Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Cash Flows) (Details) - USD ($) $ in Thousands			3 Months Ended		9 Months Ended
	Sep. 29, 2017	Aug. 04, 2014	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Financial Statements, Captions [Line Items]
Net income			$ 219,150	$ 70,014	$ 523,278	$ 314,570
Depreciation and amortization			153,634	94,229	448,533	227,193
Deferred income taxes					23,294	105,910
Net changes in working capital and other					(32,441)	(103,513)
Net cash provided by (used for) operating activities					962,664	544,160
Acquisition of business, net of cash acquired					0	(2,437,829)
Additions to property, plant and equipment			(133,369)	(180,170)	(414,271)	(467,330)
Additions to cost method investment					(47,000)	(4,000)
Proceeds from disposition of assets					171	213
Proceeds from involuntary conversion of assets					1,672	0
Receivable under Investment Management Agreement					0
Proceeds from sales and maturities of securities					0	662,938
Purchase of securities					0	(138,422)
Settlements of derivative instruments					(7)	(4,655)
Net cash used for investing activities					(459,435)	(2,389,085)
Intercompany financing					0	0
Receivable under Investment Management Agreement Financing Activity					0
Debt issuance costs					(376)	(35,207)
Dividends paid					(76,491)	(71,933)
Distributions to noncontrolling interests					(20,767)	(12,300)
Proceeds from debt issuance					0	1,428,512
Net proceeds from issuance of Westlake Chemical Partners LP common units	$ 110,739	$ 286,100			110,739	0
Proceeds from issuance of notes payable					5,946	5,597
Proceeds from term loan and drawdown of revolver					225,000	600,000
Restricted cash associated with term loan					154,000	(154,000)
Repayment of term loan					(150,000)	0
Repayment of notes payable					(6,695)	(10,602)
Repayment of revolver					(550,000)	(125,000)
Repurchase of common stock for treasury					0	(67,406)
Other					2,204	2,840
Net cash provided by (used for) financing activities					(306,440)	1,560,501
Effect of exchange rate changes on cash and cash equivalents					21,991	2,418
Net increase (decrease) in cash and cash equivalents					218,780	(282,006)
Cash and cash equivalents at beginning of period					459,453	662,525
Cash and cash equivalents at end of period			678,233	380,519	678,233	380,519
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net income			(212,989)	(52,391)	(505,981)	(297,715)
Depreciation and amortization					0	0
Deferred income taxes					0	0
Net changes in working capital and other					505,981	297,715
Net cash provided by (used for) operating activities					0	0
Acquisition of business, net of cash acquired						0
Additions to property, plant and equipment					0	0
Additions to cost method investment					0	0
Proceeds from disposition of assets					0	0
Proceeds from involuntary conversion of assets					0
Receivable under Investment Management Agreement					119,000
Proceeds from sales and maturities of securities						0
Purchase of securities						0
Settlements of derivative instruments					0	0
Net cash used for investing activities					119,000	0
Intercompany financing					0	0
Receivable under Investment Management Agreement Financing Activity					(119,000)
Debt issuance costs					0	0
Dividends paid					0	0
Distributions to noncontrolling interests					0	0
Proceeds from debt issuance						0
Net proceeds from issuance of Westlake Chemical Partners LP common units					0
Proceeds from issuance of notes payable					0	0
Proceeds from term loan and drawdown of revolver					0	0
Restricted cash associated with term loan					0	0
Repayment of term loan					0
Repayment of notes payable					0	0
Repayment of revolver					0	0
Repurchase of common stock for treasury						0
Other					0	0
Net cash provided by (used for) financing activities					(119,000)	0
Effect of exchange rate changes on cash and cash equivalents					0	0
Net increase (decrease) in cash and cash equivalents					0	0
Cash and cash equivalents at beginning of period					0	0
Cash and cash equivalents at end of period			0	0	0	0
Westlake Chemical Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net income			210,831	65,662	501,849	299,914
Depreciation and amortization					0	0
Deferred income taxes					(217)	(5,178)
Net changes in working capital and other					(532,120)	(313,676)
Net cash provided by (used for) operating activities					(30,488)	(18,940)
Acquisition of business, net of cash acquired						0
Additions to property, plant and equipment					0	0
Additions to cost method investment					0	0
Proceeds from disposition of assets					0	0
Proceeds from involuntary conversion of assets					0
Receivable under Investment Management Agreement					0
Proceeds from sales and maturities of securities						658,338
Purchase of securities						(138,422)
Settlements of derivative instruments					0	0
Net cash used for investing activities					0	519,916
Intercompany financing					498,272	(2,242,604)
