Guarantor Disclosures (Condensed Consolidating Financial Information Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 380,519	$ 662,525	$ 961,925	$ 880,601
Marketable securities	0	520,144
Accounts receivable, net	1,070,501	508,532
Inventories	744,536	434,060
Prepaid expenses and other current assets	54,868	14,489
Restricted cash	169,320
Deferred income taxes	0	35,439
Total current assets	2,419,744	2,175,189
Property, plant and equipment, net	6,450,947	3,004,067
Other assets, net	2,026,358	390,029
Total assets	10,897,049	5,569,285
Accounts payable		235,329
Accounts and notes payable	503,388	235,329
Accrued liabilities	552,581	287,313
Term loan	148,681	0
Total current liabilities	1,204,650	522,642
Long-term debt, net	3,680,585	758,148
Deferred income taxes	1,607,084	575,603
Pension and other liabilities	580,593	150,961
Total liabilities	7,072,912	2,007,354
Total Westlake Chemical Corporation stockholders' equity	3,457,728	3,265,878
Noncontrolling interests	366,409	296,053
Total equity	3,824,137	3,561,931	3,519,838	3,201,888
Total liabilities and equity	10,897,049	5,569,285
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0	0	0
Marketable securities		0
Accounts receivable, net	(2,535,822)	(2,167,758)
Inventories	0	0
Prepaid expenses and other current assets	(13,394)	(2,879)
Restricted cash	0
Deferred income taxes		0
Total current assets	(2,549,216)	(2,170,637)
Property, plant and equipment, net	0	0
Other assets, net	(9,163,010)	(6,970,326)
Total assets	(11,712,226)	(9,140,963)
Accounts payable		(2,143,033)
Accounts and notes payable	(2,524,315)
Accrued liabilities	(24,901)	(27,604)
Term loan	0
Total current liabilities	(2,549,216)	(2,170,637)
Long-term debt, net	(2,881,906)	(733,516)
Deferred income taxes	(12,070)	(6,567)
Pension and other liabilities	0	0
Total liabilities	(5,443,192)	(2,910,720)
Total Westlake Chemical Corporation stockholders' equity	(6,269,034)	(6,230,243)
Noncontrolling interests	0	0
Total equity	(6,269,034)	(6,230,243)
Total liabilities and equity	(11,712,226)	(9,140,963)
Westlake Chemical Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	144,899	303,131	647,646	655,947
Marketable securities		520,144
Accounts receivable, net	1,457	10,943
Inventories	0	0
Prepaid expenses and other current assets	8,257	2,201
Restricted cash	0
Deferred income taxes		702
Total current assets	154,613	837,121
Property, plant and equipment, net	0	0
Other assets, net	9,074,810	5,003,096
Total assets	9,229,423	5,840,217
Accounts payable		1,817,963
Accounts and notes payable	2,172,989
Accrued liabilities	12,022	9,117
Term loan	0
Total current liabilities	2,185,011	1,827,080
Long-term debt, net	3,586,684	747,259
Deferred income taxes	0	0
Pension and other liabilities	0	0
Total liabilities	5,771,695	2,574,339
Total Westlake Chemical Corporation stockholders' equity	3,457,728	3,265,878
Noncontrolling interests	0	0
Total equity	3,457,728	3,265,878
Total liabilities and equity	9,229,423	5,840,217
100% Owned Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	1,884	6,818	5,435	3,047
Marketable securities		0
Accounts receivable, net	2,838,917	2,474,963
Inventories	329,233	287,114
Prepaid expenses and other current assets	16,264	10,186
Restricted cash	0
Deferred income taxes		28,325
Total current assets	3,186,298	2,807,406
Property, plant and equipment, net	1,538,148	1,476,642
Other assets, net	418,588	914,823
Total assets	5,143,034	5,198,871
Accounts payable		374,468
Accounts and notes payable	466,907
Accrued liabilities	162,645	163,167
Term loan	0
Total current liabilities	629,552	537,635
Long-term debt, net	775,995	744,405
Deferred income taxes	596,928	513,692
Pension and other liabilities	48,837	49,202
Total liabilities	2,051,312	1,844,934
Total Westlake Chemical Corporation stockholders' equity	3,091,722	3,353,937
Noncontrolling interests	0	0
Total equity	3,091,722	3,353,937
Total liabilities and equity	5,143,034	5,198,871
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	233,736	352,576	$ 308,844	$ 221,607
Marketable securities		0
Accounts receivable, net	765,949	190,384
Inventories	415,303	146,946
Prepaid expenses and other current assets	43,741	4,981
Restricted cash	169,320
Deferred income taxes		6,412
Total current assets	1,628,049	701,299
Property, plant and equipment, net	4,912,799	1,527,425
Other assets, net	1,695,970	1,442,436
Total assets	8,236,818	3,671,160
Accounts payable		185,931
Accounts and notes payable	387,807
Accrued liabilities	402,815	142,633
Term loan	148,681
Total current liabilities	939,303	328,564
Long-term debt, net	2,199,812	0
Deferred income taxes	1,022,226	68,478
Pension and other liabilities	531,756	101,759
Total liabilities	4,693,097	498,801
Total Westlake Chemical Corporation stockholders' equity	3,177,312	2,876,306
Noncontrolling interests	366,409	296,053
Total equity	3,543,721	3,172,359
Total liabilities and equity	$ 8,236,818	$ 3,671,160