Guarantor Disclosures (Condensed Consolidating Financial Information Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 945,649	$ 880,601	$ 532,643	$ 461,301
Accounts receivable, net	527,127	560,666
Inventories	480,380	525,776
Prepaid expenses and other current assets	18,018	11,807
Deferred income taxes	30,988	32,437
Total current assets	2,002,162	2,011,287
Property, plant and equipment, net	2,751,486	2,757,557
Equity investments	64,721	61,305
Other assets, net	361,416	383,841
Total assets	5,179,785	5,213,990
Accounts payable	247,493	261,062
Accrued liabilities	205,714	276,118
Total current liabilities	453,207	537,180
Long-term debt	764,027	763,997
Deferred income taxes	534,679	536,066
Other liabilities	157,130	174,859
Total liabilities	1,909,043	2,012,102
Total Westlake Chemical Corporation stockholders' equity	2,979,858	2,911,511
Noncontrolling interests	290,884	290,377
Total equity	3,270,742	3,201,888	2,568,572	2,418,603
Total liabilities and equity	5,179,785	5,213,990
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	701,622	655,947	490,508	420,948
Accounts receivable, net	11,605	8,451
Inventories	0	0
Prepaid expenses and other current assets	92	172
Deferred income taxes	409	409
Total current assets	713,728	664,979
Property, plant and equipment, net	0	0
Equity investments	4,123,427	4,033,378
Other assets, net	31,209	30,543
Total assets	4,868,364	4,728,900
Accounts payable	1,118,864	1,055,527
Accrued liabilities	16,504	8,754
Total current liabilities	1,135,368	1,064,281
Long-term debt	753,138	753,108
Deferred income taxes	0	0
Other liabilities	0	0
Total liabilities	1,888,506	1,817,389
Total Westlake Chemical Corporation stockholders' equity	2,979,858	2,911,511
Noncontrolling interests	0	0
Total equity	2,979,858	2,911,511
Total liabilities and equity	4,868,364	4,728,900
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	2,606	3,057	7,896	6,227
Accounts receivable, net	1,497,572	1,454,709
Inventories	395,664	414,975
Prepaid expenses and other current assets	18,236	9,485
Deferred income taxes	29,832	29,832
Total current assets	1,943,910	1,912,058
Property, plant and equipment, net	1,500,234	1,477,515
Equity investments	1,232,093	1,237,080
Other assets, net	415,180	387,325
Total assets	5,091,417	5,013,978
Accounts payable	153,645	160,834
Accrued liabilities	150,074	203,608
Total current liabilities	303,719	364,442
Long-term debt	10,889	10,889
Deferred income taxes	503,540	497,919
Other liabilities	38,625	43,452
Total liabilities	856,773	916,702
Total Westlake Chemical Corporation stockholders' equity	4,234,644	4,097,276
Noncontrolling interests	0	0
Total equity	4,234,644	4,097,276
Total liabilities and equity	5,091,417	5,013,978
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	143,005	131,545	0	0
Accounts receivable, net	54,979	56,049
Inventories	4,564	6,634
Prepaid expenses and other current assets	122	212
Deferred income taxes	0	0
Total current assets	202,670	194,440
Property, plant and equipment, net	866,546	842,057
Equity investments	0	0
Other assets, net	53,832	57,733
Total assets	1,123,048	1,094,230
Accounts payable	27,395	17,680
Accrued liabilities	6,104	11,225
Total current liabilities	33,499	28,905
Long-term debt	257,829	227,638
Deferred income taxes	1,902	1,848
Other liabilities	0	0
Total liabilities	293,230	258,391
Total Westlake Chemical Corporation stockholders' equity	829,818	835,839
Noncontrolling interests	0	0
Total equity	829,818	835,839
Total liabilities and equity	1,123,048	1,094,230
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	98,416	90,052	34,239	34,126
Accounts receivable, net	128,116	135,133
Inventories	80,152	104,167
Prepaid expenses and other current assets	2,160	1,938
Deferred income taxes	747	2,196
Total current assets	309,591	333,486
Property, plant and equipment, net	384,706	437,985
Equity investments	351,048	352,550
Other assets, net	124,633	141,948
Total assets	1,169,978	1,265,969
Accounts payable	89,383	95,856
Accrued liabilities	58,975	77,372
Total current liabilities	148,358	173,228
Long-term debt	0	0
Deferred income taxes	34,846	42,369
Other liabilities	118,505	131,407
Total liabilities	301,709	347,004
Total Westlake Chemical Corporation stockholders' equity	577,385	628,588
Noncontrolling interests	290,884	290,377
Total equity	868,269	918,965
Total liabilities and equity	1,169,978	1,265,969
Eliminations
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	(1,165,145)	(1,093,676)
Inventories	0	0
Prepaid expenses and other current assets	(2,592)	0
Deferred income taxes	0	0
Total current assets	(1,167,737)	(1,093,676)
Property, plant and equipment, net	0	0
Equity investments	(5,641,847)	(5,561,703)
Other assets, net	(263,438)	(233,708)
Total assets	(7,073,022)	(6,889,087)
Accounts payable	(1,141,794)	(1,068,835)
Accrued liabilities	(25,943)	(24,841)
Total current liabilities	(1,167,737)	(1,093,676)
Long-term debt	(257,829)	(227,638)
Deferred income taxes	(5,609)	(6,070)
Other liabilities	0	0
Total liabilities	(1,431,175)	(1,327,384)
Total Westlake Chemical Corporation stockholders' equity	(5,641,847)	(5,561,703)
Noncontrolling interests	0	0
Total equity	(5,641,847)	(5,561,703)
Total liabilities and equity	$ (7,073,022)	$ (6,889,087)