Accumulated Other Comprehensive Income Reclassifications in AOCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income (Loss) from Continuing Operations before Income Taxes									$ 1,083,918	$ 942,172	$ 585,169
Provision for income taxes									(398,902)	(331,747)	(199,614)
Other (expense) income, net									(2,721)	6,790	3,520
Net income attributable to Westlake Chemical Corporation	183,291	167,757	169,443	158,032	170,972	170,290	145,816	123,347	678,523	610,425	385,555
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income attributable to Westlake Chemical Corporation									209	(1,681)
Amortization of pension and other post-retirement items | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service costs									(347)	(381)
Net loss									(577)	(2,331)
Income (Loss) from Continuing Operations before Income Taxes									(924)	(2,712)
Provision for income taxes									356	1,043
Net income attributable to Westlake Chemical Corporation									(568)	(1,669)
Net unrealized gains on available-for-sale investments | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Provision for income taxes									(435)	7
Other (expense) income, net									1,212	(19)
Net income attributable to Westlake Chemical Corporation									$ 777	$ (12)