Earnings and Dividends per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings and Dividends Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$ 607	$ 57	$ 1,371	$ 217
Net income attributable to participating securities	(3)	0	(7)	(1)
Net income attributable to common shareholders	$ 604	$ 57	$ 1,364	$ 216