Westlake Chemical Partners (WLKP) 10-Q 2 May 24 2024 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2024	Apr. 25, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
Document Transition Report	false
Entity File Number	001-36567
Entity Registrant Name	Westlake Chemical Partners LP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	32-0436529
Entity Address, Address Line One	2801 Post Oak Boulevard
Entity Address, Address Line Two	Suite 600
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77056
City Area Code	713
Local Phone Number	585-2900
Title of 12(b) Security	Common units representing limited partnership interests
Trading Symbol	WLKP
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Units, Units Outstanding		35,228,134
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001604665

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets
Cash and cash equivalents	$ 55,760	$ 58,619
Receivable under the Investment Management Agreement—Westlake Corporation ("Westlake")	94,477	94,444
Receivables, Net, Current	27,228	18,701
Inventories	4,860	4,432
Prepaid expenses and other current assets	257	442
Total current assets	224,348	226,203
Property, plant and equipment, net	926,813	943,843
Goodwill	5,814	5,814
Deferred charges and other assets, net	138,101	140,982
Total assets	1,295,076	1,316,842
Current liabilities
Accrued and other liabilities	19,801	24,980
Total current liabilities	43,083	56,335
Deferred income taxes	1,664	1,632
Other liabilities	2,410	2,951
Total liabilities	446,831	460,592
Commitments and contingencies (Note 12)
EQUITY
Total Westlake Chemical Partners LP partners' capital	278,160	279,934
Noncontrolling interest in Westlake Chemical OpCo LP ("OpCo")	570,085	576,316
Total equity	848,245	856,250
Total liabilities and equity	1,295,076	1,316,842
Publicly and Privately Held | Common units
EQUITY
Common unitholders	472,450	473,513
Westlake
EQUITY
General partner—Westlake	(242,572)	(242,572)
Westlake | Common units
EQUITY
Common unitholders	48,282	48,993
Affiliated Entity
Current assets
Accounts receivable, net	41,766	49,565
Current liabilities
Accounts payable	8,439	15,166
Affiliated Entity | Westlake
Current liabilities
Long-term debt payable to Westlake	399,674	399,674
Nonrelated Party
Current assets
Receivables, Net, Current	27,228	18,701
Current liabilities
Accounts payable	$ 14,843	$ 16,189

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - Common units - shares	Mar. 31, 2024	Dec. 31, 2023
Publicly and Privately Held
Units issued (in shares)	21,105,904	21,105,904
Units outstanding (in shares)	21,105,904	21,105,904
Westlake
Units issued (in shares)	14,122,230	14,122,230
Units outstanding (in shares)	14,122,230	14,122,230

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Total net sales	$ 284,673	$ 307,677
Cost of sales	182,493	201,604
Gross profit	102,180	106,073
Selling, general and administrative expenses	7,077	7,914
Income from operations	95,103	98,159
Other income (expense)
Other income, net	1,334	820
Income before income taxes	89,856	91,664
Provision for income taxes	210	212
Net income	89,646	91,452
Less: Net income attributable to noncontrolling interest in OpCo	74,813	76,560
Net income attributable to Westlake Chemical Partners LP and limited partners' interest in net income	$ 14,833	$ 14,892
Net income per limited partner unit attributable to Westlake Chemical Partners LP (basic and diluted)
Weighted average limited partner units outstanding (basic and diluted) (in units)	35,228,134	35,221,868
Common units
Other income (expense)
Net income attributable to Westlake Chemical Partners LP and limited partners' interest in net income	$ 14,833	$ 14,892
Net income per limited partner unit attributable to Westlake Chemical Partners LP (basic and diluted)
Common units (in usd per share)	$ 0.42	$ 0.42
Diluted (in usd per share)	$ 0.42	$ 0.42
Weighted average limited partner units outstanding (basic and diluted) (in units)	35,228,134	35,221,868
Common units | Westlake
Net income per limited partner unit attributable to Westlake Chemical Partners LP (basic and diluted)
Weighted average limited partner units outstanding (basic and diluted) (in units)	14,122,230	14,122,230
Publicly and Privately Held | Common units
Net income per limited partner unit attributable to Westlake Chemical Partners LP (basic and diluted)
Weighted average limited partner units outstanding (basic and diluted) (in units)	21,105,904	21,099,638
Affiliated Entity
Net co-products, ethylene and other sales—third parties	$ 235,209	$ 257,471
Affiliated Entity | Westlake
Selling, general and administrative expenses	6,099	6,671
Other income (expense)
Interest expense	(6,581)	(7,315)
Nonrelated Party
Net co-products, ethylene and other sales—third parties	$ 49,464	$ 50,206

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Noncontrolling Interest in OpCo	Westlake General Partner	Common units Publicly and Privately Held Limited Partner	Common units Westlake Limited Partner
Total equity at Dec. 31, 2022	$ 903,708	$ 611,778	$ (242,572)	$ 480,643	$ 53,859
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	91,452	76,560	0	8,921	5,971
Distribution to unitholders	(16,604)	0	0	(9,947)	(6,657)
Distribution to noncontrolling interest retained in OpCo by Westlake	(88,678)	(88,678)	0	0	0
Total equity at Mar. 31, 2023	889,878	599,660	(242,572)	479,617	53,173
Total equity at Dec. 31, 2023	856,250	576,316	(242,572)	473,513	48,993
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	89,646	74,813	0	8,887	5,946
Distribution to unitholders	(16,607)	0	0	(9,950)	(6,657)
Distribution to noncontrolling interest retained in OpCo by Westlake	(81,044)	(81,044)	0	0	0
Total equity at Mar. 31, 2024	$ 848,245	$ 570,085	$ (242,572)	$ 472,450	$ 48,282

