)	(180,939)
Effect of exchange rate changes on cash and cash equivalents	(4,511)	0	0
Net increase (decrease) in cash and cash equivalents	419,300	(328,777)	(35,823)
Cash and cash equivalents at beginning of the year	461,301	790,078	825,901
Cash and cash equivalents at end of the year	880,601	461,301	790,078
Westlake Chemical Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	678,523	610,425	385,555
Depreciation and amortization	1,673	1,459	1,514
Deferred income taxes	(288)	74	45
Net changes in working capital and other	(706,043)	(622,194)	(422,199)
Net cash provided by operating activities	(26,135)	(10,236)	(35,085)
Additions to property, plant and equipment	0	0	0
Construction of assets pending sale-leaseback		0
Acquisition of business, net of cash acquired	0	0
Additions to equity investments		0
Proceeds from disposition of assets	0	0	0
Proceeds from repayment of loan acquired	0
Proceeds from repayment of loan to affiliate		0	0
Proceeds from sales and maturities of equity securities	342,045	252,519	3
Purchase of securities	(117,332)	(367,150)	(124,873)
Settlements of derivative instruments	0	0	0
Net cash used for investing activities	224,713	(114,631)	(124,870)
Intercompany financing	155,665	(128,798)	291,455
Net distributions prior to WLKP initial public offering	0	0	0
Capitalized debt issuance costs	(1,186)		(2,221)
Dividends paid	(77,656)	(55,236)	(285,521)
Distribution Made to Limited Partner, Cash Distributions Paid	0
Proceeds from debt issuance			248,818
Net proceeds from issuance of Westlake Chemical Partners LP common units	0
Payments to Acquire Limited Partnership Interests	0
Proceeds from exercise of stock options	5,524	3,437	10,369
Repayment of debt			(250,000)
Repurchase of common stock for treasury	(52,630)	(32,918)	(10,784)
Utilization of restricted cash			96,433
Windfall tax benefits from share-based payment arrangements	6,704	5,449	11,967
Net cash provided by (used for) financing activities	36,421	(208,066)	110,516
Effect of exchange rate changes on cash and cash equivalents	0
Net increase (decrease) in cash and cash equivalents	234,999	(332,933)	(49,439)
Cash and cash equivalents at beginning of the year	420,948	753,881	803,320
Cash and cash equivalents at end of the year	655,947	420,948	753,881
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	708,940	619,653	412,942
Depreciation and amortization	111,389	81,897	77,131
Deferred income taxes	55,344	56,787	2,134
Net changes in working capital and other	(1,077,982)	(607,033)	(345,730)
Net cash provided by operating activities	(202,309)	151,304	146,477
Additions to property, plant and equipment	(209,111)	(453,538)	(227,479)
Construction of assets pending sale-leaseback		(136)	(4,308)
Acquisition of business, net of cash acquired	0	(178,309)
Additions to equity investments		(23,338)
Proceeds from disposition of assets	180	75	449
Proceeds from repayment of loan acquired	0
Proceeds from repayment of loan to affiliate		0	0
Proceeds from sale-leaseback of assets			2,304
Proceeds from sales and maturities of equity securities	0	0	47,652
Purchase of securities	0	0	(2,961)
Settlements of derivative instruments	(1,698)	0	(1)
Net cash used for investing activities	(210,629)	(655,246)	(184,344)
Intercompany financing	(244,122)	(100,330)	(296,490)
Net distributions prior to WLKP initial public offering	448,101	603,526	338,813
Capitalized debt issuance costs	0		0
Dividends paid	151,729	0	0
Distribution Made to Limited Partner, Cash Distributions Paid	54,060
Proceeds from debt issuance			0
Net proceeds from issuance of Westlake Chemical Partners LP common units	0
Payments to Acquire Limited Partnership Interests	0
Proceeds from exercise of stock options	0	0	0
Repayment of debt			0
Repurchase of common stock for treasury	0	0	0
Utilization of restricted cash			0
Windfall tax benefits from share-based payment arrangements	0	0	0
Net cash provided by (used for) financing activities	409,768	503,196	42,323
Effect of exchange rate changes on cash and cash equivalents	0
Net increase (decrease) in cash and cash equivalents	(3,170)	(746)	4,456
Cash and cash equivalents at beginning of the year	6,227	6,973	2,517
Cash and cash equivalents at end of the year	3,057	6,227	6,973
Westlake Chemical OpCo LP [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	512,206	546,546	395,920
Depreciation and amortization	77,611	73,463	64,257
Deferred income taxes	8,608	37,054	(8,096)
Net changes in working capital and other	4,879	(54,554)	44,740
Net cash provided by operating activities	603,304	602,509	496,821
Additions to property, plant and equipment	(202,823)	(223,130)	(158,440)
Construction of assets pending sale-leaseback		0
Acquisition of business, net of cash acquired	0	0
Additions to equity investments		0
