Guarantor Disclosures (Condensed Consolidating Financial Information Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,198,468	$ 825,901	$ 758,939	$ 630,299
Accounts receivable, net	393,592	407,372
Inventories	371,537	490,777
Prepaid expenses and other current assets	14,472	12,495
Deferred income taxes	19,736	19,611
Total current assets	1,997,805	1,756,156
Property, plant and equipment, net	1,394,198	1,232,066
Equity investments	44,174	46,741
Restricted cash		96,283
Other assets, net	107,997	135,575
Total assets	3,544,174	3,266,821
Accounts payable	199,438	227,034
Accrued liabilities	163,369	137,561
Total current liabilities	362,807	364,595
Long-term debt	763,731	764,563
Deferred income taxes	335,394	330,791
Other liabilities	48,814	50,560
Stockholders' equity	2,033,428	1,756,312
Total liabilities and stockholders' equity	3,544,174	3,266,821
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	1,168,124	803,320	740,032	611,158
Accounts receivable, net	19,803
Prepaid expenses and other current assets	292	363
Deferred income taxes	430	430
Total current assets	1,188,649	804,113
Equity investments	2,910,021	2,597,598
Restricted cash		96,283
Other assets, net	17,622	17,650
Total assets	4,116,292	3,515,644
Accounts payable	1,314,329	1,005,529
Accrued liabilities	15,640	76
Total current liabilities	1,329,969	1,005,605
Long-term debt	752,842	753,674
Other liabilities	53	53
Stockholders' equity	2,033,428	1,756,312
Total liabilities and stockholders' equity	4,116,292	3,515,644
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	5,693	2,517	1,541	53
Accounts receivable, net	1,685,259	1,384,705
Inventories	357,780	478,229
Prepaid expenses and other current assets	11,253	10,332
Deferred income taxes	19,085	19,049
Total current assets	2,079,070	1,894,832
Property, plant and equipment, net	1,386,453	1,223,073
Equity investments	53,908	53,912
Other assets, net	106,350	132,968
Total assets	3,625,781	3,304,785
Accounts payable	179,772	210,476
Accrued liabilities	157,906	120,656
Total current liabilities	337,678	331,132
Long-term debt	10,889	10,889
Deferred income taxes	340,197	336,165
Other liabilities	48,704	50,458
Stockholders' equity	2,888,313	2,576,141
Total liabilities and stockholders' equity	3,625,781	3,304,785
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	24,651	20,064	17,366	19,088
Accounts receivable, net	5,480	949
Inventories	13,757	12,548
Prepaid expenses and other current assets	2,927	1,800
Deferred income taxes	221	132
Total current assets	47,036	35,493
Property, plant and equipment, net	7,745	8,993
Equity investments	33,244	35,650
Other assets, net	1,714	2,467
Total assets	89,739	82,603
Accounts payable	11,073	3,748
Accrued liabilities	1,037	2,392
Total current liabilities	12,110	6,140
Long-term debt	11,500	11,500
Deferred income taxes	1,386	636
Other liabilities	57	49
Stockholders' equity	64,686	64,278
Total liabilities and stockholders' equity	89,739	82,603
Eliminations
Condensed Financial Statements, Captions [Line Items]
Accounts receivable, net	(1,316,950)	(978,282)
Total current assets	(1,316,950)	(978,282)
Equity investments	(2,952,999)	(2,640,419)
Other assets, net	(17,689)	(17,510)
Total assets	(4,287,638)	(3,636,211)
Accounts payable	(1,305,736)	(992,719)
Accrued liabilities	(11,214)	14,437
Total current liabilities	(1,316,950)	(978,282)
Long-term debt	(11,500)	(11,500)
Deferred income taxes	(6,189)	(6,010)
Stockholders' equity	(2,952,999)	(2,640,419)
Total liabilities and stockholders' equity	$ (4,287,638)	$ (3,636,211)