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities
Net income	$ 89,646	$ 91,452
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	27,994	26,636
Loss from disposition of property, plant and equipment	271	367
Other losses, net	256	575
Changes in operating assets and liabilities
Accounts receivable—third parties	(8,751)	(248)
Net accounts receivable—Westlake	3,720	20,904
Inventories	(428)	(751)
Prepaid expenses and other current assets	185	152
Accounts payable—third parties	(1,173)	2,791
Accrued and other liabilities	(3,231)	5,467
Other, net	(3,924)	(2,485)
Net cash provided by operating activities	104,565	144,860
Cash flows from investing activities
Additions to property, plant and equipment	(9,773)	(12,656)
Investments with Westlake under the Investment Management Agreement	0	(90,116)
Maturities of investments with Westlake under the Investment Management Agreement	0	103,000
Net cash provided by (used for) investing activities	(9,773)	228
Cash flows from financing activities
Proceeds from debt payable to Westlake	54,000	39,000
Repayment of debt payable to Westlake	(54,000)	(39,000)
Distributions to unitholders	(16,607)	(16,604)
Net cash used for financing activities	(97,651)	(105,282)
Net increase (decrease) in cash and cash equivalents	(2,859)	39,806
Cash and cash equivalents at beginning of period	58,619	64,782
Cash and cash equivalents at end of period	55,760	104,588
Payments of Ordinary Dividends, Noncontrolling Interest	$ (81,044)	$ (88,678)

Description of Business and Bas

Description of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation Description of Business Westlake Chemical Partners LP (the "Partnership") is a Delaware limited partnership formed in March 2014 to operate, acquire and develop ethylene production facilities and related assets. On August 4, 2014, the Partnership completed its initial public offering (the "IPO") of 12,937,500 common units representing limited partner interests. In connection with the IPO, the Partnership acquired a 10.6% limited partner interest in Westlake Chemical OpCo LP ("OpCo") and a 100% interest in Westlake Chemical OpCo GP LLC ("OpCo GP"), which is the general partner of OpCo. OpCo owns three ethylene production facilities and one common carrier ethylene pipeline (collectively, the "Contributed Assets"). Since the IPO, the Partnership has periodically purchased additional limited partner interest in OpCo. Most recently, on March 29, 2019, the Partnership purchased an additional 4.5% newly-issued limited partner interest in OpCo for approximately $201,445, resulting in an aggregate 22.8% limited partner interest in OpCo, effective January 1, 2019. The remaining 77.2% limited partner interest in OpCo is owned by Westlake Corporation. Basis of Presentation The accompanying unaudited consolidated interim financial statements were prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the "SEC") for interim periods. Accordingly, certain information and footnotes required for complete financial statements under generally accepted accounting principles in the United States ("U.S. GAAP") have not been included. These interim consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto of the Partnership included in the annual report on Form 10-K for the fiscal year ended December 31, 2023 (the "2023 Form 10-K"), filed with the SEC on February 28, 2024. These financial statements have been prepared in conformity with the accounting principles and practices as disclosed in the notes to the consolidated financial statements of the Partnership for the fiscal year ended December 31, 2023. References to "Westlake" refer collectively to Westlake Corporation and its subsidiaries, other than the Partnership, OpCo and OpCo GP. The Partnership holds a 22.8% limited partner interest and the entire non-economic general partner interest in OpCo. The remaining 77.2% limited partner interest in OpCo is owned directly by Westlake, which has no rights to direct the activities that most significantly impact the economic performance of OpCo. As a result of the fact that substantially all of OpCo's activities are conducted on behalf of Westlake, and the fact that OpCo exhibits disproportionality of voting rights to economic interest, OpCo was deemed to be a variable interest entity. The Partnership, through its ownership of OpCo's general partner, has the power to direct the activities that most significantly impact the economic performance of OpCo, and it also has the obligation or right to absorb losses or receive benefits from OpCo that could potentially be significant to OpCo. As such, the Partnership was determined to be OpCo's primary beneficiary and therefore consolidates OpCo's results of operations and financial position. Westlake's retained interest of 77.2% is recorded as noncontrolling interest in the Partnership's consolidated financial statements. In the opinion of the Partnership's management, the accompanying unaudited consolidated interim financial statements reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Partnership's financial position as of March 31, 2024, its results of operations for the three months ended March 31, 2024 and 2023 and the changes in its cash position for the three months ended March 31, 2024 and 2023. Results of operations and changes in cash position for the interim periods presented are not necessarily indicative of the results that will be realized for the fiscal year ending December 31, 2024 or any other interim period. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Actual results could differ materially from those estimates. Recently Issued Accounting Pronouncement Income Taxes (ASU No. 2023-09) In December 2023, the FASB issued an accounting standards update to require additional tax disclosures under Topic 740 primarily related to the rate reconciliation and income taxes paid disclosures. The amendments in this update will be effective for fiscal years beginning after December 15, 2024 and are to be applied on a prospective basis. Retrospective application is also permitted. The update is not expected to have a material impact on the Partnership's disclosures. Recently Adopted Accounting Standards Segment Reporting (ASU No. 2023-07) In November 2023, the Financial Accounting Standards Board ("FASB") issued an accounting standards update. The update requires public entities to disclose on an annual and interim basis, significant segment expenses that are regularly provided to the chief operating decision maker ("CODM"), the title and position of the CODM and an explanation of how the CODM uses the reported measure(s) of segment profit or loss in assessing segment performance and deciding how to allocate resources. The update also requires that a public entity that has a single reportable segment provide all disclosures required by the update as well as all existing segment disclosures in Topic 280. The amendments in this update will be effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024 and are to be applied retrospectively to all prior periods presented in the financial statements. Early adoption is permitted. The Partnership adopted this accounting standard effective January 1, 2024, and the adoption will result in additional segment disclosures in the Partnership's annual financial statements for the year ending December 31, 2024 and the interim periods thereafter.

Accounts Receivable_Third Parti

Accounts Receivable—Third Parties	3 Months Ended
	Mar. 31, 2024
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Accounts Receivable—Third Parties	Accounts Receivable—Third Parties Accounts receivable—third parties consist of the following: March 31, December 31, Trade customers $ 24,306 $ 15,622 Allowance for credit losses (435) (278) Other receivables 3,357 3,357 Accounts receivable, net—third parties $ 27,228 $ 18,701

Inventories

Inventories	3 Months Ended
	Mar. 31, 2024
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consist of the following: March 31, December 31, Finished products $ 4,375 $ 4,147 Feedstock, additives and chemicals 485 285 Inventories $ 4,860 $ 4,432

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment Depreciation expense on property, plant and equipment of $21,537 and $20,957 is included in cost of sales in the consolidated statements of operations for the three months ended March 31, 2024 and 2023, respectively.

