Accumulated Other Comprehensive Income Reclassifications in AOCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income taxes	$ 294,605		$ 263,018		$ 797,862		$ 684,100
Realized gain on available-for-sale investments	(2,670)		(287)		4,440		3,137
Provision for income taxes	(124,449)		(92,728)		(300,231)		(244,647)
Net income to Westlake Chemical Corporation	167,757		170,290		495,232		439,453
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income to Westlake Chemical Corporation	(148)		(428)		355		(1,233)
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service costs	(87)	[1]	(95)	[1]	(261)	[1]	(286)	[2]
Net loss	(153)	[1]	(600)	[1]	(424)	[1]	(1,718)	[2]
Income before income taxes	(240)		(695)		(685)		(2,004)
Provision for income taxes	92		267		263		771
Net income to Westlake Chemical Corporation	(148)		(428)		(422)		(1,233)
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized gain on available-for-sale investments	0		0		1,212		0
Provision for income taxes	0		0		(435)		0
Net income to Westlake Chemical Corporation	$ 0		$ 0		$ 777		$ 0

[1] These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. For additional information, please read Note 10 (Employee Benefits) to the financial statements included in the 2013 Form 10-K.

[2] Share amounts and per share data for the three and nine months ended September 30, 2013 have been restated to reflect the effect of a two-for-one stock split on March 18, 2014. See Note 1 for additional information.