Consolidated Statements of Operations (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Net sales	$ 3,055	$ 1,898	$ 8,271	$ 5,539
Cost of sales	2,037	1,650	5,872	4,839
Gross profit	1,018	248	2,399	700
Selling, general and administrative expenses	122	108	383	332
Amortization of intangibles	29	27	83	81
Restructuring, transaction and integration-related costs	6	34	6	36
Income from operations	861	79	1,927	251
Other income (expense)
Interest expense	(61)	(37)	(130)	(108)
Other income, net	13	12	35	32
Income before income taxes	813	54	1,832	175
Provision for (benefit from) income taxes	193	(15)	423	(75)
Net income	620	69	1,409	250
Net income attributable to noncontrolling interests	13	12	38	33
Net income attributable to Westlake Chemical Corporation	$ 607	$ 57	$ 1,371	$ 217
Earnings per common share attributable to Westlake Chemical Corporation:
Basic (in dollars per share)	$ 4.71	$ 0.45	$ 10.65	$ 1.69
Diluted (in dollars per share)	$ 4.69	$ 0.45	$ 10.60	$ 1.69
Weighted average common shares outstanding:
Basic (in shares)	128,060,193	127,701,340	128,053,337	127,872,434
Diluted (in shares)	128,765,814	127,953,907	128,710,097	128,073,066