Guarantor Disclosures (Condensed Consolidating Financial Information Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 591,556	$ 790,078	$ 1,198,468	$ 825,901
Marketable Securities, Current	125,597	124,873
Accounts receivable, net	433,025	400,159
Inventories	451,571	399,298
Prepaid expenses and other current assets	18,809	14,700
Deferred income taxes	22,293	22,305
Total current assets	1,642,851	1,751,413
Property, plant and equipment, net	1,952,918	1,510,048
Equity investments	65,488	43,736
Other assets, net	262,192	106,999
Total assets	3,923,449	3,412,196
Accounts payable	258,067	217,050
Accrued liabilities	174,619	181,460
Total current liabilities	432,686	398,510
Long-term debt	763,849	763,761
Deferred income taxes	410,166	326,290
Other liabilities	51,691	51,379
Stockholders' equity	2,265,057	1,872,256
Total liabilities and stockholders' equity	3,923,449	3,412,196
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	560,261	753,881	1,168,124	803,320
Marketable Securities, Current	125,597	124,873
Accounts receivable, net	5,373	7,933
Inventories	0	0
Prepaid expenses and other current assets	468	389
Deferred income taxes	431	431
Total current assets	692,130	887,507
Property, plant and equipment, net	0	0
Equity investments	2,635,954	3,018,926
Other assets, net	16,969	17,033
Total assets	3,345,053	3,923,466
Accounts payable	311,357	1,285,530
Accrued liabilities	15,679	12,808
Total current liabilities	327,036	1,298,338
Long-term debt	752,960	752,872
Deferred income taxes	0	0
Other liabilities	0	0
Stockholders' equity	2,265,057	1,872,256
Total liabilities and stockholders' equity	3,345,053	3,923,466
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	4,494	6,973	5,693	2,517
Marketable Securities, Current	0	0
Accounts receivable, net	694,473	1,675,274
Inventories	435,540	385,140
Prepaid expenses and other current assets	15,931	11,386
Deferred income taxes	21,744	21,581
Total current assets	1,172,182	2,100,354
Property, plant and equipment, net	1,945,405	1,502,902
Equity investments	98,823	65,448
Other assets, net	251,703	94,678
Total assets	3,468,113	3,763,382
Accounts payable	220,106	192,443
Accrued liabilities	151,654	178,915
Total current liabilities	371,760	371,358
Long-term debt	10,889	10,889
Deferred income taxes	416,404	331,320
Other liabilities	51,640	51,312
Stockholders' equity	2,617,420	2,998,503
Total liabilities and stockholders' equity	3,468,113	3,763,382
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	26,801	29,224	24,651	20,064
Marketable Securities, Current	0	0
Accounts receivable, net	5,489	2,959
Inventories	16,031	14,158
Prepaid expenses and other current assets	2,410	2,925
Deferred income taxes	118	293
Total current assets	50,849	49,559
Property, plant and equipment, net	7,513	7,146
Equity investments	31,634	32,923
Other assets, net	506	1,252
Total assets	90,502	90,880
Accounts payable	4,322	13,969
Accrued liabilities	1,878	852
Total current liabilities	6,200	14,821
Long-term debt	0	0
Deferred income taxes	748	934
Other liabilities	51	67
Stockholders' equity	83,503	75,058
Total liabilities and stockholders' equity	90,502	90,880
Eliminations
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0	0	0
Marketable Securities, Current	0	0
Accounts receivable, net	(272,310)	(1,286,007)
Inventories	0	0
Prepaid expenses and other current assets	0	0
Deferred income taxes	0	0
Total current assets	(272,310)	(1,286,007)
Property, plant and equipment, net	0	0
Equity investments	(2,700,923)	(3,073,561)
Other assets, net	(6,986)	(5,964)
Total assets	(2,980,219)	(4,365,532)
Accounts payable	(277,718)	(1,274,892)
Accrued liabilities	5,408	(11,115)
Total current liabilities	(272,310)	(1,286,007)
Long-term debt	0	0
Deferred income taxes	(6,986)	(5,964)
Other liabilities	0	0
Stockholders' equity	(2,700,923)	(3,073,561)
Total liabilities and stockholders' equity	$ (2,980,219)	$ (4,365,532)