Deferred Charges and Other Asse

Deferred Charges and Other Assets	3 Months Ended
	Mar. 31, 2024
Other Assets, Noncurrent [Abstract]
Deferred Charges and Other Assets	Deferred Charges and Other Assets Amortization expense on deferred charges and other assets of $6,457 and $5,679 is included in cost of sales in the consolidated statements of operations for the three months ended March 31, 2024 and 2023, respectively

Distributions and Net Income Pe

Distributions and Net Income Per Limited Partner Unit	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Distributions and Net Income Per Limited Partner Unit	Distributions and Net Income Per Limited Partner Unit On April 30, 2024, the board of directors of Westlake Chemical Partners GP LLC ("Westlake GP"), the Partnership's general partner, declared a quarterly cash distribution for the three months ended March 31, 2024 of $0.4714 per unit. This distribution is payable on May 29, 2024 to unitholders of record as of May 13, 2024. Distributions are declared subsequent to quarter end; therefore, the table below represents total cash distributions declared from earnings of the related periods pertaining to such distributions. Three Months Ended March 31, 2024 2023 Net income attributable to the Partnership $ 14,833 $ 14,892 Less: Limited partners' distribution declared on common units 16,607 16,603 Distribution in excess of net income $ (1,774) $ (1,711) Net income per unit applicable to common limited partner units is computed by dividing the respective limited partners' interest in net income by the weighted-average number of common units outstanding for the period. Because the Partnership has more than one class of participating securities, it uses the two-class method when calculating the net income per unit applicable to limited partners. The classes of participating securities include common units and incentive distribution rights. Net income attributable to the Partnership is allocated to the unitholders in accordance with their respective ownership percentages in preparation of the consolidated statements of changes in equity. However, when distributions related to the incentive distribution rights are made, net income equal to the amount of those distributions is first allocated to the general partner before the remaining net income is allocated to the unitholders based on their respective ownership percentages. Basic and diluted net income per unit is the same because the Partnership does not have any potentially dilutive units outstanding for the periods presented. Three Months Ended March 31, 2024 Limited Partners' Common Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution $ 16,607 $ — $ 16,607 Distribution in excess of net income (1,774) — (1,774) Net income $ 14,833 $ — $ 14,833 Weighted average units outstanding: Basic and diluted 35,228,134 35,228,134 Net income per limited partner unit: Basic and diluted $ 0.42 Three Months Ended March 31, 2023 Limited Partners' Common Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution $ 16,603 $ — $ 16,603 Distribution in excess of net income (1,711) — (1,711) Net income $ 14,892 $ — $ 14,892 Weighted average units outstanding: Basic and diluted 35,221,868 35,221,868 Net income per limited partner unit: Basic and diluted $ 0.42 The amended Partnership Agreement provides that the Partnership will distribute cash that is deemed to be an appropriate portion of the Partnership's total operating surplus. If cash distributions to the Partnership's unitholders exceed $1.2938 per common unit in any quarter, the Partnership's unitholders and Westlake, as the holder of the Partnership's incentive distribution rights, will receive distributions according to the following percentage allocations: Marginal Percentage Interest in Distributions Total Quarterly Distribution Per Unit Unitholders IDR Holders Above $1.2938 up to $1.4063 85.0 % 15.0 % Above $1.4063 up to $1.6875 75.0 % 25.0 % Above $1.6875 50.0 % 50.0 % The Partnership's distribution for the three months ended March 31, 2024 did not exceed the $1.2938 per unit threshold, and, as a result, no distribution was made with respect to the Partnership's incentive distribution rights to Westlake, as the holder of the Partnership's incentive distribution rights. Distributions Per Common Unit Distributions per common unit for the three months ended March 31, 2024 and 2023 were as follows: Three Months Ended March 31, 2024 2023 Distributions per common unit $ 0.4714 $ 0.4714

