Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 1,103,531	$ 1,027,676
Cost of sales	818,985	740,666
Gross profit	284,546	287,010
Selling, general and administrative expenses	55,266	38,955
Income from operations	229,280	248,055
Interest expense	(9,591)	(9,157)
Other income, net	9,096	2,509
Income before income taxes	228,785	241,407
Provision for (benefit from) income taxes	78,378	83,375
Equity in net income of subsidiaries	0	0
Net income	150,407	158,032
Net income attributable to noncontrolling interests	4,065	0
Net income attributable to Westlake Chemical Corporation	146,342	158,032
Comprehensive income (loss) attributable to Westlake Chemical Corporation	88,113	158,866
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Net sales	0	0
Cost of sales	0	0
Gross profit	0	0
Selling, general and administrative expenses	413	546
Income from operations	(413)	(546)
Interest expense	(10,752)	(8,947)
Other income, net	6,612	5,006
Income before income taxes	(4,553)	(4,487)
Provision for (benefit from) income taxes	(1,578)	(1,558)
Equity in net income of subsidiaries	149,317	160,961
Net income	146,342	158,032
Net income attributable to noncontrolling interests	0
Net income attributable to Westlake Chemical Corporation	146,342	158,032
Comprehensive income (loss) attributable to Westlake Chemical Corporation	88,113	158,866
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	903,492	844,342
Cost of sales	727,399	790,577
Gross profit	176,093	53,765
Selling, general and administrative expenses	43,684	29,285
Income from operations	132,409	24,480
Interest expense	(1)	(210)
Other income, net	2,827	456
Income before income taxes	135,235	24,726
Provision for (benefit from) income taxes	77,999	6,787
Equity in net income of subsidiaries	79,891	143,874
Net income	137,127	161,813
Net income attributable to noncontrolling interests	0
Net income attributable to Westlake Chemical Corporation	137,127	161,813
Comprehensive income (loss) attributable to Westlake Chemical Corporation	137,365	161,948
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Net sales	258,391	560,014
Cost of sales	162,164	327,700
Gross profit	96,227	232,314
Selling, general and administrative expenses	5,046	7,778
Income from operations	91,181	224,536
Interest expense	(1,376)	(3,591)
Other income, net	5	1,252
Income before income taxes	89,810	222,197
Provision for (benefit from) income taxes	467	78,323
Equity in net income of subsidiaries	0	0
Net income	89,343	143,874
Net income attributable to noncontrolling interests	0
Net income attributable to Westlake Chemical Corporation	89,343	143,874
Comprehensive income (loss) attributable to Westlake Chemical Corporation	89,343	143,874
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	245,643	9,117
Cost of sales	228,269	8,186
Gross profit	17,374	931
Selling, general and administrative expenses	11,271	1,346
Income from operations	6,103	(415)
Interest expense	(42)	0
Other income, net	2,232	(614)
Income before income taxes	8,293	(1,029)
Provision for (benefit from) income taxes	1,490	(177)
Equity in net income of subsidiaries	9,452	0
Net income	16,255	(852)
Net income attributable to noncontrolling interests	4,065
Net income attributable to Westlake Chemical Corporation	12,190	(852)
Comprehensive income (loss) attributable to Westlake Chemical Corporation	(47,319)	(1,750)
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net sales	(303,995)	(385,797)
Cost of sales	(298,847)	(385,797)
Gross profit	(5,148)	0
Selling, general and administrative expenses	(5,148)	0
Income from operations	0	0
Interest expense	2,580	3,591
Other income, net	(2,580)	(3,591)
Income before income taxes	0	0
Provision for (benefit from) income taxes	0	0
Equity in net income of subsidiaries	(238,660)	(304,835)
Net income	(238,660)	(304,835)
Net income attributable to noncontrolling interests	0
Net income attributable to Westlake Chemical Corporation	(238,660)	(304,835)
Comprehensive income (loss) attributable to Westlake Chemical Corporation	$ (179,389)	$ (304,072)