Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 620	$ 69	$ 1,409	$ 250
Pension and other post-retirement benefits liability
Pension and other post-retirement benefits reserves adjustment	1	0	1	0
Income tax provision on pension and other post-retirement benefits liability	(1)	0	(1)	0
Foreign currency translation adjustments
Foreign currency translation	(13)	10	2	0
Income tax benefit (provision) on foreign currency translation	(6)	9	(13)	7
Other comprehensive income (loss), net of income taxes	(19)	19	(11)	7
Comprehensive income	601	88	1,398	257
Comprehensive income attributable to noncontrolling interests, net of tax of $1 and $0 for the three months ended September 30, 2021 and 2020; and net of tax of $2 and $1 for the nine months ended September 30, 2021 and 2020, respectively	13	13	38	35
Comprehensive income attributable to Westlake Chemical Corporation	$ 588	$ 75	$ 1,360	$ 222