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				72
Net income attributable to noncontrolling interests	10						10
Net income	82
Other comprehensive income (loss)	(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, 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				145
Net income attributable to noncontrolling interests	12						12
Net income	157
Other comprehensive income (loss)	(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