Guarantor Disclosures (Condensed Consolidating Financial Information Balance Sheet) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 880,601	$ 461,301	$ 790,078	$ 825,901
Marketable securities	0	239,388
Accounts receivable, net	560,666	428,457
Inventories	525,776	471,879
Prepaid expenses and other current assets	11,807	13,888
Deferred income taxes	32,437	34,169
Total current assets	2,011,287	1,649,082
Property, plant and equipment, net	2,757,557	2,088,014
Equity investments	61,305	66,875
Other assets, net	383,841	256,938
Total assets	5,213,990	4,060,909
Accounts payable	261,062	249,613
Accrued liabilities	276,118	155,245
Total current liabilities	537,180	404,858
Long-term debt	763,997	763,879
Deferred income taxes	536,066	437,976
Other liabilities	174,859	35,593
Liabilities	2,012,102	1,642,306
Stockholders' equity	2,911,511	2,418,603
Noncontrolling interests	290,377	0
Total equity	3,201,888	2,418,603	1,872,256	1,756,312
Total liabilities and equity	5,213,990	4,060,909
Westlake Chemical Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	655,947	420,948	753,881	803,320
Marketable securities		239,388
Accounts receivable, net	8,451	3,879
Inventories	0	0
Prepaid expenses and other current assets	172	778
Deferred income taxes	409	441
Total current assets	664,979	665,434
Property, plant and equipment, net	0	0
Equity investments	4,033,378	2,815,752
Other assets, net	30,543	15,393
Total assets	4,728,900	3,496,579
Accounts payable	1,055,527	316,652
Accrued liabilities	8,754	8,334
Total current liabilities	1,064,281	324,986
Long-term debt	753,108	752,990
Deferred income taxes	0	0
Other liabilities	0	0
Liabilities	1,817,389
Stockholders' equity	2,911,511	2,418,603
Noncontrolling interests	0
Total equity	2,911,511
Total liabilities and equity	4,728,900	3,496,579
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	3,057	6,227	6,973	2,517
Marketable securities		0
Accounts receivable, net	1,454,709	666,344
Inventories	414,975	339,929
Prepaid expenses and other current assets	9,485	11,055
Deferred income taxes	29,832	28,974
Total current assets	1,912,058	1,052,529
Property, plant and equipment, net	1,477,515	1,318,119
Equity investments	1,237,080	636,461
Other assets, net	387,325	423,901
Total assets	5,013,978	3,431,010
Accounts payable	160,834	100,570
Accrued liabilities	203,608	134,452
Total current liabilities	364,442	235,022
Long-term debt	10,889	10,889
Deferred income taxes	497,919	260,171
Other liabilities	43,452	34,571
Liabilities	916,702
Stockholders' equity	4,097,276	2,890,357
Noncontrolling interests	0
Total equity	4,097,276
Total liabilities and equity	5,013,978	3,431,010
Westlake Chemical OpCo LP [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	131,545	0	0	0
Marketable securities		0
Accounts receivable, net	56,049	71,812
Inventories	6,634	116,377
Prepaid expenses and other current assets	212	257
Deferred income taxes	0	4,448
Total current assets	194,440	192,894
Property, plant and equipment, net	842,057	762,972
Equity investments	0	10,411
Other assets, net	57,733	75,197
Total assets	1,094,230	1,041,474
Accounts payable	17,680	122,564
Accrued liabilities	11,225	26,688
Total current liabilities	28,905	149,252
Long-term debt	227,638	252,973
Deferred income taxes	1,848	182,855
Other liabilities	0	962
Liabilities	258,391
Stockholders' equity	835,839	455,432
Noncontrolling interests	0
Total equity	835,839
Total liabilities and equity	1,094,230	1,041,474
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	90,052	34,126	29,224	20,064
Marketable securities		0
Accounts receivable, net	135,133	2,755
Inventories	104,167	15,573
Prepaid expenses and other current assets	1,938	1,798
Deferred income taxes	2,196	306
Total current assets	333,486	54,558
Property, plant and equipment, net	437,985	6,923
Equity investments	352,550	31,518
Other assets, net	141,948	1,199
Total assets	1,265,969	94,198
Accounts payable	95,856	10,649
Accrued liabilities	77,372	1,282
Total current liabilities	173,228	11,931
Long-term debt	0	0
Deferred income taxes	42,369	729
Other liabilities	131,407	60
Liabilities	347,004
Stockholders' equity	628,588	81,478
Noncontrolling interests	290,377
Total equity	918,965
Total liabilities and equity	1,265,969	94,198
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0	0	0
Marketable securities		0
Accounts receivable, net	(1,093,676)	(316,333)
Inventories	0	0
Prepaid expenses and other current assets	0	0
Deferred income taxes	0	0
Total current assets	(1,093,676)	(316,333)
Property, plant and equipment, net	0	0
Equity investments	(5,561,703)	(3,427,267)
Other assets, net	(233,708)	(258,752)
Total assets	(6,889,087)	(4,002,352)
Accounts payable	(1,068,835)	(300,822)
Accrued liabilities	(24,841)	(15,511)
Total current liabilities	(1,093,676)	(316,333)
Long-term debt	(227,638)	(252,973)
Deferred income taxes	(6,070)	(5,779)
Other liabilities	0	0
Liabilities	(1,327,384)
Stockholders' equity	(5,561,703)	(3,427,267)
Noncontrolling interests	0
Total equity	(5,561,703)
Total liabilities and equity	$ (6,889,087)	$ (4,002,352)