Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Other comprehensive income (loss)	$ (40)	$ 53	$ (42)	$ 70
Net income	288	159	585	304
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Plan Amendments, Tax Effect [Abstract]
Amortization of benefits liability	0	1	0	1
Foreign Currency Translation Adjustment, by Component [Abstract]
Foreign currency translation	(37)	52	(43)	71
Income tax benefit (provision) on foreign currency translation	(3)	0	1	(2)
Comprehensive income	248	212	543	374
Comprehensive income attributable to noncontrolling interests, net of tax of $1 for the three months ended June 30, 2018 and 2017; and net of tax of $2 for the six months ended June 30, 2018 and 2017	6	7	18	15
Comprehensive income attributable to Westlake Chemical Corporation	$ 242	$ 205	$ 525	$ 359