Partners' Equity

Partners' Equity	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Partners' Equity	Partners' Equity On October 4, 2018, the Partnership and Westlake Chemical Partners GP LLC, the general partner of the Partnership, entered into an Equity Distribution Agreement with UBS Securities LLC, Barclays Capital Inc., Citigroup Global Markets Inc., Deutsche Bank Securities Inc., RBC Capital Markets, LLC, Merrill Lynch, Pierce, Fenner & Smith Incorporated and Wells Fargo Securities, LLC to offer and sell the Partnership's common units, from time to time, up to an aggregate offering amount of $50,000. The Equity Distribution Agreement was amended on February 28, 2020 to reference a new shelf registration and subsequent renewals thereof for utilization under this agreement. No common units were issued under this program as of March 31, 2024. On March 29, 2019, the Partnership completed the issuance and sale of 2,940,818 common units at a price of $21.40 per unit through a private placement. TTWF LP, Westlake's principal stockholder and a related party, acquired 1,401,869 common units out of 2,940,818 common units issued in the private placement.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2024
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Related party transactions between the Partnership, OpCo and Westlake are primarily based on agreements such as the Ethylene Sales Agreement, the Feedstock Supply Agreement, the Services and Secondment Agreement, Site Lease Agreements, the Omnibus Agreement, the Investment Management Agreement, the Exchange Agreement, the OpCo Partnership Agreement, the OpCo Revolver and the MLP Revolver. These agreements, discussed in detail in the Partnership's 2023 consolidated financial statements included in the 2023 Form 10-K filed on February 28, 2024, reflect the pervasive effect of the relationship with Westlake on the Partnership's operations and its consolidated financial statements. Pursuant to these agreements, the Partnership and OpCo regularly enter into transactions with Westlake. See below for descriptions and details of significant related party transactions. Sales to Related Parties OpCo sells ethylene to Westlake under the Ethylene Sales Agreement. Additionally, the Partnership and OpCo from time to time provide other services or products for which it charges Westlake a fee. Sales to related parties were as follows: Three Months Ended March 31, 2024 2023 Net sales—Westlake $ 235,209 $ 257,471 Cost of Sales from Related Parties Charges for goods and services purchased by the Partnership and OpCo from Westlake and included in cost of sales relate primarily to feedstock purchased under the Feedstock Supply Agreement and services provided under the Services and Secondment Agreement. Charges from related parties in cost of sales were as follows: Three Months Ended March 31, 2024 2023 Feedstock purchased from Westlake and included in cost of sales $ 78,537 $ 103,042 Other charges from Westlake and included in cost of sales 32,068 30,906 Total $ 110,605 $ 133,948 Services from Related Parties Included in Selling, General and Administrative Expenses Charges for services purchased by the Partnership from Westlake and included in selling, general and administrative expenses primarily relate to services Westlake performs on behalf of the Partnership under the Omnibus Agreement, including the Partnership's finance, legal, information technology, human resources, communication, ethics and compliance and other administrative functions. Charges from related parties included within selling, general and administrative expenses were as follows: Three Months Ended March 31, 2024 2023 Services received from Westlake and included in selling, general and administrative expenses $ 6,099 $ 6,671 Goods and Services from Related Parties Capitalized as Assets Charges for goods and services purchased by the Partnership and OpCo from Westlake which were capitalized as assets relate primarily to the services of Westlake employees under the Services and Secondment Agreement. Charges from related parties for goods and services capitalized as assets were as follows: Three Months Ended March 31, 2024 2023 Goods and services purchased from Westlake and capitalized as assets $ 412 $ 699 Receivable under the Investment Management Agreement On August 1, 2017, the Partnership, OpCo and Westlake executed an investment management agreement (the "Investment Management Agreement") that authorized Westlake to invest the Partnership's and OpCo's excess cash with Westlake for durations of up to a maximum of nine months. Per the terms of the Investment Management Agreement, the Partnership earns a market return plus five basis points and Westlake provides daily availability of the invested cash to meet any liquidity needs of the Partnership or OpCo. Accrued interest of $1,305 and $1,272 was included in the receivable under the Investment Management Agreement balance at March 31, 2024 and December 31, 2023, respectively. Total interest earned related to the Investment Management Agreement was $1,305 and $907 for the three months ended March 31, 2024 and 2023, respectively. The Partnership's receivable under the Investment Management Agreement was as follows: March 31, December 31, Receivable under the Investment Management Agreement $ 94,477 $ 94,444 Accounts Receivable from Related Parties The Partnership's accounts receivable from Westlake result primarily from ethylene sales to Westlake and the buyer deficiency fee and shortfall fee recognized under the Ethylene Sales Agreement. As a result of force majeure events in 2021, the Partnership recognized a shortfall fee of $58,906 during 2021, of which $189 remained to be collected by the Partnership as of December 31, 2023 and was received in the three months ended March 31, 2024. The Partnership's accounts receivable from Westlake were as follows: March 31, December 31, Accounts receivable—Westlake $ 41,766 $ 49,565 Accounts Payable to Related Parties The Partnership's accounts payable to Westlake result primarily from feedstock purchases under the Feedstock Supply Agreement and services provided under the Services and Secondment Agreement and the Omnibus Agreement. The Partnership's accounts payable to Westlake were as follows: March 31, December 31, Accounts payable—Westlake $ 8,439 $ 15,166 Related Party Leases OpCo is obligated to Westlake under various long-term and short-term noncancelable operating leases, primarily related to rail cars and land. Operating lease rentals paid to Westlake for such leases were $425 and $737 for the three months ended March 31, 2024 and 2023, respectively, an d are reflected in other charges from Westlake that are included in cost of sales. OpCo has two site lease agreements with Westlake, each of which has a term of 50 years. Pursuant to the site lease agreements, OpCo pays Westlake one dollar per site per year. Debt Payable to Related Parties See Note 9 for a description of related party debt payable balances. Interest on related party debt payable balances, net of capitalized interest, for the three months ended March 31, 2024 and 2023 was $6,581 and $7,315 , respecti vely. Interest on related party debt payable is presented as interest expense—Westlake in the consolidated statements of operations. At March 31, 2024 and December 31, 2023, accrued interest on related party debt was $6,617 and $6,675, respectively, and is reflected as a component of accrued and other liabilities in the consolidated balance sheets. Debt payable to related parties was as follows: March 31, December 31, Long-term debt payable to Westlake $ 399,674 $ 399,674 Major Customer and Concentration of Credit Risk During the three months ended March 31, 2024 and 2023, Westlake accounted for approximately 82.6% and 83.7%, respectively, of the Partnership's net sale

Long-term Debt Payable to Westl

Long-term Debt Payable to Westlake	3 Months Ended
	Mar. 31, 2024
Related Party Transactions [Abstract]
Long-term Debt Payable to Westlake	Long-Term Debt Payable to Westlake Long-term debt payable to Westlake consists of the following: March 31, December 31, OpCo Revolver $ 22,619 $ 22,619 MLP Revolver 377,055 377,055 Long-term debt payable to Westlake $ 399,674 $ 399,674 As of March 31, 2024, outstanding borrowings under the OpCo Revolver and the MLP Revolver bore interest at the Secured Overnight Financing Rate, as administered by the Federal Reserve Bank of New York ("SOFR") plus the Applicable Margin plus a 0.10% credit spread adjustment. The Applicable Margin under the OpCo Revolver is 1.75%. The Applicable Margin under the MLP Revolver varies between 1.75% and 2.75%, depending on the Partnership's Consolidated Leverage Ratio. The OpCo Revolver and the MLP Revolver are scheduled to mature on July 12, 2027. The weighted average interest rate on all long-term debt was 7.2% and 7.2% at March 31, 2024 and December 31, 2023, respectively. As of March 31, 2024, the Partnership was in compliance with all of the covenants under the OpCo Revolver and the MLP Revolver.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Partnership reports certain assets and liabilities at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). Under the accounting guidance for fair value measurements, inputs used to measure fair value are classified in one of three levels: Level 1: Quoted market prices in active markets for identical assets or liabilities. Level 2: Observable market-based inputs or unobservable inputs that are corroborated by market data. Level 3: Unobservable inputs that are not corroborated by market data. The Partnership has financial assets and liabilities subject to fair value measures. These financial assets and liabilities include cash and cash equivalents, accounts receivable, net, accounts payable and long-term debt payable to Westlake, all of which are recorded at carrying value. The amounts reported in the consolidated balance sheets for accounts receivable, net and accounts payable approximate their fair value due to the short maturities of these instruments. The carrying and fair values of the Partnership's long-term debt at March 31, 2024 and December 31, 2023 are summarized in the table below. The fair value of long-term debt is determined based on the present value of expected future cash flows using a discounted cash flow methodology. Because the Partnership's valuation methodology used for long-term debt requires the use of significant unobservable inputs, the inputs used to measure the fair value of the Partnership's long-term debt are classified as Level 3 within the fair value hierarchy. Inputs used to estimate the fair values of the Partnership's long-term debt include the selection of an appropriate discount rate. March 31, 2024 December 31, 2023 Carrying Fair Carrying Fair Long-term debt payable to Westlake $ 399,674 $ 413,825 $ 399,674 $ 408,110

