Earnings and Dividends per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings and Dividends Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$ 145	$ 72
Net income attributable to participating securities	0	(1)
Net income attributable to common shareholders	$ 145	$ 71