Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 6,043
Net other comprehensive income (loss) attributable to Westlake Corporation	28	$ 10
Ending balance	7,955	6,043
Pension and Other Post-Retirement Benefits Liability, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(24)	3
Net other comprehensive income (loss) attributable to Westlake Corporation	44	(27)
Ending balance	20	(24)
Cumulative Foreign Currency Exchange, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(40)	(77)
Net other comprehensive income (loss) attributable to Westlake Corporation	(16)	37
Ending balance	$ (56)	(40)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ (74)