Consolidated Statements Of Changes In Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Common Stock, Held In Treasury, At Cost [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Benefits Liability Net Of Tax [Member]	Cumulative Foreign Currency Exchange [Member]	Net Unrealized Holding Gains On Investments, Net Of Tax [Member]	Noncontrolling Interest [Member]
Total equity, beginning balance at Dec. 31, 2011	$ 1,756,312	$ 1,332	$ (2,518)	$ 467,130	$ 1,299,438	$ (15,143)	$ 4,888	$ 1,185	$ 0
Number of shares, beginning balance at Dec. 31, 2011		133,203,818	139,632
Net income	385,555				385,555				0
Other comprehensive (loss) income	(1,770)					(1,208)	623	(1,185)	0
Common stock repurchased, shares			429,354
Common stock repurchased	(10,784)		(10,784)						0
Shares issued - stock based compensation, shares		1,170,630
Shares issued - stock based compensation	10,370	12		10,358
Stock-based compensation, net of tax on stock options exercised	18,094			18,094
Dividends paid	(285,521)				(285,521)
Total equity, ending balance at Dec. 31, 2012	1,872,256	1,344	(13,302)	495,582	1,399,472	(16,351)	5,511	0	0
Number of shares, ending balance at Dec. 31, 2012		134,374,448	568,986
Net income	610,425				610,425				0
Other comprehensive (loss) income	8,224					9,655	(1,607)	176	0
Common stock repurchased, shares			683,936
Common stock repurchased	(32,918)		(32,918)						0
Shares issued - stock based compensation, shares		205,760
Shares issued - stock based compensation	3,437	2		3,435
Stock-based compensation, net of tax on stock options exercised	12,415			12,415
Dividends paid	(55,236)				(55,236)
Total equity, ending balance at Dec. 31, 2013	2,418,603	1,346	(46,220)	511,432	1,954,661	(6,696)	3,904	176	0
Number of shares, ending balance at Dec. 31, 2013		134,580,208	1,252,922
Net income	685,016				678,523				6,493
Other comprehensive (loss) income	(76,817)					(16,746)	(60,128)	57	0
Common stock repurchased, shares			671,791
Common stock repurchased	(52,630)		(52,630)						0
Shares issued - stock based compensation, shares		98,856	(137,167)
Shares issued - stock based compensation	5,524	1	2,478	3,045
Stock-based compensation, net of tax on stock options exercised	15,964			15,964
Dividends paid	(77,656)				(77,656)
Distributions to noncontrolling interests	(2,204)								(2,204)
Issuance of Westlake Chemical Partners LP common units	286,088								286,088
Total equity, ending balance at Dec. 31, 2014	$ 3,201,888	$ 1,347	$ (96,372)	$ 530,441	$ 2,555,528	$ (23,442)	$ (56,224)	$ 233	$ 290,377
Number of shares, ending balance at Dec. 31, 2014		134,679,064	1,787,546