Consolidated Statements Of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 8,041	$ 5,076	$ 4,463
Cost of sales	6,272	4,095	3,278
Gross profit	1,769	981	1,185
Selling, general and administrative expenses	399	258	218
Amortization of intangibles	108	38	7
Transaction and integration-related costs	29	104	0
Income from operations	1,233	581	960
Other income (expense)
Interest expense	(159)	(79)	(35)
Other income, net	7	56	38
Income before income taxes	1,081	558	963
Provision for (benefit from) income taxes	(258)	138	298
Net income	1,339	420	665
Net income attributable to noncontrolling interests	35	21	19
Net income attributable to Westlake Chemical Corporation	$ 1,304	$ 399	$ 646
Earnings per common share attributable to Westlake Chemical Corporation:
Basic (in dollars per share)	$ 10.05	$ 3.07	$ 4.88
Diluted (in dollars per share)	$ 10.00	$ 3.06	$ 4.86
Weighted average shares outstanding
Basic (in shares)	129,087,043	129,367,712	131,823,707
Diluted (in shares)	129,540,013	129,974,822	132,301,812
Dividends per common share (in dollars per share)	$ 0.8012	$ 0.7442	$ 0.6930