Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Condensed Financial Statements, Captions [Line Items]
Net income	$ 70,014	$ 188,420	$ 314,570	$ 548,888
Depreciation and amortization			228,211	181,733
Deferred income taxes			105,910	7,585
Net changes in working capital and other			(104,531)	103,094
Net cash provided by operating activities			544,160	841,300
Acquisition of business, net of cash acquired			(2,437,829)	15,782
Additions to cost method investment			(4,000)	0
Additions to property, plant and equipment	(180,170)	(125,304)	(467,330)	(329,236)
Proceeds from disposition of assets			213	17
Proceeds from disposition of equity method investment			0	27,865
Proceeds from sales and maturities of securities			662,938	16,056
Purchase of securities			(138,422)	(282,542)
Settlements of derivative instruments			(4,655)	(1,535)
Net cash used for investing activities			(2,389,085)	(553,593)
Intercompany financing			0	0
Debt issuance costs			(35,207)	0
Dividends paid			(71,933)	(67,852)
Distributions to noncontrolling interests			(12,300)	(10,982)
Proceeds from debt issuance			(1,428,512)	0
Proceeds from exercise of stock options			1,650	984
Proceeds from issuance of notes payable			5,597	19,483
Proceeds from term loan and drawdown of revolver			600,000	0
Restricted cash associated with term loan			(154,000)	0
Repayment of notes payable			(10,602)	(32,954)
Repayment of revolver			(125,000)	0
Repurchase of common stock for treasury			(67,406)	(114,254)
Windfall tax benefits from share-based payment arrangements			1,190	2,452
Net cash provided by (used for) financing activities			1,560,501	(203,123)
Effect of exchange rate changes on cash and cash equivalents			2,418	(3,260)
Net (decrease) increase in cash and cash equivalents			(282,006)	81,324
Cash and cash equivalents at beginning of period			662,525	880,601
Cash and cash equivalents at end of period	380,519	961,925	380,519	961,925
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	(52,391)	(190,325)	(297,715)	(545,531)
Depreciation and amortization			0	0
Deferred income taxes			0	0
Net changes in working capital and other			297,715	545,531
Net cash provided by operating activities			0	0
Acquisition of business, net of cash acquired			0	0
Additions to cost method investment			0
Additions to property, plant and equipment			0	0
Proceeds from disposition of assets			0	0
Proceeds from disposition of equity method investment				0
Proceeds from sales and maturities of securities			0	0
Purchase of securities			0	0
Settlements of derivative instruments			0	0
Net cash used for investing activities			0	0
Intercompany financing			0	0
Debt issuance costs			0
Dividends paid			0	0
Distributions to noncontrolling interests			0	0
Proceeds from exercise of stock options			0	0
Proceeds from issuance of notes payable			0	0
Proceeds from term loan and drawdown of revolver			0
Restricted cash associated with term loan			0
Repayment of notes payable			0	0
Repayment of revolver			0
Repurchase of common stock for treasury			0	0
Windfall tax benefits from share-based payment arrangements			0	0
Net cash provided by (used for) financing activities			0	0
Effect of exchange rate changes on cash and cash equivalents			0	0
Net (decrease) increase 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	65,662	183,604	299,914	535,041
Depreciation and amortization			747	1,504
Deferred income taxes			(5,178)	87
Net changes in working capital and other			(314,423)	(567,137)
Net cash provided by operating activities			(18,940)	(30,505)
Acquisition of business, net of cash acquired			0	0
Additions to cost method investment			0
Additions to property, plant and equipment			0	0
Proceeds from disposition of assets			0	0
Proceeds from disposition of equity method investment				0
Proceeds from sales and maturities of securities			658,338	16,056
Purchase of securities			(138,422)	(282,542)
Settlements of derivative instruments			0	0
Net cash used for investing activities			519,916	(266,486)
Intercompany financing			(2,242,604)	467,360
Debt issuance costs			(33,617)
Dividends paid			(71,933)	(67,852)
Distributions to noncontrolling interests			0	0
