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Westlake Chemical Partners LP (Details) - USD ($) $ in Millions |  | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
Oct. 04, 2018 | Mar. 31, 2021 | Jun. 30, 2015
Related Party Transaction [Line Items] |  |  |
Partners' Capital Account, Units, Sold in Public Offering |  |  | 12,937,500
Partners' Units, Maximum Aggregate Offering Amount, ATM | $ 50 |  |
Westlake Chemical OpCo LP [Member] | Subsidiary of Common Parent [Member] | Limited Partner [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest |  | 22.80% |
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest |  | 77.20% |
Westlake Chemical Partners LP [Member] | Subsidiary of Common Parent [Member] | Limited Partner [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest |  | 40.10% |
Ownership interest (in units) |  | 14,122,230 |

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