Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 373	$ 462	$ 1,034
Pension and other post-retirement benefits
Pension and other post-retirement benefits reserves adjustment	(37)	(32)	(33)
Income tax benefit on pension and other post-retirement benefits	10	8	8
Foreign currency translation adjustments
Foreign currency translation	23	17	(59)
Income tax benefit (provision) on foreign currency translation	18	(4)	0
Other comprehensive income (loss), net of income taxes	14	(11)	(84)
Comprehensive income	387	451	950
Comprehensive income attributable to noncontrolling interests, net of tax of $1, $2 and $4 for 2020, 2019 and 2018, respectively	47	42	36
Comprehensive income attributable to Westlake Chemical Corporation	$ 340	$ 409	$ 914