Supplemental Information

Supplemental Information	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Information	Supplemental Information Accrued and Other Liabilities Accrued and other liabilities were $19,801 and $24,980 at March 31, 2024 and December 31, 2023, respectively. Accrued maintenance expense, accrued capital expenditures, accrued interest on related party debt and accrued taxes, which are components of accrued and other liabilities, were $2,743, $2,310, $6,617 and $3,439, respectively, at March 31, 2024 and $5,170, $4,627, $6,675 and $3,033, respectively, at December 31, 2023. No other component of accrued and other liabilities was more than five percent of total current liabilities. Cash Flow Information Non-cash Investing Activity Capital expenditure related liabilities, included in accounts payable—third parties and accrued and other liabilities, were $5,495 and $2,091 at March 31, 2024 and 2023, respectively. Interest Paid Interest paid by the Partnership, net of interest capitalized, was $6,640 and $4,696 for the three months ended March 31, 2024 and 2023, respectively. Operating Leases Right-of-use assets obtained in exchange for operating lease obligations were $0 and $5,079 at March 31, 2024 and December 31, 2023, respectively.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Partnership is subject to environmental laws and regulations that can impose civil and criminal sanctions and that may require the Partnership to mitigate the effects of contamination caused by the release or disposal of hazardous substances into the environment. These laws include the federal Clean Air Act, the federal Water Pollution Control Act, the Resource Conservation and Recovery Act, the Comprehensive Environmental Response, Compensation, and Liability Act ("CERCLA"), the Toxic Substances Control Act and various other federal, state and local laws and regulations. Under CERCLA, an owner or operator of property may be held strictly liable for remediating contamination without regard to whether that person caused the contamination, and without regard to whether the practices that resulted in the contamination were legal at the time they occurred. Because the Partnership's production sites have a history of industrial use, it is impossible to predict precisely what effect these legal requirements will have on the Partnership. Pursuant to the Omnibus Agreement, certain subsidiaries of Westlake will indemnify the Partnership for liabilities that occurred or existed prior to August 4, 2014. In September 2021, shortly after the turnaround on OpCo's Petro 2 facility commenced, there was a flash fire at the quench tower of the Petro 2 facility. Contractors and employees working on and near the quench tower were injured and multiple lawsuits were filed against Westlake and OpCo. Final settlements were reached with all of the plaintiffs to fully resolve the lawsuits by Westlake, but payment by the insurance carriers has not yet been completed. Westlake and its subsidiaries are responsible for indemnifying the Partnership in connection with any losses incurred by OpCo as a result of the fire. The Partnership is also involved in other legal proceedings incidental to the conduct of its business. After considering all relevant facts and circumstances, including applicable insurance and indemnification by Westlake, the Partnership does not believe that any of these legal proceedings will have a material adverse effect on its financial condition, results of operations or cash flows.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net income	$ 14,833	$ 14,892

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Mar. 31, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Description of Business and B_2

Description of Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated interim financial statements were prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the "SEC") for interim periods. Accordingly, certain information and footnotes required for complete financial statements under generally accepted accounting principles in the United States ("U.S. GAAP") have not been included. These interim consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto of the Partnership included in the annual report on Form 10-K for the fiscal year ended December 31, 2023 (the "2023 Form 10-K"), filed with the SEC on February 28, 2024. These financial statements have been prepared in conformity with the accounting principles and practices as disclosed in the notes to the consolidated financial statements of the Partnership for the fiscal year ended December 31, 2023. References to "Westlake" refer collectively to Westlake Corporation and its subsidiaries, other than the Partnership, OpCo and OpCo GP. The Partnership holds a 22.8% limited partner interest and the entire non-economic general partner interest in OpCo. The remaining 77.2% limited partner interest in OpCo is owned directly by Westlake, which has no rights to direct the activities that most significantly impact the economic performance of OpCo. As a result of the fact that substantially all of OpCo's activities are conducted on behalf of Westlake, and the fact that OpCo exhibits disproportionality of voting rights to economic interest, OpCo was deemed to be a variable interest entity. The Partnership, through its ownership of OpCo's general partner, has the power to direct the activities that most significantly impact the economic performance of OpCo, and it also has the obligation or right to absorb losses or receive benefits from OpCo that could potentially be significant to OpCo. As such, the Partnership was determined to be OpCo's primary beneficiary and therefore consolidates OpCo's results of operations and financial position. Westlake's retained interest of 77.2% is recorded as noncontrolling interest in the Partnership's consolidated financial statements. In the opinion of the Partnership's management, the accompanying unaudited consolidated interim financial statements reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Partnership's financial position as of March 31, 2024, its results of operations for the three months ended March 31, 2024 and 2023 and the changes in its cash position for the three months ended March 31, 2024 and 2023. Results of operations and changes in cash position for the interim periods presented are not necessarily indicative of the results that will be realized for the fiscal year ending December 31, 2024 or any other interim period. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Actual results could differ materially from those estimates.
Recently Issued Accounting Pronouncement and Recently Adopted Accounting Standards	Recently Issued Accounting Pronouncement Income Taxes (ASU No. 2023-09) In December 2023, the FASB issued an accounting standards update to require additional tax disclosures under Topic 740 primarily related to the rate reconciliation and income taxes paid disclosures. The amendments in this update will be effective for fiscal years beginning after December 15, 2024 and are to be applied on a prospective basis. Retrospective application is also permitted. The update is not expected to have a material impact on the Partnership's disclosures. Recently Adopted Accounting Standards Segment Reporting (ASU No. 2023-07) In November 2023, the Financial Accounting Standards Board ("FASB") issued an accounting standards update. The update requires public entities to disclose on an annual and interim basis, significant segment expenses that are regularly provided to the chief operating decision maker ("CODM"), the title and position of the CODM and an explanation of how the CODM uses the reported measure(s) of segment profit or loss in assessing segment performance and deciding how to allocate resources. The update also requires that a public entity that has a single reportable segment provide all disclosures required by the update as well as all existing segment disclosures in Topic 280. The amendments in this update will be effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024 and are to be applied retrospectively to all prior periods presented in the financial statements. Early adoption is permitted. The Partnership adopted this accounting standard effective January 1, 2024, and the adoption will result in additional segment disclosures in the Partnership's annual financial statements for the year ending December 31, 2024 and the interim periods thereafter.

