Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 7,955
Ending balance	9,621
Pension and Other Post-Retirement Benefits Liability, Net of Tax
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	20	$ (24)
Other comprehensive gain (loss) attributable to Westlake Corporation	1	0
Ending balance	21	(24)
Cumulative Foreign Currency Exchange, Net of Tax
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(56)	(40)
Other comprehensive gain (loss) attributable to Westlake Corporation	(196)	(11)
Ending balance	(252)	(51)
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(36)	(64)
Other comprehensive gain (loss) attributable to Westlake Corporation	(195)	(11)
Ending balance	$ (231)	$ (75)