Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Condensed Financial Statements, Captions [Line Items]
Net income	$ 115,620	$ 210,061	$ 244,556	$ 360,468
Depreciation and amortization			133,381	119,983
Deferred income taxes			102,990	3,088
Net changes in working capital and other			(111,035)	(48,184)
Net cash provided by operating activities			369,892	435,355
Acquisition of business, net of cash acquired			0	15,782
Additions to property, plant and equipment	(150,833)	(108,110)	(287,160)	(203,933)
Proceeds from disposition of assets			105	0
Proceeds from sales and maturities of securities			302,432	15,037
Purchase of securities			(138,422)
Settlements of derivative instruments			(3,372)	(1,174)
Net cash provided by (used for) investing activities			(126,417)	(174,288)
Intercompany financing			0	0
Intercompany financing—OpCo			0	0
Debt issuance costs			(9,700)	0
Dividends paid			(47,317)	(43,896)
Distributions paid			(8,084)	(7,218)
Purchase of limited partner interests				0
Proceeds from exercise of stock options			481	831
Proceeds from issuance of notes payable			3,842	2,392
Repayment of notes payable			(8,626)	(4,299)
Repurchase of common stock for treasury			(67,404)	(62,804)
Windfall tax benefits from share-based payment arrangements			319	1,895
Net cash provided by financing activities			(136,489)	(113,099)
Effect of exchange rate changes on cash and cash equivalents			1,486	(2,000)
Net increase in cash and cash equivalents			108,472	145,968
Cash and cash equivalents at beginning of period			662,525	880,601
Cash and cash equivalents at end of period	770,997	1,026,569	770,997	1,026,569
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Net income	111,124	205,095	234,252	351,437
Depreciation and amortization			417	1,002
Deferred income taxes			(4,802)	(40)
Net changes in working capital and other			(275,002)	(371,716)
Net cash provided by operating activities			(45,135)	(19,317)
Acquisition of business, net of cash acquired				0
Additions to property, plant and equipment			0	0
Proceeds from disposition of assets			0
Proceeds from sales and maturities of securities			302,432	15,037
Purchase of securities			(130,830)
Settlements of derivative instruments			0	0
Net cash provided by (used for) investing activities			171,602	15,037
Intercompany financing			106,904	208,692
Intercompany financing—OpCo			0	0
Debt issuance costs			(9,700)
Dividends paid			(47,317)	(43,896)
Distributions paid			0	0
Purchase of limited partner interests				0
Proceeds from exercise of stock options			481	831
Proceeds from issuance of notes payable			0	0
Repayment of notes payable			0	0
Repurchase of common stock for treasury			(67,404)	(62,804)
Windfall tax benefits from share-based payment arrangements			319	1,895
Net cash provided by financing activities			(16,717)	104,718
Effect of exchange rate changes on cash and cash equivalents			0	0
Net increase in cash and cash equivalents			109,750	100,438
Cash and cash equivalents at beginning of period			303,131	655,947
Cash and cash equivalents at end of period	412,881	756,385	412,881	756,385
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income	90,323	167,066	198,563	304,242
Depreciation and amortization			71,640	59,792
Deferred income taxes			105,828	929
Net changes in working capital and other			(194,894)	(310,600)
Net cash provided by operating activities			181,137	54,363
Acquisition of business, net of cash acquired				0
Additions to property, plant and equipment			(101,270)	(95,363)
Proceeds from disposition of assets			7
Proceeds from sales and maturities of securities			0	0
Purchase of securities			(7,592)
Settlements of derivative instruments			(3,372)	(1,174)
Net cash provided by (used for) investing activities			(112,227)	(96,537)
Intercompany financing			(233,536)	(269,281)
Intercompany financing—OpCo			500	135,341
Debt issuance costs			0
Dividends paid			0	0
Distributions paid			158,393	176,980
Purchase of limited partner interests				0
Proceeds from exercise of stock options			0	0
Proceeds from issuance of notes payable			0	0
Repayment of notes payable			0	0
Repurchase of common stock for treasury			0	0
Windfall tax benefits from share-based payment arrangements			0	0
Net cash provided by financing activities			(74,643)	43,040