Accounts Receivable_Third Par_2

Accounts Receivable—Third Parties (Tables)	3 Months Ended
	Mar. 31, 2024
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable	Accounts receivable—third parties consist of the following: March 31, December 31, Trade customers $ 24,306 $ 15,622 Allowance for credit losses (435) (278) Other receivables 3,357 3,357 Accounts receivable, net—third parties $ 27,228 $ 18,701

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2024
Inventory Disclosure [Abstract]
Schedule Of Inventory	Inventories consist of the following: March 31, December 31, Finished products $ 4,375 $ 4,147 Feedstock, additives and chemicals 485 285 Inventories $ 4,860 $ 4,432

Distributions and Net Income _2

Distributions and Net Income Per Limited Partner Unit (Tables)	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Schedule of Incentive Distributions Made to Managing Members or General Partners by Distribution	Distributions are declared subsequent to quarter end; therefore, the table below represents total cash distributions declared from earnings of the related periods pertaining to such distributions. Three Months Ended March 31, 2024 2023 Net income attributable to the Partnership $ 14,833 $ 14,892 Less: Limited partners' distribution declared on common units 16,607 16,603 Distribution in excess of net income $ (1,774) $ (1,711)
Schedule of Earnings Per Share, Basic and Diluted	Net income per unit applicable to common limited partner units is computed by dividing the respective limited partners' interest in net income by the weighted-average number of common units outstanding for the period. Because the Partnership has more than one class of participating securities, it uses the two-class method when calculating the net income per unit applicable to limited partners. The classes of participating securities include common units and incentive distribution rights. Net income attributable to the Partnership is allocated to the unitholders in accordance with their respective ownership percentages in preparation of the consolidated statements of changes in equity. However, when distributions related to the incentive distribution rights are made, net income equal to the amount of those distributions is first allocated to the general partner before the remaining net income is allocated to the unitholders based on their respective ownership percentages. Basic and diluted net income per unit is the same because the Partnership does not have any potentially dilutive units outstanding for the periods presented. Three Months Ended March 31, 2024 Limited Partners' Common Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution $ 16,607 $ — $ 16,607 Distribution in excess of net income (1,774) — (1,774) Net income $ 14,833 $ — $ 14,833 Weighted average units outstanding: Basic and diluted 35,228,134 35,228,134 Net income per limited partner unit: Basic and diluted $ 0.42 Three Months Ended March 31, 2023 Limited Partners' Common Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution $ 16,603 $ — $ 16,603 Distribution in excess of net income (1,711) — (1,711) Net income $ 14,892 $ — $ 14,892 Weighted average units outstanding: Basic and diluted 35,221,868 35,221,868 Net income per limited partner unit: Basic and diluted $ 0.42
Distributions Made to Limited Partner, by Distribution	If cash distributions to the Partnership's unitholders exceed $1.2938 per common unit in any quarter, the Partnership's unitholders and Westlake, as the holder of the Partnership's incentive distribution rights, will receive distributions according to the following percentage allocations: Marginal Percentage Interest in Distributions Total Quarterly Distribution Per Unit Unitholders IDR Holders Above $1.2938 up to $1.4063 85.0 % 15.0 % Above $1.4063 up to $1.6875 75.0 % 25.0 % Above $1.6875 50.0 % 50.0 % Distributions per common unit for the three months ended March 31, 2024 and 2023 were as follows: Three Months Ended March 31, 2024 2023 Distributions per common unit $ 0.4714 $ 0.4714

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2024
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	Sales to related parties were as follows: Three Months Ended March 31, 2024 2023 Net sales—Westlake $ 235,209 $ 257,471 Charges from related parties in cost of sales were as follows: Three Months Ended March 31, 2024 2023 Feedstock purchased from Westlake and included in cost of sales $ 78,537 $ 103,042 Other charges from Westlake and included in cost of sales 32,068 30,906 Total $ 110,605 $ 133,948 Charges from related parties included within selling, general and administrative expenses were as follows: Three Months Ended March 31, 2024 2023 Services received from Westlake and included in selling, general and administrative expenses $ 6,099 $ 6,671 Charges from related parties for goods and services capitalized as assets were as follows: Three Months Ended March 31, 2024 2023 Goods and services purchased from Westlake and capitalized as assets $ 412 $ 699 The Partnership's receivable under the Investment Management Agreement was as follows: March 31, December 31, Receivable under the Investment Management Agreement $ 94,477 $ 94,444 The Partnership's accounts receivable from Westlake were as follows: March 31, December 31, Accounts receivable—Westlake $ 41,766 $ 49,565 The Partnership's accounts payable to Westlake were as follows: March 31, December 31, Accounts payable—Westlake $ 8,439 $ 15,166 Debt payable to related parties was as follows: March 31, December 31, Long-term debt payable to Westlake $ 399,674 $ 399,674

Long-term Debt Payable to Wes_2

Long-term Debt Payable to Westlake (Tables)	3 Months Ended
	Mar. 31, 2024
Related Party Transactions [Abstract]
Related Party Transactions, Long-term Debt	Long-term debt payable to Westlake consists of the following: March 31, December 31, OpCo Revolver $ 22,619 $ 22,619 MLP Revolver 377,055 377,055 Long-term debt payable to Westlake $ 399,674 $ 399,674

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Summary Of Carrying And Fair Values Of Long-Term Debt	The Partnership has financial assets and liabilities subject to fair value measures. These financial assets and liabilities include cash and cash equivalents, accounts receivable, net, accounts payable and long-term debt payable to Westlake, all of which are recorded at carrying value. The amounts reported in the consolidated balance sheets for accounts receivable, net and accounts payable approximate their fair value due to the short maturities of these instruments. The carrying and fair values of the Partnership's long-term debt at March 31, 2024 and December 31, 2023 are summarized in the table below. The fair value of long-term debt is determined based on the present value of expected future cash flows using a discounted cash flow methodology. Because the Partnership's valuation methodology used for long-term debt requires the use of significant unobservable inputs, the inputs used to measure the fair value of the Partnership's long-term debt are classified as Level 3 within the fair value hierarchy. Inputs used to estimate the fair values of the Partnership's long-term debt include the selection of an appropriate discount rate. March 31, 2024 December 31, 2023 Carrying Fair Carrying Fair Long-term debt payable to Westlake $ 399,674 $ 413,825 $ 399,674 $ 408,110

