Westlake Chemical Partners (WLKP) 10-Q 3 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Jul. 27, 2017
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Trading Symbol	WLKP
Entity Registrant Name	WESTLAKE CHEMICAL PARTNERS LP
Entity Central Index Key	1,604,665
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Common units [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		14,373,615
Subordinated units [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		12,686,115

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 104,939	$ 88,900
Accounts receivable—Westlake Chemical Corporation (Westlake)	79,367	126,977
Accounts receivable, net—third parties	14,720	12,085
Inventories	4,558	3,934
Prepaid expenses and other current assets	45	269
Total current assets	203,629	232,165
Property, plant and equipment, net	1,220,393	1,222,238
Other assets, net
Goodwill	5,814	5,814
Deferred charges and other assets, net	92,741	95,011
Total other assets, net	98,555	100,825
Total assets	1,522,577	1,555,228
Current liabilities
Accounts payable—Westlake	14,058	12,130
Accounts payable—third parties	7,102	9,930
Accrued liabilities	15,230	15,717
Total current liabilities	36,390	37,777
Long-term debt payable to Westlake	588,280	594,629
Deferred income taxes	1,936	1,736
Other liabilities	168	123
Total liabilities	626,774	634,265
Commitments and contingencies (Note 15)
EQUITY
Accumulated other comprehensive income	243	200
Total Westlake Chemical Partners LP partners' capital	102,953	102,484
Noncontrolling interest in Westlake Chemical OpCo LP (OpCo)	792,850	818,479
Total equity	895,803	920,963
Total liabilities and equity	1,522,577	1,555,228
Limited Partner [Member] | Common units [Member] | Public [Member]
EQUITY
Limited Partners' Capital Account	297,486	297,367
Total equity	297,486	297,367
Limited Partner [Member] | Common units [Member] | Westlake [Member]
EQUITY
Limited Partners' Capital Account	4,825	4,813
Total equity	4,825	4,813
Limited Partner [Member] | Subordinated units [Member] | Westlake [Member]
EQUITY
Limited Partners' Capital Account	42,649	42,534
Total equity	42,649	42,534
General Partner [Member] | Westlake [Member]
EQUITY
General partner—Westlake	(242,250)	(242,430)
Total equity	$ (242,250)	$ (242,430)

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - shares	Jun. 30, 2017	Dec. 31, 2016
Common units [Member] | Public [Member]
Units issued	12,937,500	12,937,500
Units outstanding	12,937,500	12,937,500
Common units [Member] | Westlake [Member]
Units issued	1,436,115	1,436,115
Units outstanding	1,436,115	1,436,115
Subordinated units [Member] | Westlake [Member]
Units issued	12,686,115	12,686,115
Units outstanding	12,686,115	12,686,115