Effect of exchange rate changes on cash and cash equivalents			0	0
Net increase in cash and cash equivalents			(5,733)	866
Cash and cash equivalents at beginning of period			6,828	3,057
Cash and cash equivalents at end of period	1,095	3,923	1,095	3,923
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Net income	82,848	88,556	187,418	177,899
Depreciation and amortization			41,182	40,195
Deferred income taxes			320	(234)
Net changes in working capital and other			(40,445)	15,748
Net cash provided by operating activities			188,475	233,608
Acquisition of business, net of cash acquired				0
Additions to property, plant and equipment			(168,533)	(95,514)
Proceeds from disposition of assets			98
Proceeds from sales and maturities of securities			0	0
Purchase of securities			0
Settlements of derivative instruments			0	0
Net cash provided by (used for) investing activities			(168,435)	(95,514)
Intercompany financing			131,832	53,354
Intercompany financing—OpCo			(500)	(135,341)
Debt issuance costs			0
Dividends paid			0	0
Distributions paid			(172,463)	(189,103)
Purchase of limited partner interests				135,341
Proceeds from exercise of stock options			0	0
Proceeds from issuance of notes payable			0	0
Repayment of notes payable			0	0
Repurchase of common stock for treasury			0	0
Windfall tax benefits from share-based payment arrangements			0	0
Net cash provided by financing activities			(41,131)	(135,749)
Effect of exchange rate changes on cash and cash equivalents			0	0
Net increase in cash and cash equivalents			(21,091)	2,345
Cash and cash equivalents at beginning of period			163,430	131,545
Cash and cash equivalents at end of period	142,339	133,890	142,339	133,890
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income	30,388	43,788	57,065	59,996
Depreciation and amortization			20,142	18,994
Deferred income taxes			1,644	2,433
Net changes in working capital and other			(33,436)	85,278
Net cash provided by operating activities			45,415	166,701
Acquisition of business, net of cash acquired				15,782
Additions to property, plant and equipment			(17,357)	(13,056)
Proceeds from disposition of assets			0
Proceeds from sales and maturities of securities			0	0
Purchase of securities			0
Settlements of derivative instruments			0	0
Net cash provided by (used for) investing activities			(17,357)	2,726
Intercompany financing			(5,200)	7,235
Intercompany financing—OpCo			0	0
Debt issuance costs			0
Dividends paid			0	0
Distributions paid			5,986	4,905
Purchase of limited partner interests				(135,341)
Proceeds from exercise of stock options			0	0
Proceeds from issuance of notes payable			3,842	2,392
Repayment of notes payable			(8,626)	(4,299)
Repurchase of common stock for treasury			0	0
Windfall tax benefits from share-based payment arrangements			0	0
Net cash provided by financing activities			(3,998)	(125,108)
Effect of exchange rate changes on cash and cash equivalents			1,486	(2,000)
Net increase in cash and cash equivalents			25,546	42,319
Cash and cash equivalents at beginning of period			189,136	90,052
Cash and cash equivalents at end of period	214,682	132,371	214,682	132,371
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	(199,063)	(294,444)	(432,742)	(533,106)
Depreciation and amortization			0	0
Deferred income taxes			0	0
Net changes in working capital and other			432,742	533,106
Net cash provided by operating activities			0	0
Acquisition of business, net of cash acquired				0
Additions to property, plant and equipment			0	0
Proceeds from disposition of assets			0
Proceeds from sales and maturities of securities			0	0
Purchase of securities			0
Settlements of derivative instruments			0	0
Net cash provided by (used for) investing activities			0	0
Intercompany financing			0	0
Intercompany financing—OpCo			0	0
Debt issuance costs			0
Dividends paid			0	0
Distributions paid			0	0
Purchase of limited partner interests				0
Proceeds from exercise of stock options			0	0
Proceeds from issuance of notes payable			0	0
Repayment of notes payable			0	0
Repurchase of common stock for treasury			0	0
Windfall tax benefits from share-based payment arrangements			0	0
Net cash provided by financing activities			0	0
Effect of exchange rate changes on cash and cash equivalents			0	0
Net 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