Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 1,279,028	$ 1,188,037	$ 3,340,276	$ 3,476,570
Cost of sales	1,076,895	876,761	2,641,192	2,527,567
Gross profit	202,133	311,276	699,084	949,003
Selling, general and administrative expenses	72,729	57,248	179,757	170,321
Transaction and integration-related costs	82,841	0	90,550	0
Income from operations	46,563	254,028	428,777	778,682
Interest expense	(24,366)	(8,211)	(36,966)	(26,760)
Other income, net	41,265	2,636	52,091	33,790
Income before income taxes	63,462	248,453	443,902	785,712
(Benefit from) provision for income taxes	(6,552)	60,033	129,332	236,824
Equity in net income of subsidiaries	0	0	0	0
Net income	70,014	188,420	314,570	548,888
Net income attributable to noncontrolling interests	4,352	4,816	14,656	13,847
Net income attributable to Westlake Chemical Corporation	65,662	183,604	299,914	535,041
Comprehensive income attributable to Westlake Chemical Corporation	39,637	181,663	321,080	492,609
Westlake Chemical Corporation [Member]
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	2,092	804	3,648	1,617
Transaction and integration-related costs	0		0
Income from operations	(2,092)	(804)	(3,648)	(1,617)
Interest expense	(22,130)	(10,405)	(43,228)	(31,726)
Other income, net	35,405	1,239	40,807	17,627
Income before income taxes	11,183	(9,970)	(6,069)	(15,716)
(Benefit from) provision for income taxes	(2,088)	(3,249)	(8,268)	(5,226)
Equity in net income of subsidiaries	52,391	190,325	297,715	545,531
Net income	65,662	183,604	299,914	535,041
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	65,662	183,604	299,914	535,041
Comprehensive income attributable to Westlake Chemical Corporation	39,637	181,663	321,080	492,609
100% Owned Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	775,474	901,006	2,357,769	2,677,773
Cost of sales	677,085	712,681	2,018,282	2,078,730
Gross profit	98,389	188,325	339,487	599,043
Selling, general and administrative expenses	31,180	37,156	104,488	115,400
Transaction and integration-related costs	35,379		43,088
Income from operations	31,830	151,169	191,911	483,643
Interest expense	(10,247)	(5,711)	(19,051)	(18,353)
Other income, net	(8,622)	203	(12,057)	(4,743)
Income before income taxes	12,961	145,661	160,803	460,547
(Benefit from) provision for income taxes	18,987	53,131	136,856	222,743
Equity in net income of subsidiaries	0	0	0	0
Net income	(6,026)	92,530	23,947	237,804
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	(6,026)	92,530	23,947	237,804
Comprehensive income attributable to Westlake Chemical Corporation	(5,923)	92,781	24,356	238,433
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	823,238	596,860	1,945,866	1,727,561
Cost of sales	714,365	469,137	1,570,669	1,362,710
Gross profit	108,873	127,723	375,197	364,851
Selling, general and administrative expenses	44,586	24,060	87,221	68,195
Transaction and integration-related costs	47,462		47,462
Income from operations	16,825	103,663	240,514	296,656
Interest expense	(9,117)	0	(9,117)	0
Other income, net	31,610	9,099	57,771	44,225
Income before income taxes	39,318	112,762	289,168	340,881
(Benefit from) provision for income taxes	(23,451)	10,151	744	19,307
Equity in net income of subsidiaries	0	0	0	0
Net income	62,769	102,611	288,424	321,574
Net income attributable to noncontrolling interests	4,352	4,816	14,656	13,847
Net income attributable to Westlake Chemical Corporation	58,417	97,795	273,768	307,727
Comprehensive income attributable to Westlake Chemical Corporation	45,945	96,062	293,859	264,542
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	(319,684)	(309,829)	(963,359)	(928,764)
Cost of sales	(314,555)	(305,057)	(947,759)	(913,873)
Gross profit	(5,129)	(4,772)	(15,600)	(14,891)
Selling, general and administrative expenses	(5,129)	(4,772)	(15,600)	(14,891)
Transaction and integration-related costs	0		0
Income from operations	0	0	0	0
Interest expense	17,128	7,905	34,430	23,319
Other income, net	(17,128)	(7,905)	(34,430)	(23,319)
Income before income taxes	0	0	0	0
(Benefit from) provision for income taxes	0	0	0	0
Equity in net income of subsidiaries	(52,391)	(190,325)	(297,715)	(545,531)
Net income	(52,391)	(190,325)	(297,715)	(545,531)
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	(52,391)	(190,325)	(297,715)	(545,531)
Comprehensive income attributable to Westlake Chemical Corporation	$ (40,022)	$ (188,843)	$ (318,215)	$ (502,975)