Consolidated Statements of Ope

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net sales—Westlake	$ 240,989	$ 181,635	$ 453,919	$ 412,895
Net co-product, ethylene and other sales—third parties	49,124	29,206	113,642	50,550
Total net sales	290,113	210,841	567,561	463,445
Cost of sales	190,542	122,460	370,029	264,650
Gross profit	99,571	88,381	197,532	198,795
Selling, general and administrative expenses	6,886	5,848	14,714	11,945
Income from operations	92,685	82,533	182,818	186,850
Other income (expense)
Interest expense—Westlake	(5,942)	(1,203)	(11,402)	(2,434)
Other income, net	24	159	1,682	243
Income before income taxes	86,767	81,489	173,098	184,659
Provision for income taxes	297	297	600	696
Net income	86,470	81,192	172,498	183,963
Less: Net income attributable to noncontrolling interest in OpCo	76,495	71,848	152,759	162,535
Net income attributable to Westlake Chemical Partners LP	$ 9,975	$ 9,344	$ 19,739	$ 21,428
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding (basic and diluted) (in shares)	27,059,730	27,059,730	27,059,730	27,059,730
Distributions per common unit (usd per share)	$ 0.3549	$ 0.3168	$ 0.6999	$ 0.6248
Common units [Member]
Other income (expense)
Net income attributable to Westlake Chemical Partners LP	$ 5,127	$ 4,939	$ 10,191	$ 11,357
Net income per limited partner unit attributable to Westlake Chemical Partners LP (basic and diluted)
Income per limited partner unit (usd per share)	$ 0.36	$ 0.34	$ 0.71	$ 0.79
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding (basic and diluted) (in shares)	14,373,615	14,373,615	14,373,615	14,373,615
Common units [Member] | Public [Member]
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding (basic and diluted) (in shares)	12,937,500	12,937,500	12,937,500	12,937,500
Common units [Member] | Westlake [Member]
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding (basic and diluted) (in shares)	1,436,115	1,436,115	1,436,115	1,436,115
Subordinated units [Member]
Other income (expense)
Net income attributable to Westlake Chemical Partners LP	$ 4,525	$ 4,359	$ 8,994	$ 10,023
Net income per limited partner unit attributable to Westlake Chemical Partners LP (basic and diluted)
Income per limited partner unit (usd per share)	$ 0.36	$ 0.34	$ 0.71	$ 0.79
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding (basic and diluted) (in shares)	12,686,115	12,686,115	12,686,115	12,686,115
Subordinated units [Member] | Westlake [Member]
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding (basic and diluted) (in shares)	12,686,115	12,686,115	12,686,115	12,686,115

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 86,470	$ 81,192	$ 172,498	$ 183,963
Change in fair value of cash flow hedge	(51)	(267)	7	(1,094)
Reclassification of loss to net income	5	94	36	190
Total other comprehensive income (loss)	(46)	(173)	43	(904)
Comprehensive income	86,424	81,019	172,541	183,059
Comprehensive income attributable to noncontrolling interest in OpCo	76,495	71,848	152,759	162,535
Comprehensive income attributable to Westlake Chemical Partners LP	$ 9,929	$ 9,171	$ 19,782	$ 20,524

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest in OpCo [Member]	Westlake [Member]General Partner [Member]	Common units [Member]Public [Member]Limited Partner [Member]	Common units [Member]Westlake [Member]Limited Partner [Member]	Subordinated units [Member]Westlake [Member]Limited Partner [Member]
Equity, beginning balance at Dec. 31, 2015	$ 847,167	$ 280	$ 750,606	$ (242,572)	$ 294,565	$ 4,502	$ 39,786
Net income	183,963	0	162,535	48	10,222	1,135	10,023
Net effect of cash flow hedge	(904)	(904)	0	0	0	0	0
Quarterly distributions to unitholders	(16,910)	0	0	(2)	(8,083)	(898)	(7,927)
Quarterly distribution to noncontrolling interest retained in OpCo by Westlake	(149,566)	0	(149,566)	0	0	0	0
Equity, ending balance at Jun. 30, 2016	863,750	(624)	763,575	(242,526)	296,704	4,739	41,882
Equity, beginning balance at Dec. 31, 2016	920,963	200	818,479	(242,430)	297,367	4,813	42,534
Net income	172,498	0	152,759	554	9,174	1,017	8,994
Net effect of cash flow hedge	43	43	0	0	0	0	0
Quarterly distributions to unitholders	(19,313)	0	0	(374)	(9,055)	(1,005)	(8,879)
Quarterly distribution to noncontrolling interest retained in OpCo by Westlake	(178,388)	0	(178,388)	0	0	0	0
Equity, ending balance at Jun. 30, 2017	$ 895,803	$ 243	$ 792,850	$ (242,250)	$ 297,486	$ 4,825	$ 42,649

