Guarantor Disclosures (Condensed Consolidating Financial Information Statement Of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 1,034,867	$ 867,252
Cost of sales	862,230	699,668
Gross profit	172,637	167,584
Selling, general and administrative expenses	27,012	26,947
Income from operations	145,625	140,637
Interest expense	(12,177)	(12,920)
Other income (expense), net	1,347	1,207
Income before income taxes	134,795	128,924
(Benefit from) provision for income taxes	46,982	45,380
Equity in net income of subsidiaries
Net income	87,813	83,544
Comprehensive income (loss)	105,019	84,352
Westlake Chemical Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales
Cost of sales
Gross profit
Selling, general and administrative expenses	505	1,012
Income from operations	(505)	(1,012)
Interest expense	(12,171)	(12,909)
Other income (expense), net	3,534	3,196
Income before income taxes	(9,142)	(10,725)
(Benefit from) provision for income taxes	(3,173)	(3,518)
Equity in net income of subsidiaries	93,782	90,751
Net income	87,813	83,544
Comprehensive income (loss)	105,019	84,352
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	1,026,332	859,951
Cost of sales	854,987	692,240
Gross profit	171,345	167,711
Selling, general and administrative expenses	24,756	24,749
Income from operations	146,589	142,962
Interest expense	(6)	(11)
Other income (expense), net	(1,700)	(2,715)
Income before income taxes	144,883	140,236
(Benefit from) provision for income taxes	50,231	49,146
Equity in net income of subsidiaries
Net income	94,652	91,090
Comprehensive income (loss)	111,344	91,365
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	9,843	8,146
Cost of sales	8,551	8,273
Gross profit	1,292	(127)
Selling, general and administrative expenses	1,751	1,186
Income from operations	(459)	(1,313)
Other income (expense), net	(487)	726
Income before income taxes	(946)	(587)
(Benefit from) provision for income taxes	(76)	(248)
Equity in net income of subsidiaries
Net income	(870)	(339)
Comprehensive income (loss)	(358)	194
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	(1,308)	(845)
Cost of sales	(1,308)	(845)
Gross profit
Selling, general and administrative expenses
Income from operations
Interest expense
Other income (expense), net
Income before income taxes
(Benefit from) provision for income taxes
Equity in net income of subsidiaries	(93,782)	(90,751)
Net income	(93,782)	(90,751)
Comprehensive income (loss)	$ (110,986)	$ (91,559)