Consolidated Statements Of Changes In Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	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, 2016	$ 3,892	$ 1	$ (319)	$ 551	$ 3,412	$ (121)	$ 368
Beginning balance, shares issued at Dec. 31, 2016		134,651,380
Beginning balance, Treasury Stock, Shares at Dec. 31, 2016			5,726,377
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation	1,304				1,304
Net income attributable to noncontrolling interests	35						35
Net income	1,339
Other comprehensive income	133					128	5
Common stock repurchased, shares			0
Shares issued—stock- based compensation, shares		0	(493,502)
Shares issued—stock-based compensation	11	$ 0	$ 17	(6)
Stock-based compensation (in shares)			0
Stock-based compensation	14		$ 0	14
Dividends declared	(103)				(103)
Distributions to noncontrolling interests	(28)						(28)
Issuance of Westlake Chemical Partners LP common units	111			(4)			115
Ending balances at Dec. 31, 2017	5,369	$ 1	$ (302)	555	4,613	7	495
Ending balance, shares issued at Dec. 31, 2017		134,651,380
Ending balance, Treasury Stock, Shares at Dec. 31, 2017			5,232,875
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of certain tax effects to retained earnings	0				(13)	13
Net income attributable to Westlake Chemical Corporation	996				996
Net income attributable to noncontrolling interests	38						38
Net income	1,034
Other comprehensive income	(84)					(82)	(2)
Common stock repurchased, shares			1,368,881
Common stock repurchased	(106)		$ (106)				0
Shares issued—stock- based compensation, shares		0	(418,631)
Shares issued—stock-based compensation	9	$ 0	$ 26	(17)
Stock-based compensation (in shares)			0
Stock-based compensation	18		$ 0	18
Dividends declared	(120)				(120)
Distributions to noncontrolling interests	(45)						(45)
Ending balances at Dec. 31, 2018	$ 6,076	$ 1	$ (382)	556	5,477	(62)	486
Ending balance, shares issued at Dec. 31, 2018	134,651,380	134,651,380
Ending balance, Treasury Stock, Shares at Dec. 31, 2018	6,183,125		6,183,125
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 1				1
Net income attributable to Westlake Chemical Corporation	421				421
Net income attributable to noncontrolling interests	41						41
Net income	462
Other comprehensive income	(11)					(12)	1
Common stock repurchased, shares			517,712
Common stock repurchased	(30)		$ (30)				0
Shares issued—stock- based compensation, shares		0	(434,228)
Shares issued—stock-based compensation	$ 1	$ 0	$ 35	(25)	(9)
Stock-based compensation (in shares)	(18,635)		0
Stock-based compensation	$ 24		$ 0	24
Dividends declared	(132)				(132)
Distributions to noncontrolling interests	(50)						(50)
Issuance of Westlake Chemical Partners LP common units	63			(2)			65
Ending balances at Dec. 31, 2019	$ 6,403	$ 1	$ (377)	$ 553	$ 5,757	$ (74)	$ 543
Ending balance, shares issued at Dec. 31, 2019	134,651,380	134,651,380
Ending balance, Treasury Stock, Shares at Dec. 31, 2019	6,266,609		6,266,609