Proceeds from debt issuance			(1,428,512)
Proceeds from exercise of stock options			1,650	984
Proceeds from issuance of notes payable			0	0
Proceeds from term loan and drawdown of revolver			450,000
Restricted cash associated with term loan			0
Repayment of notes payable			0	0
Repayment of revolver			(125,000)
Repurchase of common stock for treasury			(67,406)	(114,254)
Windfall tax benefits from share-based payment arrangements			1,190	2,452
Net cash provided by (used for) financing activities			(659,208)	288,690
Effect of exchange rate changes on cash and cash equivalents			0	0
Net (decrease) increase in cash and cash equivalents			(158,232)	(8,301)
Cash and cash equivalents at beginning of period			303,131	655,947
Cash and cash equivalents at end of period	144,899	647,646	144,899	647,646
100% Owned Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	(6,026)	92,530	23,947	237,804
Depreciation and amortization			98,658	81,770
Deferred income taxes			111,795	3,972
Net changes in working capital and other			93,280	110,574
Net cash provided by operating activities			327,680	434,120
Acquisition of business, net of cash acquired			0	0
Additions to cost method investment			0
Additions to property, plant and equipment			(163,579)	(137,844)
Proceeds from disposition of assets			48	0
Proceeds from disposition of equity method investment				27,865
Proceeds from sales and maturities of securities			0	0
Purchase of securities			0	0
Settlements of derivative instruments			(4,655)	(1,535)
Net cash used for investing activities			(168,186)	(111,514)
Intercompany financing			(366,639)	(570,217)
Debt issuance costs			0
Dividends paid			0	0
Distributions to noncontrolling interests			202,211	249,999
Proceeds from exercise of stock options			0	0
Proceeds from issuance of notes payable			0	0
Proceeds from term loan and drawdown of revolver			0
Restricted cash associated with term loan			0
Repayment of notes payable			0	0
Repayment of revolver			0
Repurchase of common stock for treasury			0	0
Windfall tax benefits from share-based payment arrangements			0	0
Net cash provided by (used for) financing activities			(164,428)	(320,218)
Effect of exchange rate changes on cash and cash equivalents			0	0
Net (decrease) increase in cash and cash equivalents			(4,934)	2,388
Cash and cash equivalents at beginning of period			6,818	3,047
Cash and cash equivalents at end of period	1,884	5,435	1,884	5,435
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	62,769	102,611	288,424	321,574
Depreciation and amortization			128,806	98,459
Deferred income taxes			(707)	3,526
Net changes in working capital and other			(181,103)	14,126
Net cash provided by operating activities			235,420	437,685
Acquisition of business, net of cash acquired			(2,437,829)	15,782
Additions to cost method investment			(4,000)
Additions to property, plant and equipment			(303,751)	(191,392)
Proceeds from disposition of assets			165	17
Proceeds from disposition of equity method investment				0
Proceeds from sales and maturities of securities			4,600	0
Purchase of securities			0	0
Settlements of derivative instruments			0	0
Net cash used for investing activities			(2,740,815)	(175,593)
Intercompany financing			2,609,243	102,857
Debt issuance costs			(1,590)
Dividends paid			0	0
Distributions to noncontrolling interests			(214,511)	(260,981)
Proceeds from exercise of stock options			0	0
Proceeds from issuance of notes payable			5,597	19,483
Proceeds from term loan and drawdown of revolver			150,000
Restricted cash associated with term loan			(154,000)
Repayment of notes payable			(10,602)	(32,954)
Repayment of revolver			0
Repurchase of common stock for treasury			0	0
Windfall tax benefits from share-based payment arrangements			0	0
Net cash provided by (used for) financing activities			2,384,137	(171,595)
Effect of exchange rate changes on cash and cash equivalents			2,418	(3,260)
Net (decrease) increase in cash and cash equivalents			(118,840)	87,237
Cash and cash equivalents at beginning of period			352,576	221,607
Cash and cash equivalents at end of period	$ 233,736	$ 308,844	$ 233,736	$ 308,844