Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 1,942,616	$ 975,187
Cost of sales	1,575,473	719,602
Gross profit	367,143	255,585
Selling, general and administrative expenses	123,651	53,309
Transaction and integration-related costs	8,194	0
Income (loss) from operations	235,298	202,276
Interest expense	(39,776)	(6,685)
Other income (expense), net	5,071	2,645
Income (loss) before income taxes	(200,593)	(198,236)
Provision for (benefit from) income taxes	55,883	69,300
Equity in net income of subsidiaries	0	0
Net income	144,710	128,936
Net income attributable to noncontrolling interests	6,520	5,808
Net income attributable to Westlake Chemical Corporation	138,190	123,128
Comprehensive income attributable to Westlake Chemical Corporation	155,860	161,757
Westlake Chemical Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	0	0
Cost of sales	0	0
Gross profit	0	0
Selling, general and administrative expenses	778	607
Transaction and integration-related costs	0
Income (loss) from operations	(778)	(607)
Interest expense	(38,185)	(10,411)
Other income (expense), net	37,157	1,815
Income (loss) before income taxes	1,806	9,203
Provision for (benefit from) income taxes	(5,467)	(3,219)
Equity in net income of subsidiaries	134,529	129,112
Net income	138,190	123,128
Net income attributable to noncontrolling interests	0	0
Net income attributable to Westlake Chemical Corporation	138,190	123,128
Comprehensive income attributable to Westlake Chemical Corporation	155,860	161,757
100% Owned Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	1,579,725	761,736
Cost of sales	1,359,275	642,730
Gross profit	220,450	119,006
Selling, general and administrative expenses	92,260	36,996
Transaction and integration-related costs	8,132
Income (loss) from operations	120,058	82,010
Interest expense	(45,677)	(4,851)
Other income (expense), net	(255)	(825)
Income (loss) before income taxes	(74,126)	(76,334)
Provision for (benefit from) income taxes	53,372	62,199
Equity in net income of subsidiaries	0	0
Net income	20,754	14,135
Net income attributable to noncontrolling interests	0	0
Net income attributable to Westlake Chemical Corporation	20,754	14,135
Comprehensive income attributable to Westlake Chemical Corporation	4,635	14,341
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	736,085	569,824
Cost of sales	582,660	427,777
Gross profit	153,425	142,047
Selling, general and administrative expenses	37,345	21,174
Transaction and integration-related costs	62
Income (loss) from operations	116,018	120,873
Interest expense	(806)	0
Other income (expense), net	13,061	10,232
Income (loss) before income taxes	(128,273)	(131,105)
Provision for (benefit from) income taxes	7,978	10,320
Equity in net income of subsidiaries	0	0
Net income	120,295	120,785
Net income attributable to noncontrolling interests	6,520	5,808
Net income attributable to Westlake Chemical Corporation	113,775	114,977
Comprehensive income attributable to Westlake Chemical Corporation	122,243	149,462
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	(373,194)	(356,373)
Cost of sales	(366,462)	(350,905)
Gross profit	(6,732)	(5,468)
Selling, general and administrative expenses	(6,732)	(5,468)
Transaction and integration-related costs	0
Income (loss) from operations	0	0
Interest expense	44,892	8,577
Other income (expense), net	(44,892)	(8,577)
Income (loss) before income taxes	0	0
Provision for (benefit from) income taxes	0	0
Equity in net income of subsidiaries	(134,529)	(129,112)
Net income	(134,529)	(129,112)
Net income attributable to noncontrolling interests	0	0
Net income attributable to Westlake Chemical Corporation	(134,529)	(129,112)
Comprehensive income attributable to Westlake Chemical Corporation	$ (126,878)	$ (163,803)