Proceeds from disposition of assets	0	0	0
Proceeds from repayment of loan acquired	0
Proceeds from repayment of loan to affiliate		0	0
Proceeds from sales and maturities of equity securities	0	0
Purchase of securities	0	0	0
Settlements of derivative instruments	(133)	(6,920)	432
Net cash used for investing activities	(202,956)	(230,050)	(158,008)
Intercompany financing	102,702	231,067	0
Net distributions prior to WLKP initial public offering	(448,101)	(603,526)	(338,813)
Capitalized debt issuance costs	0		0
Dividends paid	(151,729)	0	0
Distribution Made to Limited Partner, Cash Distributions Paid	(57,763)
Proceeds from debt issuance			0
Net proceeds from issuance of Westlake Chemical Partners LP common units	0
Payments to Acquire Limited Partnership Interests	286,088
Proceeds from exercise of stock options	0	0	0
Repayment of debt			0
Repurchase of common stock for treasury	0	0	0
Utilization of restricted cash			0
Windfall tax benefits from share-based payment arrangements	0	0	0
Net cash provided by (used for) financing activities	(268,803)	(372,459)	(338,813)
Effect of exchange rate changes on cash and cash equivalents	0
Net increase (decrease) in cash and cash equivalents	131,545	0	0
Cash and cash equivalents at beginning of the year	0	0	0
Cash and cash equivalents at end of the year	131,545	0	0
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(2,832)	(2,899)	(1,659)
Depreciation and amortization	19,486	2,448	3,153
Deferred income taxes	(4,697)	(183)	124
Net changes in working capital and other	645,559	9,786	2,256
Net cash provided by operating activities	657,516	9,152	3,874
Additions to property, plant and equipment	(19,170)	(2,554)	(963)
Construction of assets pending sale-leaseback		0
Acquisition of business, net of cash acquired	(611,087)	0
Additions to equity investments		0
Proceeds from disposition of assets	1	76	22
Proceeds from repayment of loan acquired	45,923
Proceeds from repayment of loan to affiliate		167	1,192
Proceeds from sales and maturities of equity securities	0	0
Purchase of securities	0	0	0
Settlements of derivative instruments	0	0	0
Net cash used for investing activities	(584,333)	(2,311)	251
Intercompany financing	(14,245)	(1,939)	5,035
Net distributions prior to WLKP initial public offering	0	0	0
Capitalized debt issuance costs	0		0
Dividends paid	0	0	0
Distribution Made to Limited Partner, Cash Distributions Paid	1,499
Proceeds from debt issuance			0
Net proceeds from issuance of Westlake Chemical Partners LP common units	286,088
Payments to Acquire Limited Partnership Interests	(286,088)
Proceeds from exercise of stock options	0	0	0
Repayment of debt			0
Repurchase of common stock for treasury	0	0	0
Utilization of restricted cash			0
Windfall tax benefits from share-based payment arrangements	0	0	0
Net cash provided by (used for) financing activities	(12,746)	(1,939)	5,035
Effect of exchange rate changes on cash and cash equivalents	(4,511)
Net increase (decrease) in cash and cash equivalents	55,926	4,902	9,160
Cash and cash equivalents at beginning of the year	34,126	29,224	20,064
Cash and cash equivalents at end of the year	90,052	34,126	29,224
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(1,211,821)	(1,163,300)	(807,203)
Depreciation and amortization	0	0	0
Deferred income taxes	0	0	0
Net changes in working capital and other	1,211,821	1,163,300	807,203
Net cash provided by operating activities	0	0	0
Additions to property, plant and equipment	0	0	0
Construction of assets pending sale-leaseback		0
Acquisition of business, net of cash acquired	0	0
Additions to equity investments		0
Proceeds from disposition of assets	0	0	0
Proceeds from repayment of loan acquired	0
Proceeds from repayment of loan to affiliate		0	0
Proceeds from sales and maturities of equity securities	0	0
Purchase of securities	0	0	0
Settlements of derivative instruments	0	0	0
Net cash used for investing activities	0	0	0
Intercompany financing			0
Net distributions prior to WLKP initial public offering	0	0	0
Capitalized debt issuance costs	0		0
Dividends paid	0	0	0
Distribution Made to Limited Partner, Cash Distributions Paid	0
Proceeds from debt issuance			0
Net proceeds from issuance of Westlake Chemical Partners LP common units	0
Payments to Acquire Limited Partnership Interests	0
Proceeds from exercise of stock options	0	0	0
Repayment of debt			0
Repurchase of common stock for treasury	0	0	0
Utilization of restricted cash			0
Windfall tax benefits from share-based payment arrangements	0	0	0
Net cash provided by (used for) financing activities	0	0	0
Effect of exchange rate changes on cash and cash equivalents	0
Net increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of the year	0	0	0
Cash and cash equivalents at end of the year	$ 0	$ 0	$ 0