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities
Net income	$ 172,498	$ 183,963
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	57,449	41,182
Provision for doubtful accounts	475	37
(Gain)/loss from disposition of property, plant and equipment	(107)	2,467
Gain on involuntary conversion of assets	(1,672)	0
Deferred income taxes	200	320
Changes in operating assets and liabilities
Accounts receivable—third parties	(3,110)	2,270
Net accounts receivable—Westlake	49,538	(36,703)
Inventories	(624)	1,386
Prepaid expenses and other current assets	224	194
Accounts payable	(2,355)	24,833
Accrued and other liabilities	(667)	26,905
Other, net	(9,563)	(61,577)
Cash flows from investing activities	262,286	185,277
Cash flows from investing activities
Additions to property, plant and equipment	(43,996)	(168,533)
Proceeds from disposition of assets	127	98
Proceeds from involuntary conversion of assets	1,672	0
Net cash used for investing activities	(42,197)	(168,435)
Cash flows from financing activities
Proceeds from debt payable to Westlake	20,384	131,832
Repayment of debt payable to Westlake	(26,733)	(500)
Quarterly distributions to noncontrolling interest retained in OpCo by Westlake	(178,388)	(149,566)
Quarterly distributions to unitholders	(19,313)	(16,910)
Net cash used for financing activities	(204,050)	(35,144)
Net increase (decrease) in cash and cash equivalents	16,039	(18,302)
Cash and cash equivalents at beginning of period	88,900	169,559
Cash and cash equivalents at end of period	$ 104,939	$ 151,257

Description of Business and Bas

Description of Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2017
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% 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. On April 29, 2015, the Partnership purchased an additional 2.7% newly-issued limited partner interest in OpCo for approximately $135,341 , resulting in an aggregate 13.3% limited partner interest in OpCo effective April 1, 2015. OpCo owns three ethylene production facilities and a common carrier ethylene pipeline. 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 December 31, 2016 combined and 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, 2016 (the "2016 Form 10-K"), filed with the SEC on March 7, 2017. These financial statements have been prepared in conformity with the accounting principles and practices as disclosed in the notes to the combined and consolidated financial statements of the Partnership for the fiscal year ended December 31, 2016. References to "Westlake" refer collectively to Westlake Chemical Corporation and its subsidiaries, other than the Partnership, OpCo and OpCo GP. The Partnership holds a 13.3% limited partner interest and the entire non-economic general partner interest in OpCo. The remaining 86.7% limited partner interest in OpCo is owned 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 86.7% 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 June 30, 2017 , its results of operations for the three and six months ended June 30, 2017 and 2016 and the changes in its cash position for the six months ended June 30, 2017 and 2016 . 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, 2017 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. Recent Accounting Pronouncements Revenue from Contracts with Customers (ASU No. 2014-09) In May 2014, the Financial Accounting Standards Board ("FASB") issued an accounting standards update on a comprehensive new revenue recognition standard that will supersede the existing revenue recognition guidance. The new accounting guidance creates a framework by which an entity will allocate the transaction price to separate performance obligations and recognize revenue when each performance obligation is satisfied. Under the new standard, entities will be required to use judgment and make estimates, including identifying performance obligations in a contract, estimating the amount of variable consideration to include in the transaction price, allocating the transaction price to each separate performance obligation and determining when an entity satisfies its performance obligations. The standard allows for either "full retrospective" adoption, meaning that the standard is applied to all of the periods presented with a cumulative catch-up as of the earliest period presented, or "modified retrospective" adoption, meaning the standard is applied only to the most current period presented in the financial statements with a cumulative catch-up as of the current period. In 2016, the FASB issued various additional authoritative guidance for the new revenue recognition standard. The accounting standard will be effective for reporting periods beginning after December 15, 2017. The Partnership is in the process of performing a detailed analysis of its contracts with customer to evaluate the potential impact that the new accounting standard will have on its consolidated financial position, results of operations and cash flows. The Partnership intends to elect the modified