Consolidated Statements of Operations (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Net sales	$ 1,932	$ 2,025
Cost of sales	1,649	1,726
Gross profit	283	299
Selling, general and administrative expenses	120	116
Amortization of intangibles	27	27
Restructuring, transaction and integration-related costs	0	22
Income from operations	136	134
Other income (expense)
Interest expense	(31)	(30)
Other income, net	11	9
Income before income taxes	116	113
Provision for (benefit from) income taxes	(41)	31
Net income	157	82
Net income attributable to noncontrolling interests	12	10
Net income attributable to Westlake Chemical Corporation	$ 145	$ 72
Earnings per common share attributable to Westlake Chemical Corporation:
Basic (in dollars per share)	$ 1.13	$ 0.56
Diluted (in dollars per share)	$ 1.13	$ 0.55
Weighted average common shares outstanding:
Basic (in shares)	128,237,364	128,528,480
Diluted (in shares)	128,442,972	128,913,921