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Portion of the carrying amount as of the balance sheet date of obligations due all related parties that is payable after one year or beyond the normal operating cycle if longer.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Weighted average interest rate of long-term debt outstanding calculated at point in time.

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No definition available.

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Cash outflow related to the acquisition or continued holding of limited partnership interests held for investment purposes.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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The cash inflow from a long-term borrowing made from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth. Alternate caption: Proceeds from Advances from Affiliates.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Represents the consolidated leverage ratio required per the debt agreement during periods other than than one-year period following certain types of acquisitions

+ References

No definition available.

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Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Additional Ownership Interest

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No definition available.

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Represents the consolidated leverage ratio required per the debt agreement during any one-year period following certain acquisitions.

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No definition available.

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Long-Term Debt (Schedule of Long-term Debt) (Details) - USD ($) $ in Thousands			12 Months Ended
	Mar. 29, 2019	Apr. 29, 2015	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Aug. 01, 2017	Aug. 04, 2014
Related Party Transaction [Line Items]
Long-term debt			$ 399,674	$ 477,608
Proceeds from debt payable to Westlake			$ 123,511	$ 3,648	$ 165,257
Weighted average interest rate on all long-term debt			4.10%	4.40%
Senior Unsecured Revolving Credit Facility [Member] \| OpCo Revolver [Member]
Related Party Transaction [Line Items]
Long-term debt			$ 22,619	$ 224,064
Senior Unsecured Revolving Credit Facility [Member] \| MLP Revolver [Member]
Related Party Transaction [Line Items]
Long-term debt			$ 377,055	$ 253,544
Limited Partner [Member] \| Senior Unsecured Revolving Credit Facility [Member] \| OpCo Revolver [Member] \| LIBOR [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent			2.00%	2.00%
Minimum [Member] \| Limited Partner [Member] \| Line of Credit [Member] \| MLP Revolver [Member] \| LIBOR [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent			2.00%	2.00%
Westlake [Member] \| MLP Revolver [Member]
Related Party Transaction [Line Items]
Maximum borrowing capacity		$ 300,000				$ 600,000
Westlake [Member] \| Limited Partner [Member] \| OpCo Revolver [Member] \| Westlake Chemical OpCo LP [Member]
Related Party Transaction [Line Items]
Maximum borrowing capacity							$ 600,000
Westlake [Member] \| Limited Partner [Member] \| Line of Credit [Member] \| OpCo Revolver [Member] \| Westlake Chemical OpCo LP [Member] \| LIBOR [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent			2.00%
Westlake [Member] \| Limited Partner [Member] \| Line of Credit [Member] \| MLP Revolver [Member]
Related Party Transaction [Line Items]
Maximum consolidated leverage ratio during one year following acquisitions		5.50
Leverage capital ratio required during other periods		4.50
Westlake [Member] \| Minimum [Member] \| Limited Partner [Member] \| Line of Credit [Member] \| MLP Revolver [Member] \| LIBOR [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent		2.00%
Westlake [Member] \| Maximum [Member] \| Limited Partner [Member] \| Line of Credit [Member] \| MLP Revolver [Member] \| LIBOR [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent		3.00%
Westlake Chemical OpCo LP [Member] \| Affiliated Entity [Member]
Related Party Transaction [Line Items]
Additional ownership interest	4.50%	2.70%
Amount paid to purchase additional limited partner interest	$ 201,445	$ 135,341
Proceeds from debt payable to Westlake	$ 123,511