Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 1,253,227	$ 1,004,165	$ 3,279,479	$ 2,807,859
Cost of sales	891,707	699,694	2,324,978	2,002,092
Gross profit	361,520	304,471	954,501	805,767
Selling, general and administrative expenses	54,759	37,869	132,897	109,883
Income from operations	306,761	266,602	821,604	695,884
Interest expense	(9,486)	(3,297)	(28,182)	(14,921)
Other (expense) income, net	(2,670)	(287)	4,440	3,137
Income before income taxes	294,605	263,018	797,862	684,100
Provision for (benefit from) income taxes	124,449	92,728	300,231	244,647
Equity in net income of subsidiaries	0	0	0	0
Net income	170,156	170,290	497,631	439,453	610,425
Net income attributable to noncontrolling interests	2,399	0	2,399	0
Net income to Westlake Chemical Corporation	167,757	170,290	495,232	439,453
Comprehensive income (loss)	131,456	171,095	461,415	439,372
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Net sales	0	0	0	0
Cost of sales	0	0	0	0
Gross profit	0	0	0	0
Selling, general and administrative expenses	399	514	1,474	1,576
Income from operations	(399)	(514)	(1,474)	(1,576)
Interest expense	(10,343)	(3,292)	(29,032)	(14,882)
Other (expense) income, net	2,138	3,585	14,488	7,490
Income before income taxes	(8,604)	(221)	(16,018)	(8,968)
Provision for (benefit from) income taxes	(3,088)	(70)	(5,686)	(3,202)
Equity in net income of subsidiaries	173,273	170,441	505,564	445,219
Net income	167,757		495,232	439,453
Net income attributable to noncontrolling interests	0		0
Net income to Westlake Chemical Corporation	167,757	170,290	495,232	439,453
Comprehensive income (loss)	131,456	171,095	461,415	439,372
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	1,026,282	844,081	2,809,844	2,407,341
Cost of sales	831,675	754,037	2,476,608	2,247,338
Gross profit	194,607	90,044	333,236	160,003
Selling, general and administrative expenses	36,445	29,323	123,050	84,152
Income from operations	158,162	60,721	210,186	75,851
Interest expense	(2)	(5)	(8)	(39)
Other (expense) income, net	(2,942)	(2,688)	(1,729)	(4,002)
Income before income taxes	155,218	58,028	208,449	71,810
Provision for (benefit from) income taxes	93,366	19,973	109,920	27,292
Equity in net income of subsidiaries	113,157	132,581	410,875	402,340
Net income	175,009		509,404	446,858
Net income attributable to noncontrolling interests	0		0
Net income to Westlake Chemical Corporation	175,009	170,636	509,404	446,858
Comprehensive income (loss)	175,137	170,764	509,787	447,490
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Net sales	392,008	540,133	1,476,157	1,565,809
Cost of sales	227,015	327,152	832,304	924,663
Gross profit	164,993	212,981	643,853	641,146
Selling, general and administrative expenses	8,014	6,391	21,957	19,326
Income from operations	156,979	206,590	621,896	621,820
Interest expense	(2,137)	(2,295)	(9,833)	(4,893)
Other (expense) income, net	486	1,162	3,135	6,422
Income before income taxes	155,328	205,457	615,198	623,349
Provision for (benefit from) income taxes	36,309	72,876	198,461	221,009
Equity in net income of subsidiaries	0	0	0	0
Net income	119,019		416,737	402,340
Net income attributable to noncontrolling interests	0		0
Net income to Westlake Chemical Corporation	119,019	132,581	416,737	402,340
Comprehensive income (loss)	119,019	132,581	416,737	402,340
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	208,313	13,337	229,183	37,561
Cost of sales	202,110	11,891	221,233	32,943
Gross profit	6,203	1,446	7,950	4,618
Selling, general and administrative expenses	14,184	1,641	16,954	4,829
Income from operations	(7,981)	(195)	(9,004)	(211)
Interest expense	(39)	0	(39)	0
Other (expense) income, net	683	(51)	(724)	(1,880)
Income before income taxes	(7,337)	(246)	(9,767)	(2,091)
Provision for (benefit from) income taxes	(2,138)	(51)	(2,464)	(452)
Equity in net income of subsidiaries	5,862	0	5,862	0
Net income	663		(1,441)	(1,639)
Net income attributable to noncontrolling interests	2,399		2,399
Net income to Westlake Chemical Corporation	(1,736)	(195)	(3,840)	(1,639)
Comprehensive income (loss)	(39,528)	351	(41,722)	(2,483)
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net sales	(373,376)	(393,386)	(1,235,705)	(1,202,852)
Cost of sales	(369,093)	(393,386)	(1,205,167)	(1,202,852)
Gross profit	(4,283)	0	(30,538)	0
Selling, general and administrative expenses	(4,283)	0	(30,538)	0
Income from operations	0	0	0	0
Interest expense	3,035	2,295	10,730	4,893
Other (expense) income, net	(3,035)	(2,295)	(10,730)	(4,893)
Income before income taxes	0	0	0	0
Provision for (benefit from) income taxes	0	0	0	0
Equity in net income of subsidiaries	(292,292)	(303,022)	(922,301)	(847,559)
Net income	(292,292)		(922,301)	(847,559)
Net income attributable to noncontrolling interests	0		0
Net income to Westlake Chemical Corporation	(292,292)	(303,022)	(922,301)	(847,559)
Comprehensive income (loss)	$ (254,628)	$ (303,696)	$ (884,802)	$ (847,347)