Consolidated Statements Of Changes In Stockholders' Equity Statement - USD ($) $ in Millions	Total	Common Stock	Common Stock, Held in Treasury	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]
Beginning balances at Dec. 31, 2020	$ 6,578	$ 1	$ (401)	$ 569	$ 5,938	$ (64)	$ 535
Beginning balance, shares issued at Dec. 31, 2020		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2020			6,821,174
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	253				242		11
Other comprehensive income	(7)					(6)	(1)
Shares issued—stock- based compensation (in shares)			301,112
Shares issued—stock-based compensation	9		$ 22	(13)
Stock-based compensation	8			8
Dividends declared	(35)				(35)
Distributions to noncontrolling interests	(11)						(11)
Issuance of Westlake Chemical Partners LP common units	30						30
Ending balances at Mar. 31, 2021	6,825	$ 1	$ (379)	564	6,145	(70)	564
Ending balance, shares issued at Mar. 31, 2021		134,651,380
Ending balance, Treasury shares at Mar. 31, 2021			6,520,062
Beginning balances at Dec. 31, 2021	8,528	$ 1	$ (399)	581	7,808	(36)	573
Beginning balance, shares issued at Dec. 31, 2021		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2021			6,735,639
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	764				756		8
Other comprehensive income	(11)					(9)	(2)
Shares issued—stock- based compensation (in shares)		0	403,743
Shares issued—stock-based compensation	10	$ 0	$ 27	(17)	0
Stock-based compensation	8			8
Dividends declared	(39)				(39)
Distributions to noncontrolling interests	(10)						(10)
Issuance of Westlake Chemical Partners LP common units	2			0			2
Ending balances at Mar. 31, 2022	$ 9,252	$ 1	$ (372)	$ 572	$ 8,525	$ (45)	$ 571
Ending balance, shares issued at Mar. 31, 2022		134,651,380
Ending balance, Treasury shares at Mar. 31, 2022			6,331,896