Earnings per Share (Schedule Of Net Income Attributable To Common Stockholders) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$ 802	$ 211	$ 153	$ 138	$ 99	$ 66	$ 111	$ 123	$ 1,304	$ 399	$ 646
Participating Securities, Distributed and Undistributed Earnings (Loss), Diluted									(7)	(2)	(3)
Net income attributable to common shareholders									$ 1,297	$ 397	$ 643