Consolidated Statements Of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 8,635	$ 8,041	$ 5,076
Cost of sales	6,648	6,280	4,093
Gross profit	1,987	1,761	983
Selling, general and administrative expenses	445	399	258
Amortization of intangibles	101	108	38
Transaction and integration-related costs	33	29	104
Income from operations	1,408	1,225	583
Other income (expense)
Interest expense	(126)	(159)	(79)
Other income, net	52	15	54
Income before income taxes	1,334	1,081	558
Provision for (benefit from) income taxes	300	(258)	138
Net income	1,034	1,339	420
Net income attributable to noncontrolling interests	38	35	21
Net income attributable to Westlake Chemical Corporation	$ 996	$ 1,304	$ 399
Earnings per common share attributable to Westlake Chemical Corporation:
Basic (in dollars per share)	$ 7.66	$ 10.05	$ 3.07
Diluted (in dollars per share)	$ 7.62	$ 10.00	$ 3.06
Weighted average shares outstanding
Basic (in shares)	129,401,823	129,087,043	129,367,712
Diluted (in shares)	129,985,753	129,540,013	129,974,822