retrospective method of adoption. Leases (ASU No. 2016-02) In February 2016, the FASB issued an accounting standards update on a new lease standard that will supersede the existing lease guidance. The standard requires a lessee to recognize assets and liabilities related to long-term leases that are classified as operating leases under current guidance on its balance sheet. An asset would be recognized related to the right to use the underlying asset and a liability would be recognized related to the obligation to make lease payments over the term of the lease. The standard also requires expanded disclosures related to leases. The accounting standard will be effective for reporting periods beginning after December 15, 2018. The Partnership is in the process of evaluating the impact that the new accounting guidance will have on its consolidated financial position, results of operations and cash flows. Credit Losses (ASU No. 2016-13) In June 2016, the FASB issued an accounting standards update providing new guidance for the accounting for credit losses on loans and other financial instruments. The new guidance introduces an approach based on expected losses to estimate credit losses on certain types of financial instruments. The standard also modifies the impairment model for available-for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Partnership's consolidated financial position, results of operations and cash flows. Cash Flows (ASU No. 2016-15) In August 2016, the FASB issued an accounting standards update providing new guidance on the classification of certain cash receipts and payments including debt extinguishment costs, debt prepayment costs, settlement of zero-coupon debt instruments, contingent consideration payments, proceeds from the settlement of insurance claims and life insurance policies and distributions received from equity method investees in the statement of cash flows. This update is required to be applied using the retrospective transition method to each period presented unless it is impracticable to be applied retrospectively. In such situation, this guidance is to be applied prospectively. The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have an impact on the Partnership's consolidated financial position, results of operations and cash flows. Business Combinations (ASU No. 2017-01) In January 2017, the FASB issued an accounting standards update to assist entities with evaluating when a set of transferred assets and activities is a business. The guidance requires an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets; if so, the set of transferred assets and activities is not a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs by more closely aligning it with how outputs are described in the FASB ASC Topic 606, Revenue from contracts with customers.The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have an impact on the Partnership's consolidated financial position, results of operations and cash flows. Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (ASU No. 2017-05) In February 2017, the FASB issued an accounting standards update to clarify the scope of guidance related to other income—gains and losses from the derecognition of nonfinancial assets, and to add guidance for partial sales of nonfinancial assets. The new guidance clarifies that an in substance nonfinancial asset is an asset or group of assets for which substantially all of the fair value consists of nonfinancial assets and the group or subsidiary is not a business. The guidance also outlines that when an entity transfers its controlling interest in a nonfinancial asset, but retains a noncontrolling interest, it will measure the retained interest at fair value resulting in full gain or loss recognition upon sale of the controlling interest. The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have an impact on the Partnership's consolidated financial position, results of operations and cash flows. Recently Adopted Accounting Standard Amendments to the Consolidation Analysis (ASU No. 2016-17) In October 2016, the FASB issued an accounting standards update making certain changes to the current consolidation guidance. The amendments affect reporting entities that are required to evaluate whether they should consolidate a variable interest entity in certain situations involving entities under common control. Specifically, the amendments change the evaluation of whether a reporting entity is the primary beneficiary of a variable interest entity by changing how a reporting entity that is a single decision maker of a variable interest entity treats indirect interests in the entity held through related parties that are under common control with the reporting entity. The amendments became effective for annual periods beginning after December 15, 2016. The Partnership adopted this accounting standard effective January 1, 2017, and the adoption did not have any impact on the Partnership's consolidated financial position, results of operations and cash flow.

