Consolidated Statements of Operations (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net sales	$ 1,709	$ 2,144	$ 3,641	$ 4,169
Cost of sales	1,540	1,804	3,189	3,530
Gross profit	169	340	452	639
Selling, general and administrative expenses	104	117	224	233
Amortization of intangibles	27	27	54	54
Restructuring, transaction and integration-related costs	2	2	2	24
Income from operations	36	194	172	328
Other income (expense)
Interest expense	(40)	(28)	(71)	(58)
Other income, net	9	2	20	11
Income before income taxes	5	168	121	281
Provision for (benefit from) income taxes	(19)	39	(60)	70
Net income	24	129	181	211
Net income attributable to noncontrolling interests	9	10	21	20
Net income attributable to Westlake Chemical Corporation	$ 15	$ 119	$ 160	$ 191
Earnings per common share attributable to Westlake Chemical Corporation:
Basic (in dollars per share)	$ 0.11	$ 0.92	$ 1.24	$ 1.48
Diluted (in dollars per share)	$ 0.11	$ 0.92	$ 1.24	$ 1.47
Weighted average common shares outstanding:
Basic (in shares)	127,680,478	128,485,182	127,958,921	128,506,712
Diluted (in shares)	127,823,629	128,850,335	128,133,300	128,881,952