Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 7,955
Accumulated other comprehensive loss	(45)		$ (36)
Ending balance	8,681
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	0	0
Ending balance	20	(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	(9)	(6)
Ending balance	(65)	(46)
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(36)	(64)
Net other comprehensive income (loss) attributable to Westlake Chemical Corporation	$ (9)	$ (6)