Financial Instruments Financial

Financial Instruments Financial Instruments	6 Months Ended
	Jun. 30, 2017
Financial Instruments [Abstract]
Financial Instruments	Financial Instruments Cash Equivalents The Partnership had $9,996 of held-to-maturity securities with original maturities of three months or less, primarily consisting of corporate debt securities, classified as cash equivalents at June 30, 2017 . The Partnership's investments in held-to-maturity securities are held at amortized cost, which approximates fair value. There were no held-to-maturity securities, classified as cash equivalents, at December 31, 2016 .

Accounts Receivable - Third Par

Accounts Receivable - Third Parties	6 Months Ended
	Jun. 30, 2017
Accounts Receivable, Net [Abstract]
Accounts Receivable - Third Parties	Accounts Receivable—Third Parties Accounts receivable—third parties consist of the following: June 30, December 31, Trade customers $ 15,759 $ 11,913 Allowance for doubtful accounts (1,039 ) (564 ) 14,720 11,349 Other — 736 Accounts receivable, net—third parties $ 14,720 $ 12,085

Inventories

Inventories	6 Months Ended
	Jun. 30, 2017
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consist of the following: June 30, December 31, Finished products $ 4,223 $ 3,610 Feedstock, additives and chemicals 335 324 Inventories $ 4,558 $ 3,934

Property, Plant and Equipment

Property, Plant and Equipment	6 Months Ended
	Jun. 30, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment As of June 30, 2017 , the Partnership had property, plant and equipment, net totaling $1,220,393 . The Partnership assesses these assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable, including when negative conditions such as significant current or projected operating losses exist. Other factors considered by the Partnership when determining if an impairment assessment is necessary include, but are not limited to, significant changes or projected changes in supply and demand fundamentals (which would have a negative impact on operating rates or margins), new technological developments, new competitors with significant raw material or other cost advantages, adverse changes associated with the U.S. and world economies and uncertainties associated with governmental actions. Long-lived assets assessed for impairment are grouped at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities. Depreciation expense on property, plant and equipment of $22,251 and $17,094 is included in cost of sales in the consolidated statements of operations for the three months ended June 30, 2017 and 2016 , respectively. Depreciation expense on property, plant and equipment of $45,664 and $33,647 is included in cost of sales in the consolidated statements of operations for the six months ended June 30, 2017 and 2016, respectively.

Other Assets

Other Assets	6 Months Ended
	Jun. 30, 2017
Other Assets, Noncurrent [Abstract]
Other Assets	Other Assets Amortization expense on other assets of $5,047 and $3,692 is included in costs of sales in the consolidated statements of operations for the three months ended June 30, 2017 and 2016 , respectively. Amortization expense on other assets of $11,785 and $7,535 is included in costs of sales in the consolidated statements of operations for the six months ended June 30, 2017 and 2016 , respectively.

Distributions and Net Income Pe

Distributions and Net Income Per Limited Partner Unit	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Distributions and Net Income Per Limited Partner Unit	Distributions and Net Income Per Limited Partner Unit On August 1, 2017 , the board of directors of Westlake Chemical Partners GP LLC ("Westlake GP"), the Partnership's general partner, declared a quarterly cash distribution for the period from April 1, 2017 through June 30, 2017 of $0.3650 per unit and of $323 to the holders of the Partnership's incentive distribution rights ("IDR Holders"). This distribution is payable on August 29, 2017 to unitholders and IDR Holders of record as of August 15, 2017 . The Partnership Agreement provides that the Partnership will distribute cash each quarter during the subordination period in the following manner: first, to the holders of common units, until each common unit has received the minimum quarterly distribution of $0.2750 , plus any arrearages from prior quarters; second, to the holders of subordinated units, until each subordinated unit has received the minimum quarterly distribution of $0.2750 ; and third, to the holders of common and subordinated units, pro-rata, until each unit has received a distribution of $0.3163 . If cash distributions to the Partnership's unitholders exceed $0.3163 per common unit and subordinated 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 $0.3163 up to $0.3438 85.0 % 15.0 % Above $0.3438 up to $0.4125 75.0 % 25.0 % Above $0.4125 50.0 % 50.0 % For the three months ended June 30, 2017 , the Partnership's distribution exceeded the $0.3163 per common and subordinated unit target, which resulted in distributions to the IDR Holders. The distributions are declared subsequent to quarter end; therefore, the table below represents total distributions declared from earnings of the related periods pertaining to such distributions. Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Net income attributable to the Partnership $ 9,975 $ 9,344 $ 19,739 $ 21,428 Less: Limited partners' distribution declared on common units 5,246 4,684 10,347 9,238 Limited partners' distribution declared on subordinated units 4,631 4,134 9,133 8,153 Distribution declared with respect to the incentive distribution rights 323 46 554 48 (Distribution in excess of net income) net income in excess of distribution $ (225 ) $ 480 $ (295 ) $ 3,989 Net income per unit applicable to common limited partner units and to subordinated limited partner units is computed by dividing the respective limited partners' interest in net income by the weighted-average number of common units and subordinated 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, subordinated 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 statement of 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 June 30, 2017 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 5,246 $ 4,631 $ 323 $ 10,200 Distribution in excess of net income (119 ) (106 ) — (225 ) Net income $ 5,127 $ 4,525 $ 323 $ 9,975 Weighted average units outstanding: Basic and diluted 14,373,615 12,686,115 27,059,730 Net income per limited partner unit: Basic and diluted $ 0.36 $ 0.36 Three Months Ended June 30, 2016 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 4,684 $ 4,134 $ 46 $ 8,864 Net income in excess of distribution 255 225 — 480 Net income $ 4,939 $ 4,359 $ 46 $ 9,344 Weighted average units outstanding: Basic and diluted 14,373,615 12,686,115 27,059,730 Net income per limited partner unit: Basic and diluted $ 0.34 $ 0.34 Six Months Ended June 30, 2017 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 10,347 $ 9,133 $ 554 $ 20,034 Distribution in excess of net income (156 ) (139 ) — (295 ) Net income $ 10,191 $ 8,994 $ 554 $ 19,739 Weighted average units outstanding: Basic and diluted 14,373,615 12,686,115 27,059,730 Net income per limited partner unit: Basic and diluted $ 0.71 $ 0.71 Six Months Ended June 30, 2016 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 9,238 $ 8,153 $ 48 $ 17,439 Net income in excess of distribution 2,119 1,870 — 3,989 Net income $ 11,357 $ 10,023 $ 48 $ 21,428 Weighted average units outstanding: Basic and diluted 14,373,615 12,686,115 27,059,730 Net income per limited partner unit: Basic and diluted $ 0.79 $ 0.79

