Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 7,955
Accumulated other comprehensive loss	(116)		$ (36)
Ending balance	9,404
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	20	$ (24)
Net other comprehensive income (loss) attributable to Westlake Chemical Corporation	1	0
Ending balance	21	(24)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(56)	(40)
Net other comprehensive income (loss) attributable to Westlake Chemical Corporation	(81)	8
Ending balance	(137)	(32)
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(36)	(64)
Net other comprehensive income (loss) attributable to Westlake Chemical Corporation	(80)	8
Ending balance	$ (116)	$ (56)