Description of Business and B_3

Description of Business and Basis of Presentation (Details) $ in Thousands	Mar. 29, 2019 USD ($) shares	Aug. 04, 2014 shares	Mar. 31, 2024 numberOfCommonCarrierPipelines production_facility
Westlake Chemical OpCo LP
Limited Partners' Capital Account [Line Items]
Number of production facilities | production_facility			3
Number of common carrier pipelines | numberOfCommonCarrierPipelines			1
Westlake Chemical OpCo LP | Affiliated Entity
Limited Partners' Capital Account [Line Items]
Limited partner interest	22.80%	10.60%
Limited partner interest, additional ownership	4.50%
Amount paid to purchase additional limited partner interest | $	$ 201,445
Westlake Chemical OpCo LP | Westlake | Majority-Owned Subsidiary, Unconsolidated
Limited Partners' Capital Account [Line Items]
Limited partner interest	77.20%
Westlake Chemical OpCo GP LLC | Limited Liability Company
Limited Partners' Capital Account [Line Items]
Limited partner interest		100%
Limited Partner
Limited Partners' Capital Account [Line Items]
Number of units sold in public offering (in shares) | shares	2,940,818	12,937,500

Accounts Receivable_Third Par_3

Accounts Receivable—Third Parties (Schedule Of Accounts Receivable) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Trade customers	$ 24,306	$ 15,622
Allowance for credit losses	(435)	(278)
Other receivables	3,357	3,357
Accounts receivable, net—third parties	$ 27,228	$ 18,701

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Inventory Disclosure [Abstract]
Finished products	$ 4,375	$ 4,147
Feedstock, additives and chemicals	485	285
Inventories	$ 4,860	$ 4,432

Property, Plant and Equipment (

Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Depreciation expense on property, plant and equipment	$ 21,537	$ 20,957

Deferred Charges and Other As_2

Deferred Charges and Other Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Deferred Charges and Other Assets
Other Assets [Line Items]
Amortization expense	$ 6,457	$ 5,679

Distributions and Net Income _3

Distributions and Net Income Per Limited Partner Unit (Basic and Diluted Income Per Limited Partner Unit) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Limited Partners' Capital Account [Line Items]
Net income	$ 14,833	$ 14,892
Distributions declared	16,607	16,603
Distribution in excess of net income	$ (1,774)	$ (1,711)
Weighted average units outsanding:
Weighted average limited partner units outstanding (basic and diluted) (in units)	35,228,134	35,221,868
IDR Holders
Limited Partners' Capital Account [Line Items]
Net income	$ 0	$ 0
Subsequent distribution to IDR holders	0	0
Distribution in excess of net income	0	0
Common units
Limited Partners' Capital Account [Line Items]
Net income	14,833	14,892
Distributions declared	16,607	16,603
Distribution in excess of net income	$ (1,774)	$ (1,711)
Weighted average units outsanding:
Weighted average limited partner units outstanding (basic and diluted) (in units)	35,228,134	35,221,868
Net income per limited partner unit:
Basic (in usd per share)	$ 0.42	$ 0.42
Diluted (in usd per share)	$ 0.42	$ 0.42
Common units | Cash Distribution
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 16,607	$ 16,603

Distributions and Net Income _4

Distributions and Net Income Per Limited Partner Unit (Distributions Declared) (Details) - $ / shares		3 Months Ended
	Apr. 30, 2024	Mar. 31, 2024
Cash Distribution | Common units
Distribution Made to Limited Partner [Line Items]
Incentive distribution rights, target distribution per unit requiring marginal percentage distribution to IDR holders (in usd per share)		$ 1.2938
Above $1.2938 up to $1.4063 | Minimum
Distribution Made to Limited Partner [Line Items]
Incentive distribution rights, target distribution per unit requiring marginal percentage distribution to IDR holders (in usd per share)		1.2938
Above $1.2938 up to $1.4063 | Maximum
Distribution Made to Limited Partner [Line Items]
Incentive distribution rights, target distribution per unit requiring marginal percentage distribution to IDR holders (in usd per share)		$ 1.4063
Above $1.2938 up to $1.4063 | Unit Holders
Distribution Made to Limited Partner [Line Items]
Marginal Percentage Interest in Distributions		85%
Above $1.2938 up to $1.4063 | IDR Holders
Distribution Made to Limited Partner [Line Items]
Marginal Percentage Interest in Distributions		15%
Above $1.4063 up to $1.6875 | Minimum
Distribution Made to Limited Partner [Line Items]
Incentive distribution rights, target distribution per unit requiring marginal percentage distribution to IDR holders (in usd per share)		$ 1.4063
Above $1.4063 up to $1.6875 | Maximum
Distribution Made to Limited Partner [Line Items]
Incentive distribution rights, target distribution per unit requiring marginal percentage distribution to IDR holders (in usd per share)		$ 1.6875
Above $1.4063 up to $1.6875 | Unit Holders
Distribution Made to Limited Partner [Line Items]
Marginal Percentage Interest in Distributions		75%
Above $1.4063 up to $1.6875 | IDR Holders
Distribution Made to Limited Partner [Line Items]
Marginal Percentage Interest in Distributions		25%
Above $1.6875 | Minimum
Distribution Made to Limited Partner [Line Items]
Incentive distribution rights, target distribution per unit requiring marginal percentage distribution to IDR holders (in usd per share)		$ 1.6875
Above $1.6875 | Unit Holders
Distribution Made to Limited Partner [Line Items]
Marginal Percentage Interest in Distributions		50%
Above $1.6875 | IDR Holders
Distribution Made to Limited Partner [Line Items]
Marginal Percentage Interest in Distributions		50%
Subsequent Event | Cash Distribution | Common units
Distribution Made to Limited Partner [Line Items]
Distribution declared per unit (in usd per unit)	$ 0.4714

Distributions and Net Income _5

Distributions and Net Income Per Limited Partner Unit (Distribution Per Common Unit) (Details) - $ / shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Distribution Per Common Unit [Abstract]
Distributions per common unit (in usd per share)	$ 0.4714	$ 0.4714

