Guarantor Disclosures (Condensed Consolidating Financial Information Balance Sheets) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,026,569	$ 880,601	$ 876,067	$ 461,301
Accounts receivable, net	600,722	560,666
Inventories	486,297	525,776
Prepaid expenses and other current assets	23,018	11,807
Deferred income taxes	29,634	32,437
Total current assets	2,166,240	2,011,287
Property, plant and equipment, net	2,855,508	2,757,557
Equity investments	37,746	61,305
Other assets, net	351,516	383,841
Total assets	5,411,010	5,213,990
Accounts payable		261,062
Accounts and notes payable	282,978	261,062
Accrued liabilities	251,680	276,118
Total current liabilities	534,658	537,180
Long-term debt	764,056	763,997
Deferred income taxes	532,344	536,066
Other liabilities	162,777	174,859
Total liabilities	1,993,835	2,012,102
Total Westlake Chemical Corporation stockholders' equity	3,123,388	2,911,511
Noncontrolling interests	293,787	290,377
Total equity	3,417,175	3,201,888	2,728,073	2,418,603
Total liabilities and equity	5,411,010	5,213,990
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	756,385	655,947	833,650	420,948
Accounts receivable, net	13,335	8,451
Inventories	0	0
Prepaid expenses and other current assets	136	172
Deferred income taxes	409	409
Total current assets	770,265	664,979
Property, plant and equipment, net	0	0
Equity investments	4,690,426	4,033,378
Other assets, net	18,920	30,543
Total assets	5,479,611	4,728,900
Accounts payable		1,055,527
Accounts and notes payable	1,594,555
Accrued liabilities	8,501	8,754
Total current liabilities	1,603,056	1,064,281
Long-term debt	753,167	753,108
Deferred income taxes	0	0
Other liabilities	0	0
Total liabilities	2,356,223	1,817,389
Total Westlake Chemical Corporation stockholders' equity	3,123,388	2,911,511
Noncontrolling interests	0	0
Total equity	3,123,388	2,911,511
Total liabilities and equity	5,479,611	4,728,900
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	3,923	3,057	8,819	6,227
Accounts receivable, net	1,995,787	1,454,709
Inventories	376,750	414,975
Prepaid expenses and other current assets	20,981	9,485
Deferred income taxes	29,832	29,832
Total current assets	2,427,273	1,912,058
Property, plant and equipment, net	1,520,734	1,477,515
Equity investments	1,228,964	1,237,080
Other assets, net	300,172	387,325
Total assets	5,477,143	5,013,978
Accounts payable		160,834
Accounts and notes payable	145,719
Accrued liabilities	173,112	203,608
Total current liabilities	318,831	364,442
Long-term debt	10,889	10,889
Deferred income taxes	498,993	497,919
Other liabilities	39,553	43,452
Total liabilities	868,266	916,702
Total Westlake Chemical Corporation stockholders' equity	4,608,877	4,097,276
Noncontrolling interests	0	0
Total equity	4,608,877	4,097,276
Total liabilities and equity	5,477,143	5,013,978
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	133,890	131,545	0	0
Accounts receivable, net	57,957	56,049
Inventories	3,856	6,634
Prepaid expenses and other current assets	30	212
Deferred income taxes	0	0
Total current assets	195,733	194,440
Property, plant and equipment, net	914,270	842,057
Equity investments	0	0
Other assets, net	50,018	57,733
Total assets	1,160,021	1,094,230
Accounts payable		17,680
Accounts and notes payable	36,339
Accrued liabilities	16,441	11,225
Total current liabilities	52,780	28,905
Long-term debt	145,651	227,638
Deferred income taxes	1,614	1,848
Other liabilities	0	0
Total liabilities	200,045	258,391
Total Westlake Chemical Corporation stockholders' equity	959,976	835,839
Noncontrolling interests	0	0
Total equity	959,976	835,839
Total liabilities and equity	1,160,021	1,094,230
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	132,371	90,052	33,598	34,126
Accounts receivable, net	144,560	135,133
Inventories	105,691	104,167
Prepaid expenses and other current assets	4,132	1,938
Deferred income taxes	279	2,196
Total current assets	387,033	333,486
Property, plant and equipment, net	420,504	437,985
Equity investments	467,530	352,550
Other assets, net	133,840	141,948
Total assets	1,408,907	1,265,969
Accounts payable		95,856
Accounts and notes payable	104,954
Accrued liabilities	69,101	77,372
Total current liabilities	174,055	173,228
Long-term debt	0	0
Deferred income taxes	37,520	42,369
Other liabilities	123,224	131,407
Total liabilities	334,799	347,004
Total Westlake Chemical Corporation stockholders' equity	780,321	628,588
Noncontrolling interests	293,787	290,377
Total equity	1,074,108	918,965
Total liabilities and equity	1,408,907	1,265,969
Eliminations
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0	$ 0	$ 0
Accounts receivable, net	(1,610,917)	(1,093,676)
Inventories	0	0
Prepaid expenses and other current assets	(2,261)	0
Deferred income taxes	(886)	0
Total current assets	(1,614,064)	(1,093,676)
Property, plant and equipment, net	0	0
Equity investments	(6,349,174)	(5,561,703)
Other assets, net	(151,434)	(233,708)
Total assets	(8,114,672)	(6,889,087)
Accounts payable		(1,068,835)
Accounts and notes payable	(1,598,589)
Accrued liabilities	(15,475)	(24,841)
Total current liabilities	(1,614,064)	(1,093,676)
Long-term debt	(145,651)	(227,638)
Deferred income taxes	(5,783)	(6,070)
Other liabilities	0	0
Total liabilities	(1,765,498)	(1,327,384)
Total Westlake Chemical Corporation stockholders' equity	(6,349,174)	(5,561,703)
Noncontrolling interests	0	0
Total equity	(6,349,174)	(5,561,703)
Total liabilities and equity	$ (8,114,672)	$ (6,889,087)