Guarantor Disclosures (Condensed Consolidating Financial Information Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 678,233	$ 459,453	$ 380,519	$ 662,525
Accounts receivable, net	1,142,979	938,743
Inventories	834,835	801,100
Prepaid expenses and other current assets	34,860	48,493
Restricted cash	8,626	160,527
Total current assets	2,699,533	2,408,316
Property, plant and equipment, net	6,343,637	6,420,062
Goodwill	1,011,342	946,553
Customer relationships, net	635,884	611,615
Other intangible assets, net	166,166	175,839
Deferred charges and other assets, net	387,563	327,868
Total other assets, net	2,200,955	2,061,875
Total assets	11,244,125	10,890,253
Accounts payable	560,804	496,259
Accrued liabilities	609,472	537,483
Term loan	0	149,341
Total current liabilities	1,170,276	1,183,083
Long-term debt, net	3,349,402	3,678,654
Deferred income taxes	1,660,914	1,650,575
Pension and other post-retirement benefits	512,034	485,896
Total liabilities	6,692,626	6,998,208
Total Westlake Chemical Corporation stockholders' equity	4,068,774	3,523,629
Noncontrolling interests	482,725	368,416
Total equity	4,551,499	3,892,045	3,824,137	3,561,931
Total liabilities and equity	11,244,125	10,890,253
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	(6,398,674)	(4,832,599)
Inventories	0	0
Prepaid expenses and other current assets	(35,906)	(36,504)
Restricted cash	0	0
Total current assets	(6,434,580)	(4,869,103)
Property, plant and equipment, net	0	0
Goodwill	0	0
Customer relationships, net	0	0
Other intangible assets, net	0	(25,581)
Deferred charges and other assets, net	(11,426,403)	(10,832,054)
Total other assets, net	(11,426,403)	(10,857,635)
Total assets	(17,860,983)	(15,726,738)
Accounts payable	(6,220,016)	(4,807,780)
Accrued liabilities	(214,564)	(61,323)
Term loan		0
Total current liabilities	(6,434,580)	(4,869,103)
Long-term debt, net	(4,464,598)	(3,997,070)
Deferred income taxes	(22,882)	(22,494)
Pension and other post-retirement benefits	0	0
Total liabilities	(10,922,060)	(8,888,667)
Total Westlake Chemical Corporation stockholders' equity	(6,938,923)	(6,838,071)
Noncontrolling interests	0	0
Total equity	(6,938,923)	(6,838,071)
Total liabilities and equity	(17,860,983)	(15,726,738)
Westlake Chemical Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	334,111	146,990	144,899	303,131
Accounts receivable, net	3,060,591	2,117,540
Inventories	0	0
Prepaid expenses and other current assets	16,616	30,748
Restricted cash	0	0
Total current assets	3,411,318	2,295,278
Property, plant and equipment, net	0	0
Goodwill	0	0
Customer relationships, net	0	0
Other intangible assets, net	0	0
Deferred charges and other assets, net	9,890,164	9,170,042
Total other assets, net	9,890,164	9,170,042
Total assets	13,301,482	11,465,320
Accounts payable	5,821,323	4,330,375
Accrued liabilities	155,106	26,367
Term loan		0
Total current liabilities	5,976,429	4,356,742
Long-term debt, net	3,256,280	3,584,949
Deferred income taxes	0	0
Pension and other post-retirement benefits	0	0
Total liabilities	9,232,709	7,941,691
Total Westlake Chemical Corporation stockholders' equity	4,068,773	3,523,629
Noncontrolling interests	0	0
Total equity	4,068,773	3,523,629
Total liabilities and equity	13,301,482	11,465,320
100% Owned Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	33,089	53,006	22,602	6,818
Accounts receivable, net	4,048,824	3,329,871
Inventories	631,322	597,819
Prepaid expenses and other current assets	31,785	41,755
Restricted cash	1,275	0
Total current assets	4,746,295	4,022,451
Property, plant and equipment, net	4,330,104	4,475,943
Goodwill	854,896	791,706
Customer relationships, net	493,960	468,645
Other intangible assets, net	92,155	130,243
Deferred charges and other assets, net	551,732	874,003
Total other assets, net	1,992,743	2,264,597
Total assets	11,069,142	10,762,991
Accounts payable	830,824	748,364
Accrued liabilities	436,816	389,216
Term loan		0
Total current liabilities	1,267,640	1,137,580
Long-term debt, net	4,334,142	4,090,775
Deferred income taxes	1,577,209	1,581,260
Pension and other post-retirement benefits	364,011	360,622
Total liabilities	7,543,002	7,170,237
Total Westlake Chemical Corporation stockholders' equity	3,526,140	3,592,754
Noncontrolling interests	0	0
Total equity	3,526,140	3,592,754
Total liabilities and equity	11,069,142	10,762,991
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	311,033	259,457	$ 213,018	$ 352,576
Accounts receivable, net	432,238	323,931
Inventories	203,513	203,281
Prepaid expenses and other current assets	22,365	12,494
Restricted cash	7,351	160,527
Total current assets	976,500	959,690
Property, plant and equipment, net	2,013,533	1,944,119
Goodwill	156,446	154,847
Customer relationships, net	141,924	142,970
Other intangible assets, net	74,011	71,177
Deferred charges and other assets, net	1,372,070	1,115,877
Total other assets, net	1,744,451	1,484,871
Total assets	4,734,484	4,388,680
Accounts payable	128,673	225,300
Accrued liabilities	232,114	183,223
Term loan		149,341
Total current liabilities	360,787	557,864
Long-term debt, net	223,578	0
Deferred income taxes	106,587	91,809
Pension and other post-retirement benefits	148,023	125,274
Total liabilities	838,975	774,947
Total Westlake Chemical Corporation stockholders' equity	3,412,784	3,245,317
Noncontrolling interests	482,725	368,416
Total equity	3,895,509	3,613,733
Total liabilities and equity	$ 4,734,484	$ 4,388,680