Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 1,185,002	$ 998,576	$ 2,288,533	$ 2,026,252
Cost of sales	831,821	692,605	1,650,806	1,433,271
Gross profit	353,181	305,971	637,727	592,981
Selling, general and administrative expenses	57,807	39,183	113,073	78,138
Income from operations	295,374	266,788	524,654	514,843
Interest expense	(8,958)	(9,539)	(18,549)	(18,696)
Other income, net	22,058	4,601	31,154	7,110
Income before income taxes	308,474	261,850	537,259	503,257
Provision for (benefit from) income taxes	98,413	92,407	176,791	175,782
Equity in net income of subsidiaries	0	0	0	0
Net income	210,061	169,443	360,468	327,475
Net income attributable to noncontrolling interests	4,966	0	9,031	0
Net income attributable to Westlake Chemical Corporation	205,095	169,443	351,437	327,475
Comprehensive income (loss) attributable to Westlake Chemical Corporation	222,833	171,093	310,946	329,959
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	529	812	1,075
Income from operations	(399)	(529)	(812)	(1,075)
Interest expense	(10,569)	(9,535)	(21,321)	(18,690)
Other income, net	9,776	7,137	16,387	12,351
Income before income taxes	(1,192)	(2,927)	(5,746)	(7,414)
Provision for (benefit from) income taxes	(399)	(1,039)	(1,976)	(2,597)
Equity in net income of subsidiaries	205,888	171,331	355,207	332,292
Net income	205,095		351,437	327,475
Net income attributable to noncontrolling interests	0		0
Net income attributable to Westlake Chemical Corporation	205,095	169,443	351,437	327,475
Comprehensive income (loss) attributable to Westlake Chemical Corporation	222,833	171,093	310,946	329,959
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	990,434	879,842	1,901,365	1,724,184
Cost of sales	750,892	821,234	1,485,728	1,611,811
Gross profit	239,542	58,608	415,637	112,373
Selling, general and administrative expenses	42,682	31,066	86,366	60,351
Income from operations	196,860	27,542	329,271	52,022
Interest expense	(4)	(4)	(5)	(6)
Other income, net	(9,371)	965	(6,544)	1,213
Income before income taxes	187,485	28,503	322,722	53,229
Provision for (benefit from) income taxes	97,218	9,766	175,170	16,553
Equity in net income of subsidiaries	76,799	153,844	156,690	297,718
Net income	167,066		304,242	334,394
Net income attributable to noncontrolling interests	0		0
Net income attributable to Westlake Chemical Corporation	167,066	172,581	304,242	334,394
Comprehensive income (loss) attributable to Westlake Chemical Corporation	167,206	172,701	304,620	334,649
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Net sales	251,705	524,135	510,096	1,084,149
Cost of sales	157,177	277,589	319,341	605,289
Gross profit	94,528	246,546	190,755	478,860
Selling, general and administrative expenses	5,191	6,165	10,237	13,943
Income from operations	89,337	240,381	180,518	464,917
Interest expense	(856)	(4,105)	(2,232)	(7,696)
Other income, net	34	1,397	39	2,649
Income before income taxes	88,515	237,673	178,325	459,870
Provision for (benefit from) income taxes	(41)	83,829	426	162,152
Equity in net income of subsidiaries	0	0	0	0
Net income	88,556		177,899	297,718
Net income attributable to noncontrolling interests	0		0
Net income attributable to Westlake Chemical Corporation	88,556	153,844	177,899	297,718
Comprehensive income (loss) attributable to Westlake Chemical Corporation	88,556	153,844	177,899	297,718
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	250,365	11,753	496,007	20,870
Cost of sales	226,283	10,936	454,553	19,122
Gross profit	24,082	817	41,454	1,748
Selling, general and administrative expenses	14,506	1,423	25,777	2,769
Income from operations	9,576	(606)	15,677	(1,021)
Interest expense	(52)	0	(94)	0
Other income, net	24,142	(793)	26,375	(1,407)
Income before income taxes	33,666	(1,399)	41,958	(2,428)
Provision for (benefit from) income taxes	1,635	(149)	3,171	(326)
Equity in net income of subsidiaries	11,757	0	21,209	0
Net income	43,788		59,996	(2,102)
Net income attributable to noncontrolling interests	4,966		9,031
Net income attributable to Westlake Chemical Corporation	38,822	(1,250)	50,965	(2,102)
Comprehensive income (loss) attributable to Westlake Chemical Corporation	56,879	(442)	9,513	(2,192)
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net sales	(307,502)	(417,154)	(618,935)	(802,951)
Cost of sales	(302,531)	(417,154)	(608,816)	(802,951)
Gross profit	(4,971)	0	(10,119)	0
Selling, general and administrative expenses	(4,971)	0	(10,119)	0
Income from operations	0	0	0	0
Interest expense	2,523	4,105	5,103	7,696
Other income, net	(2,523)	(4,105)	(5,103)	(7,696)
Income before income taxes	0	0	0	0
Provision for (benefit from) income taxes	0	0	0	0
Equity in net income of subsidiaries	(294,444)	(325,175)	(533,106)	(630,010)
Net income	(294,444)		(533,106)	(630,010)
Net income attributable to noncontrolling interests	0		0
Net income attributable to Westlake Chemical Corporation	(294,444)	(325,175)	(533,106)	(630,010)
Comprehensive income (loss) attributable to Westlake Chemical Corporation	$ (312,641)	$ (326,103)	$ (492,032)	$ (630,175)