Consolidated Statements Of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net sales	$ 8,118	$ 8,635	$ 8,041
Cost of sales	6,858	6,648	6,280
Gross profit	1,260	1,987	1,761
Selling, general and administrative expenses	458	445	399
Amortization of intangibles	109	101	108
Restructuring, transaction and integration-related costs	37	33	29
Income from operations	656	1,408	1,225
Other income (expense)
Interest expense	(124)	(126)	(159)
Other income, net	38	52	15
Income before income taxes	570	1,334	1,081
Provision for (benefit from) income taxes	108	300	(258)
Net income	462	1,034	1,339
Net income attributable to noncontrolling interests	41	38	35
Net income attributable to Westlake Chemical Corporation	$ 421	$ 996	$ 1,304
Earnings per common share attributable to Westlake Chemical Corporation:
Basic (in dollars per share)	$ 3.26	$ 7.66	$ 10.05
Diluted (in dollars per share)	$ 3.25	$ 7.62	$ 10.00
Weighted average common shares outstanding
Basic (in shares)	128,395,184	129,401,823	129,087,043
Diluted (in shares)	128,757,293	129,985,753	129,540,013