Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 536	$ 24	$ 789	$ 181
Foreign Currency Translation Adjustment, by Component [Abstract]
Foreign currency translation	12	15	15	(10)
Income tax benefit (provision) on foreign currency translation	3	5	(7)	(2)
Other comprehensive income (loss), net of income taxes	15	20	8	(12)
Comprehensive income	551	44	797	169
Comprehensive income attributable to noncontrolling interests, net of tax of $1 and $0 for the three months ended June 30, 2021 and 2020; and net of tax of $1 and $1 for the six months ended June 30, 2021 and 2020, respectively	15	10	25	22
Comprehensive income attributable to Westlake Chemical Corporation	$ 536	$ 34	$ 772	$ 147