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The Partnership and OpCo regularly enter into related party transactions with Westlake. See below for a description of transactions with related parties. Sales to Related Parties OpCo sells ethylene to Westlake under the Amended Ethylene Sales Agreement. Additionally, the Partnership and OpCo from time to time provide other services or products for which each charges Westlake a fee. Sales to related parties were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Net sales—Westlake $ 240,989 $ 181,635 $ 453,919 $ 412,895 Under the Services and Secondment Agreement, OpCo uses a portion of its production capacity to process purge gas for Westlake. On August 4, 2016, OpCo and Westlake entered into an amendment to the Ethylene Sales Agreement in order to provide that certain of the pricing components that make up the price for ethylene sold thereunder would be modified to reflect the portion of OpCo's production capacity that is used to process Westlake's purge gas instead of producing ethylene and to clarify that costs specific to the processing of Westlake's purge gas would be recovered under the Services and Secondment Agreement, and not the Ethylene Sales Agreement. 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 June 30, Six Months Ended June 30, 2017 2016 2017 2016 Feedstock purchased from Westlake and included in cost of sales $ 105,877 $ 51,373 $ 202,990 $ 117,481 Other charges from Westlake and included in cost of sales 25,525 19,665 50,942 40,118 Total $ 131,402 $ 71,038 $ 253,932 $ 157,599 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 June 30, Six Months Ended June 30, 2017 2016 2017 2016 Services received from Westlake and included in selling, general and administrative expenses $ 6,946 $ 5,003 $ 13,678 $ 10,471 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 June 30, Six Months Ended June 30, 2017 2016 2017 2016 Goods and services purchased from Westlake and capitalized as assets $ 3,239 $ 11,074 $ 7,324 $ 13,081 Accounts Receivable from and Accounts Payable to Related Parties The Partnership's accounts receivable from Westlake result primarily from ethylene sales to Westlake and the shortfall recoverable from Westlake under the Ethylene Sales Agreement. Under the Ethylene Sales Agreement, if production costs billed to Westlake on an annual basis are less than 95% of the actual production costs incurred by OpCo during the year, OpCo is entitled to recover the shortfall in the subsequent year. The shortfall is recognized in the period when such production activities occur. The shortfall recognized in 2016 is recoverable during 2017, per the Ethylene Sales Agreement. During 2016, Calvert City Olefins experienced a shutdown caused by a mechanical failure, which resulted in a force majeure event under the Ethylene Sales Agreement. Based on the annual year-end measurement, a buyer deficiency fee of $13,106 was recognized as a receivable from Westlake and as a component of net sales in the consolidated financial statements as of and for the year ended December 31, 2016. The buyer deficiency fee was collected from Westlake in January 2017. 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 related party accounts receivable and accounts payable balances were as follows: June 30, December 31, Accounts receivable—Westlake $ 79,367 $ 126,977 Accounts payable—Westlake (14,058 ) (12,130 ) Debt Payable to Related Parties In connection with the IPO, OpCo assumed promissory notes payable to Westlake ("the August 2013 Promissory Notes") and entered into a senior unsecured revolving credit facility with Westlake. In April 2015, the Partnership entered into an unsecured revolving credit facility with Westlake. See Note 9 for a description of related party debt payable balances. Interest on related party debt payable balances for the three months ended June 30, 2017 and 2016 was $5,942 and $1,203 , respectively, and for the six months ended June 30, 2017 and 2016 was $11,402 and $2,434 , respectively. Interest on related party debt payable is presented as interest expense—Westlake in the consolidated statements of operations. Interest capitalized as a component of plant and equipment on related party debt was $20 and $3,050 for the three months ended June 30, 2017 and 2016 , respectively, and $418 and $5,436 for the six months ended June 30, 2017 and 2016, respectively. At June 30, 2017 and December 31, 2016 , accrued interest on related party debt was $2,967 and $5,517 , respectively, and is reflected as a component of accrued liabilities in the consolidated balance sheets. Debt payable to related parties was as follows: June 30, December 31, Long-term debt payable to Westlake $ 588,280 $ 594,629 General OpCo, together with other subsidiaries of Westlake not included in these consolidated financial statements, were guarantors under Westlake's revolving credit facility and the indentures governing its senior notes. During August 2016, OpCo and certain subsidiaries of Westlake were released from their guarantees. In 2015, the Partnership entered into an interest rate contract with Westlake to fix the London Interbank Offered Rate ("LIBOR") component of the interest rate for a portion of the MLP Revolver balance. See Note 11 for additional information on the interest rate contract. OpCo has two site lease agreements with Westlake, and each has a term of 50 years. Pursuant to the site lease agreements, OpCo pays Westlake one dollar per site per year.

