Consolidated Statements Of Changes In Stockholders' Equity Statement - USD ($) $ in Millions	Total	Common Stock [Member]	Common Stock, Held in Treasury [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]
Beginning balances at Dec. 31, 2018	$ 6,076	$ 1	$ (382)	$ 556	$ 5,477	$ (62)	$ 486
Beginning balance, shares issued at Dec. 31, 2018		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2018			6,183,125
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation					72
Net income attributable to noncontrolling interests							10
Net income	82
Other comprehensive income	(2)					(2)	0
Shares issued—stock- based compensation (in shares)			(124,052)
Shares issued—stock-based compensation	0		$ 11	(8)	(3)
Stock-based compensation	7			7
Dividends declared	(33)				(33)
Distributions to noncontrolling interests	(8)						(8)
Issuance of Westlake Chemical Partners LP common units	63			(2)			65
Ending balances at Mar. 31, 2019	6,185	$ 1	$ (371)	553	5,513	(64)	553
Ending balance, shares issued at Mar. 31, 2019		134,651,380
Ending balance, Treasury shares at Mar. 31, 2019			6,059,073
Beginning balances at Dec. 31, 2018	6,076	$ 1	$ (382)	556	5,477	(62)	486
Beginning balance, shares issued at Dec. 31, 2018		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2018			6,183,125
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation	191
Net income attributable to noncontrolling interests	20
Net income	211
Other comprehensive income	11
Ending balances at Jun. 30, 2019	6,259	$ 1	$ (390)	558	5,600	(50)	540
Ending balance, shares issued at Jun. 30, 2019		134,651,380
Ending balance, Treasury shares at Jun. 30, 2019			6,382,640
Beginning balances at Mar. 31, 2019	6,185	$ 1	$ (371)	553	5,513	(64)	553
Beginning balance, shares issued at Mar. 31, 2019		134,651,380
Beginning balance, Treasury shares at Mar. 31, 2019			6,059,073
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation	119				119
Net income attributable to noncontrolling interests	10						10
Net income	129
Other comprehensive income	13					14	(1)
Common stock repurchased, shares			342,740
Common stock repurchased	(20)		$ (20)
Shares issued—stock- based compensation (in shares)			(19,173)
Shares issued—stock-based compensation	0		$ 1	(1)	0
Stock-based compensation	6			6
Dividends declared	(32)				(32)
Distributions to noncontrolling interests	(22)						(22)
Ending balances at Jun. 30, 2019	6,259	$ 1	$ (390)	558	5,600	(50)	540
Ending balance, shares issued at Jun. 30, 2019		134,651,380
Ending balance, Treasury shares at Jun. 30, 2019			6,382,640
Beginning balances at Dec. 31, 2019	6,403	$ 1	$ (377)	553	5,757	(74)	543
Beginning balance, shares issued at Dec. 31, 2019		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2019			6,266,609
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation					145
Net income attributable to noncontrolling interests							12
Net income	157
Other comprehensive income	(32)					(32)	0
Common stock repurchased, shares			995,529
Common stock repurchased	(54)		$ (54)
Shares issued—stock- based compensation (in shares)			(282,476)
Shares issued—stock-based compensation	2		$ 18	(8)	(8)
Stock-based compensation	6			6
Dividends declared	(34)				(34)
Distributions to noncontrolling interests	(10)						(10)
Ending balances at Mar. 31, 2020	6,438	$ 1	$ (413)	551	5,860	(106)	545
Ending balance, shares issued at Mar. 31, 2020		134,651,380
Ending balance, Treasury shares at Mar. 31, 2020			6,979,662
Beginning balances at Dec. 31, 2019	6,403	$ 1	$ (377)	553	5,757	(74)	543
Beginning balance, shares issued at Dec. 31, 2019		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2019			6,266,609
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation	160
Net income attributable to noncontrolling interests	21
Net income	181
Other comprehensive income	(12)
Ending balances at Jun. 30, 2020	6,437	$ 1	$ (411)	558	5,840	(87)	536
Ending balance, shares issued at Jun. 30, 2020		134,651,380
Ending balance, Treasury shares at Jun. 30, 2020			6,963,331
Beginning balances at Mar. 31, 2020	6,438	$ 1	$ (413)	551	5,860	(106)	545
Beginning balance, shares issued at Mar. 31, 2020		134,651,380
Beginning balance, Treasury shares at Mar. 31, 2020			6,979,662
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation	15				15
Net income attributable to noncontrolling interests	9						9
Net income	24
Other comprehensive income	20					19	1
Shares issued—stock- based compensation (in shares)			(16,331)
Shares issued—stock-based compensation	0		$ 2	(1)	(1)
Stock-based compensation	8			8
Dividends declared	(34)				(34)
Distributions to noncontrolling interests	(19)						(19)
Ending balances at Jun. 30, 2020	$ 6,437	$ 1	$ (411)	$ 558	$ 5,840	$ (87)	$ 536
Ending balance, shares issued at Jun. 30, 2020		134,651,380
Ending balance, Treasury shares at Jun. 30, 2020			6,963,331