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Westlake Chemical Partners LP (Details) - USD ($) $ / shares in Units, $ in Millions						3 Months Ended	12 Months Ended
	Oct. 04, 2018	Jul. 27, 2018	Sep. 29, 2017	Apr. 29, 2015	Aug. 04, 2014	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Partners' Units, Maximum Aggregate Offering Amount, ATM	$ 50
Related Party Transaction [Line Items]
Partners' Capital Account, Units, Sold in Public Offering			5,175,000		12,937,500
Sale of Unit Price Per Unit			$ 22.00		$ 24.00
Net proceeds from WLKP LP common stock units			$ 111		$ 286		$ 0	$ 111	$ 0
Payments of Stock Issuance Costs			$ 3		$ 24
Cash Distribution [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Incentive Distribution, Distribution Per Unit		$ 1.2938				$ 1.2938
Cash Distribution, Tranche One [Member] \| Unit Holders [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Maximum Percentage Of Income Distribution		85.00%				85.00%
Cash Distribution, Tranche One [Member] \| IDR Holders [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Maximum Percentage Of Income Distribution		15.00%				15.00%
Cash Distribution, Tranche Two [Member] \| Unit Holders [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Maximum Percentage Of Income Distribution		75.00%				75.00%
Cash Distribution, Tranche Two [Member] \| IDR Holders [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Maximum Percentage Of Income Distribution		25.00%				25.00%
Cash Distribution, Tranche Three [Member] \| Unit Holders [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Maximum Percentage Of Income Distribution		50.00%				50.00%
Cash Distribution, Tranche Three [Member] \| IDR Holders [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Maximum Percentage Of Income Distribution		50.00%				50.00%
Westlake Chemical OpCo LP [Member] \| Limited Partner [Member]
Related Party Transaction [Line Items]
Limited Partnership Ownership Percentage Increase			5.00%	2.70%
Subsidiary of Common Parent [Member] \| Westlake Chemical Partners LP [Member] \| IPO [Member] \| Limited Partner [Member]
Related Party Transaction [Line Items]
Limited partner interest (percent)					47.80%		43.80%
Subsidiary of Common Parent [Member] \| Westlake Chemical OpCo LP [Member] \| IPO [Member] \| Limited Partner [Member]
Related Party Transaction [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest					10.60%		18.30%
Limited partner interest (percent)					89.40%		81.70%
Minimum [Member] \| Cash Distribution, Tranche One [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Incentive Distribution Rights, Target Distribution Per Unit Requiring Marginal Percentage Distribution to IDR Holders		$ 1.2938				$ 0.3163
Minimum [Member] \| Cash Distribution, Tranche Two [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Incentive Distribution Rights, Target Distribution Per Unit Requiring Marginal Percentage Distribution to IDR Holders		1.4063				0.3438
Minimum [Member] \| Cash Distribution, Tranche Three [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Incentive Distribution Rights, Target Distribution Per Unit Requiring Marginal Percentage Distribution to IDR Holders		1.6875				0.4125
Maximum [Member] \| Cash Distribution, Tranche One [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Incentive Distribution Rights, Target Distribution Per Unit Requiring Marginal Percentage Distribution to IDR Holders		1.4063				0.3438
Maximum [Member] \| Cash Distribution, Tranche Two [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Incentive Distribution Rights, Target Distribution Per Unit Requiring Marginal Percentage Distribution to IDR Holders		$ 1.6875				$ 0.4125