Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 69	$ 166	$ 250	$ 377
Foreign Currency Translation Adjustment, by Component [Abstract]
Foreign currency translation	10	(9)	0	4
Income tax benefit (provision) on foreign currency translation	9	(7)	7	(9)
Other comprehensive income (loss), net of income taxes	19	(16)	7	(5)
Comprehensive income	88	150	257	372
Comprehensive income attributable to noncontrolling interests, net of tax of $0 and $1 for the three months ended September 30, 2020 and 2019; and net of tax of $1 and $2 for the nine months ended September 30, 2020 and 2019, respectively	13	8	35	27
Comprehensive income attributable to Westlake Chemical Corporation	$ 75	$ 142	$ 222	$ 345