Guarantor Disclosures (Condensed Consolidating Financial Information Balance Sheets) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 770,997	$ 662,525	$ 1,026,569	$ 880,601
Marketable securities	352,021	520,144
Accounts receivable, net	582,855	508,532
Inventories	448,526	434,060
Prepaid expenses and other current assets	35,642	14,489
Deferred income taxes	0	35,439
Total current assets	2,190,041	2,175,189
Property, plant and equipment, net	3,230,523	3,004,067
Equity investments	8,929	9,208
Other assets, net	491,071	380,821
Total assets	5,920,564	5,569,285
Accounts payable		235,329
Accounts and notes payable	307,116	235,329
Accrued liabilities	312,985	287,313
Total current liabilities	620,101	522,642
Long-term debt	758,453	758,148
Deferred income taxes	664,987	575,603
Other liabilities	139,587	150,961
Total liabilities	2,183,128	2,007,354
Total Westlake Chemical Corporation stockholders' equity	3,439,163	3,265,878
Noncontrolling interests	298,273	296,053
Total equity	3,737,436	3,561,931	3,417,175	3,201,888
Total liabilities and equity	5,920,564	5,569,285
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0	0	0
Marketable securities	0	0
Accounts receivable, net	(1,944,298)	(1,850,590)
Inventories	0	0
Prepaid expenses and other current assets	(4,238)	(2,879)
Deferred income taxes		0
Total current assets	(1,948,536)	(1,853,469)
Property, plant and equipment, net	0	0
Equity investments	(6,943,882)	(6,659,553)
Other assets, net	(412,282)	(255,232)
Total assets	(9,304,700)	(8,768,254)
Accounts payable		(1,825,865)
Accounts and notes payable	(1,918,178)
Accrued liabilities	(30,358)	(27,604)
Total current liabilities	(1,948,536)	(1,853,469)
Long-term debt	(379,997)	(248,665)
Deferred income taxes	(4,037)	(6,567)
Other liabilities	(28,248)	0
Total liabilities	(2,360,818)	(2,108,701)
Total Westlake Chemical Corporation stockholders' equity	(6,943,882)	(6,659,553)
Noncontrolling interests	0	0
Total equity	(6,943,882)	(6,659,553)
Total liabilities and equity	(9,304,700)	(8,768,254)
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	412,881	303,131	756,385	655,947
Marketable securities	352,021	520,144
Accounts receivable, net	15,228	10,943
Inventories	0	0
Prepaid expenses and other current assets	11,126	2,201
Deferred income taxes		702
Total current assets	791,256	837,121
Property, plant and equipment, net	0	0
Equity investments	5,269,364	4,991,167
Other assets, net	59,169	11,929
Total assets	6,119,789	5,840,217
Accounts payable		1,817,963
Accounts and notes payable	1,924,189
Accrued liabilities	8,873	9,117
Total current liabilities	1,933,062	1,827,080
Long-term debt	747,564	747,259
Deferred income taxes	0	0
Other liabilities	0	0
Total liabilities	2,680,626	2,574,339
Total Westlake Chemical Corporation stockholders' equity	3,439,163	3,265,878
Noncontrolling interests	0	0
Total equity	3,439,163	3,265,878
Total liabilities and equity	6,119,789	5,840,217
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	1,095	6,828	3,923	3,057
Marketable securities	0	0
Accounts receivable, net	2,306,348	2,183,276
Inventories	348,372	326,588
Prepaid expenses and other current assets	15,861	12,166
Deferred income taxes		32,787
Total current assets	2,671,676	2,561,645
Property, plant and equipment, net	1,606,327	1,567,897
Equity investments	1,211,547	1,207,679
Other assets, net	587,816	450,428
Total assets	6,077,366	5,787,649
Accounts payable		121,820
Accounts and notes payable	116,376
Accrued liabilities	164,520	195,785
Total current liabilities	280,896	317,605
Long-term debt	10,889	10,889
Deferred income taxes	618,716	532,837
Other liabilities	67,744	49,334
Total liabilities	978,245	910,665
Total Westlake Chemical Corporation stockholders' equity	5,099,121	4,876,984
Noncontrolling interests	0	0
Total equity	5,099,121	4,876,984
Total liabilities and equity	6,077,366	5,787,649
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	142,339	163,430	133,890	131,545
Marketable securities	0	0
Accounts receivable, net	68,738	51,582
Inventories	2,493	3,879
Prepaid expenses and other current assets	73	267
Deferred income taxes		0
Total current assets	213,643	219,158
Property, plant and equipment, net	1,203,249	1,020,469
Equity investments	0	0
Other assets, net	126,424	44,157
Total assets	1,543,316	1,283,784
Accounts payable		33,901
Accounts and notes payable	93,294
Accrued liabilities	75,405	21,873
Total current liabilities	168,699	55,774
Long-term debt	379,997	248,665
Deferred income taxes	1,712	1,392
Other liabilities	0	0
Total liabilities	550,408	305,831
Total Westlake Chemical Corporation stockholders' equity	992,908	977,953
Noncontrolling interests	0	0
Total equity	992,908	977,953
Total liabilities and equity	1,543,316	1,283,784
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	214,682	189,136	$ 132,371	$ 90,052
Marketable securities	0	0
Accounts receivable, net	136,839	113,321
Inventories	97,661	103,593
Prepaid expenses and other current assets	12,820	2,734
Deferred income taxes		1,950
Total current assets	462,002	410,734
Property, plant and equipment, net	420,947	415,701
Equity investments	471,900	469,915
Other assets, net	129,944	129,539
Total assets	1,484,793	1,425,889
Accounts payable		87,510
Accounts and notes payable	91,435
Accrued liabilities	94,545	88,142
Total current liabilities	185,980	175,652
Long-term debt	0	0
Deferred income taxes	48,596	47,941
Other liabilities	100,091	101,627
Total liabilities	334,667	325,220
Total Westlake Chemical Corporation stockholders' equity	851,853	804,616
Noncontrolling interests	298,273	296,053
Total equity	1,150,126	1,100,669
Total liabilities and equity	$ 1,484,793	$ 1,425,889