Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (98)	$ (89)
Ending balance	(132)	(67)
Pension and Other Post-Retirement Benefits Liability, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	4	52
Net other comprehensive income (loss) attributable to Westlake Corporation	1	0
Ending balance	5	52
Cumulative Foreign Currency Exchange, Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(102)	(141)
Net other comprehensive income (loss) attributable to Westlake Corporation	(35)	23
Ending balance	(137)	(118)
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	0	(1)
Ending balance	0	(1)
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net other comprehensive income (loss) attributable to Westlake Corporation	$ (34)	$ 22