Consolidated Statements of Operations (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Net sales	$ 1,898	$ 2,066	$ 5,539	$ 6,235
Cost of sales	1,650	1,695	4,839	5,225
Gross profit	248	371	700	1,010
Selling, general and administrative expenses	108	110	332	343
Amortization of intangibles	27	27	81	81
Restructuring, transaction and integration-related costs	34	8	36	32
Income from operations	79	226	251	554
Other income (expense)
Interest expense	(37)	(31)	(108)	(89)
Other income, net	12	21	32	32
Income before income taxes	54	216	175	497
Provision for (benefit from) income taxes	(15)	50	(75)	120
Net income	69	166	250	377
Net income attributable to noncontrolling interests	12	8	33	28
Net income attributable to Westlake Chemical Corporation	$ 57	$ 158	$ 217	$ 349
Earnings per common share attributable to Westlake Chemical Corporation:
Basic (in dollars per share)	$ 0.45	$ 1.22	$ 1.69	$ 2.70
Diluted (in dollars per share)	$ 0.45	$ 1.22	$ 1.69	$ 2.69
Weighted average common shares outstanding:
Basic (in shares)	127,701,340	128,216,105	127,872,434	128,408,841
Diluted (in shares)	127,953,907	128,552,360	128,073,066	128,770,944