Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 219,150	$ 70,014	$ 523,278	$ 314,570
Pension and other post-retirement benefits liability
Pension and other post-retirement reserves adjustment (excluding amortization)	0	(206)	0	(412)
Amortization of benefits liability	529	369	1,600	1,072
Income tax provision on pension and other post- retirement benefits liability	(193)	(60)	(543)	(251)
Foreign Currency Translation Adjustment, by Component [Abstract]
Foreign currency translation	39,714	6,453	108,166	15,758
Income tax provision on foreign currency translation	(76)	0	(1,603)	0
Net unrealized holding gains (losses) on investments
Unrealized holding gains on investments	0	1,550	0	61,524
Reclassification of net realized gains to net income	0	(52,401)	0	(53,720)
Income tax provision on available-for-sale investments	0	18,270	0	(2,805)
Other	(96)	0	(260)	0
Other comprehensive income (loss), net of income taxes	39,878	(26,025)	107,360	21,166
Comprehensive income	259,028	43,989	630,638	335,736
Comprehensive income attributable to noncontrolling interests, net of tax of $846 and $0 for the three months ended September 30, 2017 and 2016, respectively; and $2,467 and $0 for the nine months ended September 30, 2017 and 2016, respectively.	4,628	4,352	17,288	14,656
Comprehensive income attributable to Westlake Chemical Corporation	$ 254,400	$ 39,637	$ 613,350	$ 321,080