Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 1,034	$ 1,339	$ 420
Pension and other post-retirement benefits
Pension and other post-retirement benefits reserves adjustment	(33)	19	60
Amortization of benefits liability	0	2	1
Income tax benefit (provision) on pension and other post-retirement benefits	8	(7)	(24)
Foreign Currency Translation Adjustment
Foreign currency translation	(59)	124	(34)
Income tax provision on foreign currency translation	0	(5)	0
Available-for-sale investments
Unrealized holding gains on investments	0	0	62
Reclassification of net realized gains to net income	0	0	(54)
Income tax provision on available-for-sale investments	0	0	(3)
Other comprehensive income (loss), net of income taxes	(84)	133	8
Comprehensive income	950	1,472	428
Comprehensive income attributable to noncontrolling interests, net of tax of $4, $1 and $0 for 2018, 2017 and 2016, respectively	36	40	21
Comprehensive income attributable to Westlake Chemical Corporation	$ 914	$ 1,432	$ 407