Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 1,188,037	$ 1,253,227	$ 3,476,570	$ 3,279,479
Cost of sales	876,761	891,707	2,527,567	2,324,978
Gross profit	311,276	361,520	949,003	954,501
Selling, general and administrative expenses	57,248	54,759	170,321	132,897
Income from operations	254,028	306,761	778,682	821,604
Interest expense	(8,211)	(9,486)	(26,760)	(28,182)
Other income, net	2,636	(2,670)	33,790	4,440
Income before income taxes	248,453	294,605	785,712	797,862
Provision for (benefit from) income taxes	60,033	124,449	236,824	300,231
Equity in net income of subsidiaries	0	0	0	0
Net income	188,420	170,156	548,888	497,631
Net income attributable to noncontrolling interests	4,816	2,399	13,847	2,399
Net income attributable to Westlake Chemical Corporation	183,604	167,757	535,041	495,232
Comprehensive income (loss) attributable to Westlake Chemical Corporation	181,663	131,456	492,609	461,415
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	804	399	1,617	1,474
Income from operations	(804)	(399)	(1,617)	(1,474)
Interest expense	(10,405)	(10,343)	(31,726)	(29,032)
Other income, net	1,239	2,138	17,627	14,488
Income before income taxes	(9,970)	(8,604)	(15,716)	(16,018)
Provision for (benefit from) income taxes	(3,249)	(3,088)	(5,226)	(5,686)
Equity in net income of subsidiaries	190,325	173,273	545,531	505,564
Net income	183,604	167,757	535,041	495,232
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	183,604	167,757	535,041	495,232
Comprehensive income (loss) attributable to Westlake Chemical Corporation	181,663	131,456	492,609	461,415
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	961,036	1,026,282	2,862,400	2,809,844
Cost of sales	774,726	831,675	2,260,454	2,476,608
Gross profit	186,310	194,607	601,946	333,236
Selling, general and administrative expenses	41,429	36,445	127,794	123,050
Income from operations	144,881	158,162	474,152	210,186
Interest expense	(3)	(2)	(8)	(8)
Other income, net	3,971	(2,942)	(2,574)	(1,729)
Income before income taxes	148,849	155,218	471,570	208,449
Provision for (benefit from) income taxes	56,372	93,366	231,542	109,920
Equity in net income of subsidiaries	76,945	113,157	233,635	410,875
Net income	169,422	175,009	473,663	509,404
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	169,422	175,009	473,663	509,404
Comprehensive income (loss) attributable to Westlake Chemical Corporation	169,673	175,137	474,292	509,787
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Net sales	248,619	392,008	758,715	1,476,157
Cost of sales	154,474	227,015	473,815	832,304
Gross profit	94,145	164,993	284,900	643,853
Selling, general and administrative expenses	4,941	8,014	15,178	21,957
Income from operations	89,204	156,979	269,722	621,896
Interest expense	(217)	(2,137)	(2,449)	(9,833)
Other income, net	(124)	486	(85)	3,135
Income before income taxes	88,863	155,328	267,188	615,198
Provision for (benefit from) income taxes	141	36,309	567	198,461
Equity in net income of subsidiaries	0	0	0	0
Net income	88,722	119,019	266,621	416,737
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	88,722	119,019	266,621	416,737
Comprehensive income (loss) attributable to Westlake Chemical Corporation	88,722	119,019	266,621	416,737
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	288,211	208,313	784,219	229,183
Cost of sales	252,618	202,110	707,171	221,233
Gross profit	35,593	6,203	77,048	7,950
Selling, general and administrative expenses	14,846	14,184	40,623	16,954
Income from operations	20,747	(7,981)	36,425	(9,004)
Interest expense	(95)	(39)	(190)	(39)
Other income, net	59	683	26,435	(724)
Income before income taxes	20,711	(7,337)	62,670	(9,767)
Provision for (benefit from) income taxes	6,769	(2,138)	9,941	(2,464)
Equity in net income of subsidiaries	11,777	5,862	32,986	5,862
Net income	25,719	663	85,715	(1,441)
Net income attributable to noncontrolling interests	4,816	2,399	13,847	2,399
Net income attributable to Westlake Chemical Corporation	20,903	(1,736)	71,868	(3,840)
Comprehensive income (loss) attributable to Westlake Chemical Corporation	19,170	(39,528)	28,683	(41,722)
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net sales	(309,829)	(373,376)	(928,764)	(1,235,705)
Cost of sales	(305,057)	(369,093)	(913,873)	(1,205,167)
Gross profit	(4,772)	(4,283)	(14,891)	(30,538)
Selling, general and administrative expenses	(4,772)	(4,283)	(14,891)	(30,538)
Income from operations	0	0	0	0
Interest expense	2,509	3,035	7,613	10,730
Other income, net	(2,509)	(3,035)	(7,613)	(10,730)
Income before income taxes	0	0	0	0
Provision for (benefit from) income taxes	0	0	0	0
Equity in net income of subsidiaries	(279,047)	(292,292)	(812,152)	(922,301)
Net income	(279,047)	(292,292)	(812,152)	(922,301)
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	(279,047)	(292,292)	(812,152)	(922,301)
Comprehensive income (loss) attributable to Westlake Chemical Corporation	$ (277,565)	$ (254,628)	$ (769,596)	$ (884,802)