Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 2,108,889	$ 1,279,028	$ 6,030,666	$ 3,340,276
Cost of sales	1,610,837	1,076,895	4,759,637	2,641,192
Gross profit	498,052	202,133	1,271,029	699,084
Selling, general and administrative expenses	125,642	72,729	379,919	179,757
Transaction and integration-related costs	6,663	82,841	22,949	90,550
Income (loss) from operations	365,747	46,563	868,161	428,777
Interest expense	(40,036)	(24,366)	(118,784)	(36,966)
Other income (expense), net	2,058	41,265	6,591	52,091
Income before income taxes	327,769	63,462	755,968	443,902
Provision for (benefit from) income taxes	108,619	(6,552)	232,690	129,332
Equity in net income of subsidiaries	0	0	0	0
Net income	219,150	70,014	523,278	314,570
Net income attributable to noncontrolling interests	8,318	4,352	21,429	14,656
Net income attributable to Westlake Chemical Corporation	210,832	65,662	501,849	299,914
Comprehensive income attributable to Westlake Chemical Corporation	254,400	39,637	613,350	321,080
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	(432,733)	(317,892)	(1,227,878)	(961,567)
Cost of sales	(426,100)	(312,763)	(1,207,567)	(945,967)
Gross profit	(6,633)	(5,129)	(20,311)	(15,600)
Selling, general and administrative expenses	(6,633)	(5,129)	(20,311)	(15,600)
Transaction and integration-related costs	0	0	0	0
Income (loss) from operations	0	0	0	0
Interest expense	44,791	20,879	135,043	47,009
Other income (expense), net	(44,791)	(20,879)	(135,043)	(47,009)
Income before income taxes	0	0	0	0
Provision for (benefit from) income taxes	0	0	0	0
Equity in net income of subsidiaries	(212,989)	(52,391)	(505,981)	(297,715)
Net income	(212,989)	(52,391)	(505,981)	(297,715)
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	(212,989)	(52,391)	(505,981)	(297,715)
Comprehensive income attributable to Westlake Chemical Corporation	(256,615)	(40,015)	(404,443)	(318,214)
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	1,509	2,092	2,429	3,648
Transaction and integration-related costs	0	0	0	0
Income (loss) from operations	(1,509)	(2,092)	(2,429)	(3,648)
Interest expense	(38,811)	(22,130)	(115,156)	(43,228)
Other income (expense), net	37,563	35,405	112,002	40,807
Income before income taxes	(2,757)	11,183	(5,583)	(6,069)
Provision for (benefit from) income taxes	(599)	(2,088)	(1,451)	(8,268)
Equity in net income of subsidiaries	212,989	52,391	505,981	297,715
Net income	210,831	65,662	501,849	299,914
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	210,831	65,662	501,849	299,914
Comprehensive income attributable to Westlake Chemical Corporation	254,400	39,636	613,350	321,079
100% Owned Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	1,704,086	984,937	4,880,682	2,567,232
Cost of sales	1,371,813	892,198	4,077,633	2,233,395
Gross profit	332,273	92,739	803,049	333,837
Selling, general and administrative expenses	93,149	47,952	281,412	121,261
Transaction and integration-related costs	6,387	82,687	22,611	90,396
Income (loss) from operations	232,737	(37,900)	499,026	122,180
Interest expense	(44,381)	(22,207)	(133,048)	(39,693)
Other income (expense), net	2,517	(15,189)	2,944	(22,291)
Income before income taxes	190,873	(75,296)	368,922	60,196
Provision for (benefit from) income taxes	92,597	(11,080)	198,054	106,792
Equity in net income of subsidiaries	0	0	0	0
Net income	98,276	(64,216)	170,868	(46,596)
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	98,276	(64,216)	170,868	(46,596)
Comprehensive income attributable to Westlake Chemical Corporation	98,455	(64,113)	171,413	(46,187)
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	837,536	611,983	2,377,862	1,734,611
Cost of sales	665,124	497,460	1,889,571	1,353,764
Gross profit	172,412	114,523	488,291	380,847
Selling, general and administrative expenses	37,617	27,814	116,389	70,448
Transaction and integration-related costs	276	154	338	154
Income (loss) from operations	134,519	86,555	371,564	310,245
Interest expense	(1,635)	(908)	(5,623)	(1,054)
Other income (expense), net	6,769	41,928	26,688	80,584
Income before income taxes	139,653	127,575	392,629	389,775
Provision for (benefit from) income taxes	16,621	6,616	36,087	30,808
Equity in net income of subsidiaries	0	0	0	0
Net income	123,032	120,959	356,542	358,967
Net income attributable to noncontrolling interests	8,318	4,352	21,429	14,656
Net income attributable to Westlake Chemical Corporation	114,714	116,607	335,113	344,311
Comprehensive income attributable to Westlake Chemical Corporation	$ 158,160	$ 104,129	$ 233,030	$ 364,402