Receivable under Investment Management Agreement Financing Activity					119,000
Debt issuance costs					(376)	(33,617)
Dividends paid					(76,491)	(71,933)
Distributions to noncontrolling interests					0	0
Proceeds from debt issuance						1,428,512
Net proceeds from issuance of Westlake Chemical Partners LP common units					0
Proceeds from issuance of notes payable					0	0
Proceeds from term loan and drawdown of revolver					225,000	450,000
Restricted cash associated with term loan					0	0
Repayment of term loan					0
Repayment of notes payable					0	0
Repayment of revolver					(550,000)	(125,000)
Repurchase of common stock for treasury						(67,406)
Other					2,204	2,840
Net cash provided by (used for) financing activities					217,609	(659,208)
Effect of exchange rate changes on cash and cash equivalents					0	0
Net increase (decrease) in cash and cash equivalents					187,121	(158,232)
Cash and cash equivalents at beginning of period					146,990	303,131
Cash and cash equivalents at end of period			334,111	144,899	334,111	144,899
100% Owned Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income			98,276	(64,216)	170,868	(46,596)
Depreciation and amortization					294,227	118,645
Deferred income taxes					20,299	100,908
Net changes in working capital and other					(129,330)	(39,859)
Net cash provided by (used for) operating activities					356,064	133,098
Acquisition of business, net of cash acquired						(2,437,829)
Additions to property, plant and equipment					(294,138)	(162,288)
Additions to cost method investment					(47,000)	(4,000)
Proceeds from disposition of assets					25	48
Proceeds from involuntary conversion of assets					0
Receivable under Investment Management Agreement					0
Proceeds from sales and maturities of securities						0
Purchase of securities						0
Settlements of derivative instruments					(7)	(4,655)
Net cash used for investing activities					(341,120)	(2,608,724)
Intercompany financing					(313,276)	2,289,200
Receivable under Investment Management Agreement Financing Activity					0
Debt issuance costs					0	0
Dividends paid					0	0
Distributions to noncontrolling interests					279,203	202,210
Proceeds from debt issuance						0
Net proceeds from issuance of Westlake Chemical Partners LP common units					0
Proceeds from issuance of notes payable					0	0
Proceeds from term loan and drawdown of revolver					0	0
Restricted cash associated with term loan					0	0
Repayment of term loan					0
Repayment of notes payable					(788)	0
Repayment of revolver					0	0
Repurchase of common stock for treasury						0
Other					0	0
Net cash provided by (used for) financing activities					(34,861)	2,491,410
Effect of exchange rate changes on cash and cash equivalents					0	0
Net increase (decrease) in cash and cash equivalents					(19,917)	15,784
Cash and cash equivalents at beginning of period					53,006	6,818
Cash and cash equivalents at end of period			33,089	22,602	33,089	22,602
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income			123,032	120,959	356,542	358,967
Depreciation and amortization					154,306	108,548
Deferred income taxes					3,212	10,180
Net changes in working capital and other					123,028	(47,693)
Net cash provided by (used for) operating activities					637,088	430,002
Acquisition of business, net of cash acquired						0
Additions to property, plant and equipment					(120,133)	(305,042)
Additions to cost method investment					0	0
Proceeds from disposition of assets					146	165
Proceeds from involuntary conversion of assets					1,672
Receivable under Investment Management Agreement					(119,000)
Proceeds from sales and maturities of securities						4,600
Purchase of securities						0
Settlements of derivative instruments					0	0
Net cash used for investing activities					(237,315)	(300,277)
Intercompany financing					(184,996)	(46,596)
Receivable under Investment Management Agreement Financing Activity					0
Debt issuance costs					0	(1,590)
Dividends paid					0	0
Distributions to noncontrolling interests					(299,970)	(214,510)
Proceeds from debt issuance						0
Net proceeds from issuance of Westlake Chemical Partners LP common units					110,739
Proceeds from issuance of notes payable					5,946	5,597
Proceeds from term loan and drawdown of revolver					0	150,000
Restricted cash associated with term loan					154,000	(154,000)
Repayment of term loan					(150,000)
Repayment of notes payable					(5,907)	(10,602)
Repayment of revolver					0	0
Repurchase of common stock for treasury						0
Other					0	0
Net cash provided by (used for) financing activities					(370,188)	(271,701)
Effect of exchange rate changes on cash and cash equivalents					21,991	2,418
Net increase (decrease) in cash and cash equivalents					51,576	(139,558)
Cash and cash equivalents at beginning of period					259,457	352,576
Cash and cash equivalents at end of period			$ 311,033	$ 213,018	$ 311,033	$ 213,018