Partners' Equity (Details)

Partners' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 29, 2019	Oct. 04, 2018	Aug. 04, 2014
Class of Stock [Line Items]
Partners units, maximum aggregate offering amount, ATM		$ 50,000
Affiliated Entity
Class of Stock [Line Items]
Partners' capital account, units, sold to related party (in shares)	1,401,869
Limited Partner
Class of Stock [Line Items]
Number of units sold in public offering (in shares)	2,940,818		12,937,500
Units sold in secondary offering price per unit (in dollars per share)	$ 21.40

Related Party Transactions (Sal

Related Party Transactions (Sales to Related Parties) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Affiliated Entity
Related Party Transaction [Line Items]
Net co-products, ethylene and other sales—third parties	$ 235,209	$ 257,471

Related Party Transactions (Cos

Related Party Transactions (Cost of Sales from Related Parties) (Details) - Affiliated Entity - Westlake - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Related Party Transaction [Line Items]
Charges from related parties in cost of sales	$ 110,605	$ 133,948
Feedstock Purchased
Related Party Transaction [Line Items]
Charges from related parties in cost of sales	78,537	103,042
Other service charges
Related Party Transaction [Line Items]
Charges from related parties in cost of sales	$ 32,068	$ 30,906

Related Party Transactions (Ser

Related Party Transactions (Services from Related Parties Included in SG&A Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Related Party Transaction [Line Items]
Selling, General and Administrative Expense	$ 7,077	$ 7,914
Affiliated Entity | Westlake
Related Party Transaction [Line Items]
Selling, General and Administrative Expense	$ 6,099	$ 6,671

Related Party Transactions (Goo

Related Party Transactions (Goods and Services Purchased from Westlake and Capitalized as Assets) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Affiliated Entity | Westlake
Related Party Transaction [Line Items]
Goods and services purchased from Westlake and capitalized as assets	$ 412	$ 699

Related Party Transactions (Acc

Related Party Transactions (Accounts Receivable from and Accounts Payable to Related Parties) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2021	Dec. 31, 2023
Related Party Transaction [Line Items]
IMA, Partnership earned amount added to market rate, basis points	five
Receivable under the Investment Management Agreement—Westlake Corporation ("Westlake")	$ 94,477			$ 94,444
Shortfall			$ 58,906
Shortfall fees recovered	189
Affiliated Entity
Related Party Transaction [Line Items]
Accounts receivable, net	41,766			49,565
Accounts payable	8,439			15,166
Affiliated Entity | Westlake
Related Party Transaction [Line Items]
Interest earned related to the IMA	1,305	$ 907
Affiliated Entity | Westlake | Accounts Receivable
Related Party Transaction [Line Items]
Accrued interest included in receivable under IMA	$ 1,305			$ 1,272

Related Party Transactions (Gen

Related Party Transactions (General) (Details)	3 Months Ended
	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)
Related Party Transaction [Line Items]
Site lease agreement, number	2
Site lease agreements, term (in years)	50
Site lease agreements, OpCo annual obligation to WLK	$ 1
Affiliated Entity | Westlake
Related Party Transaction [Line Items]
Operating lease expense	$ 425,000	$ 737,000

Related Party Transactions (Deb

Related Party Transactions (Debt Payable to Related Parties) (Details) - Affiliated Entity - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Related Party Transaction [Line Items]
Accrued interest on related party debt	$ 6,617		$ 6,675
Westlake
Related Party Transaction [Line Items]
Interest expense	6,581	$ 7,315
Long-term debt payable to Westlake	399,674		399,674
Westlake | Accrued Liabilities
Related Party Transaction [Line Items]
Accrued interest on related party debt	6,617		$ 6,675
Westlake | Other income (expense)
Related Party Transaction [Line Items]
Interest expense	$ 6,581	$ 7,315

Related Party Transactions (Maj

Related Party Transactions (Major Customer and Concentration Risk) (Details)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Affiliated Entity | Westlake | Revenue Benchmark | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	82.60%	83.70%

Long-term Debt Payable to Wes_3

Long-term Debt Payable to Westlake (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Weighted average interest rate	7.20%	7.20%
Limited Partner | Senior Unsecured Revolving Credit Facility
Related Party Transaction [Line Items]
Long-term debt payable to Westlake	$ 399,674	$ 399,674
Limited Partner | Senior Unsecured Revolving Credit Facility | Long-term debt payable to Westlake
Related Party Transaction [Line Items]
Long-term debt payable to Westlake	$ 22,619	22,619
Basis spread on variable rate, percent	1.75%
Limited Partner | Senior Unsecured Revolving Credit Facility | Long-term debt payable to Westlake | SOFR
Related Party Transaction [Line Items]
Basis spread on variable rate, percent	0.10%
Limited Partner | Senior Unsecured Revolving Credit Facility | MLP Revolver
Related Party Transaction [Line Items]
Long-term debt payable to Westlake	$ 377,055	$ 377,055
Limited Partner | Senior Unsecured Revolving Credit Facility | MLP Revolver | Minimum
Related Party Transaction [Line Items]
Basis spread on variable rate, percent	1.75%
Limited Partner | Senior Unsecured Revolving Credit Facility | MLP Revolver | Maximum
Related Party Transaction [Line Items]
Basis spread on variable rate, percent	2.75%
Limited Partner | Senior Unsecured Revolving Credit Facility | MLP Revolver | SOFR
Related Party Transaction [Line Items]
Basis spread on variable rate, percent	0.10%

Fair Value Measurements (Summar

Fair Value Measurements (Summary of Carrying and Fair Values of Long Term Debt) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt payable to Westlake, fair value	$ 413,825	$ 408,110
Westlake | Affiliated Entity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt payable to Westlake	$ 399,674	$ 399,674

Supplemental Information (Detai

Supplemental Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Accrued Liabilities [Abstract]
Accrued and other liabilities	$ 19,801		$ 24,980
Accrued maintenance	2,743		5,170
Accrued capital expenditures	2,310		4,627
Accrued taxes	3,439		3,033
Capital expenditures incurred but not yet paid	5,495	$ 2,091
Interest paid	6,640	$ 4,696
Right-of-use assets	0		5,079
Affiliated Entity
Accrued Liabilities [Abstract]
Accrued interest on related party debt	$ 6,617		$ 6,675