Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 1,086,061	$ 1,185,002	$ 2,061,248	$ 2,288,533
Cost of sales	844,695	831,821	1,564,297	1,650,806
Gross profit	241,366	353,181	496,951	637,727
Selling, general and administrative expenses	61,428	57,807	114,737	113,073
Income (loss) from operations	179,938	295,374	382,214	524,654
Interest expense	(5,915)	(8,958)	(12,600)	(18,549)
Other income, net	8,181	22,058	10,826	31,154
(Loss) income before income taxes	182,204	308,474	380,440	537,259
Provision for (benefit from) income taxes	66,584	98,413	135,884	176,791
Equity in net income of subsidiaries	0	0	0	0
Net income	115,620	210,061	244,556	360,468
Net income attributable to noncontrolling interests	4,496	4,966	10,304	9,031
Net income attributable to Westlake Chemical Corporation	111,124	205,095	234,252	351,437
Comprehensive income attributable to Westlake Chemical Corporation	119,686	222,833	281,443	310,946
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	950	399	1,557	812
Income (loss) from operations	(950)	(399)	(1,557)	(812)
Interest expense	(10,688)	(10,569)	(21,099)	(21,321)
Other income, net	3,587	9,776	5,402	16,387
(Loss) income before income taxes	(8,051)	(1,192)	(17,254)	(5,746)
Provision for (benefit from) income taxes	(2,960)	(399)	(6,182)	(1,976)
Equity in net income of subsidiaries	116,215	205,888	245,324	355,207
Net income	111,124	205,095	234,252	351,437
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	111,124	205,095	234,252	351,437
Comprehensive income attributable to Westlake Chemical Corporation	119,686	222,833	281,443	310,946
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	845,088	990,434	1,629,152	1,901,365
Cost of sales	720,774	750,892	1,386,241	1,485,728
Gross profit	124,314	239,542	242,911	415,637
Selling, general and administrative expenses	48,331	42,682	88,959	86,366
Income (loss) from operations	75,983	196,860	153,952	329,271
Interest expense	(13)	(4)	(16)	(5)
Other income, net	4,900	(9,371)	11,343	(6,544)
(Loss) income before income taxes	80,870	187,485	165,279	322,722
Provision for (benefit from) income taxes	62,396	97,218	129,252	175,170
Equity in net income of subsidiaries	71,849	76,799	162,536	156,690
Net income	90,323	167,066	198,563	304,242
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	90,323	167,066	198,563	304,242
Comprehensive income attributable to Westlake Chemical Corporation	102,001	167,206	222,127	304,620
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Net sales	210,841	251,705	463,445	510,096
Cost of sales	122,460	157,177	264,650	319,341
Gross profit	88,381	94,528	198,795	190,755
Selling, general and administrative expenses	5,174	5,191	10,452	10,237
Income (loss) from operations	83,207	89,337	188,343	180,518
Interest expense	(221)	(856)	(472)	(2,232)
Other income, net	159	34	243	39
(Loss) income before income taxes	83,145	88,515	188,114	178,325
Provision for (benefit from) income taxes	297	(41)	696	426
Equity in net income of subsidiaries	0	0	0	0
Net income	82,848	88,556	187,418	177,899
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	82,848	88,556	187,418	177,899
Comprehensive income attributable to Westlake Chemical Corporation	82,848	88,556	187,418	177,899
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	289,520	250,365	552,434	496,007
Cost of sales	255,846	226,283	486,718	454,553
Gross profit	33,674	24,082	65,716	41,454
Selling, general and administrative expenses	11,976	14,506	24,240	25,777
Income (loss) from operations	21,698	9,576	41,476	15,677
Interest expense	(50)	(52)	(128)	(94)
Other income, net	4,592	24,142	2,953	26,375
(Loss) income before income taxes	26,240	33,666	44,301	41,958
Provision for (benefit from) income taxes	6,851	1,635	12,118	3,171
Equity in net income of subsidiaries	10,999	11,757	24,882	21,209
Net income	30,388	43,788	57,065	59,996
Net income attributable to noncontrolling interests	4,496	4,966	10,304	9,031
Net income attributable to Westlake Chemical Corporation	25,892	38,822	46,761	50,965
Comprehensive income attributable to Westlake Chemical Corporation	12,392	56,879	56,066	9,513
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	(259,388)	(307,502)	(583,783)	(618,935)
Cost of sales	(254,385)	(302,531)	(573,312)	(608,816)
Gross profit	(5,003)	(4,971)	(10,471)	(10,119)
Selling, general and administrative expenses	(5,003)	(4,971)	(10,471)	(10,119)
Income (loss) from operations	0	0	0	0
Interest expense	5,057	2,523	9,115	5,103
Other income, net	(5,057)	(2,523)	(9,115)	(5,103)
(Loss) income before income taxes	0	0	0	0
Provision for (benefit from) income taxes	0	0	0	0
Equity in net income of subsidiaries	(199,063)	(294,444)	(432,742)	(533,106)
Net income	(199,063)	(294,444)	(432,742)	(533,106)
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	(199,063)	(294,444)	(432,742)	(533,106)
Comprehensive income attributable to Westlake Chemical Corporation	$ (197,241)	$ (312,641)	$ (465,611)	$ (492,032)