Earnings and Dividends per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings and Dividends Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$ 522	$ 15	$ 764	$ 160
Net income attributable to participating securities	(2)	(1)	(4)	(1)
Net income attributable to common shareholders	$ 520	$ 14	$ 760	$ 159