Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (89)	$ (36)
Ending balance	(67)	(45)
Pension and Other Post-Retirement Benefits Liability, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	52	20
Net other comprehensive income (loss) attributable to Westlake Corporation		0
Ending balance	52	20
Cumulative Foreign Currency Exchange, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(141)	(56)
Net other comprehensive income (loss) attributable to Westlake Corporation	23	(9)
Ending balance	(118)	(65)
Other, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0	0
Net other comprehensive income (loss) attributable to Westlake Corporation	(1)	0
Ending balance	(1)	0
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net other comprehensive income (loss) attributable to Westlake Corporation	$ 22	$ (9)