Long-term Debt Payable to Westl

Long-term Debt Payable to Westlake	6 Months Ended
	Jun. 30, 2017
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: June 30, December 31, August 2013 Promissory Notes (variable interest rate of prime plus 1.5%, original scheduled maturity of August 1, 2023) $ 31,775 $ 31,775 OpCo Revolver (variable interest rate of LIBOR plus 3.0%, original scheduled maturity of August 4, 2019) 421,164 427,513 MLP Revolver (variable interest rate of LIBOR plus 2.0%, original scheduled maturity of April 29, 2018) 135,341 135,341 $ 588,280 $ 594,629 The weighted average interest rate on all long-term debt was 4.00% and 3.72% at June 30, 2017 and December 31, 2016 , respectively. As of June 30, 2017 , the Partnership was in compliance with all of the covenants under the August 2013 Promissory Notes, the OpCo Revolver and the MLP Revolver.

Accumulated Other Comprehensive

Accumulated Other Comprehensive (Loss) Income	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Accumulated Other Comprehensive (Loss) Income	Accumulated Other Comprehensive Income (Loss) Accumulated other comprehensive income or loss primarily reflects the effective portion of the gain or loss on derivative instrument designated and qualified as a cash flow hedge. Gain or loss amounts related to a cash flow hedge recorded in accumulated other comprehensive income or loss are reclassified to income in the same period in which the underlying hedged forecasted transaction affects income. If it becomes probable that a forecasted transaction will not occur, the related net gain or loss in accumulated other comprehensive income or loss is immediately reclassified into income. Changes in accumulated other comprehensive income (loss) were as follows: Six Months Ended June 30, 2017 2016 Balances at December 31, $ 200 $ 280 Interest rate contract—Other comprehensive income (loss) before reclassification 7 (1,094 ) Interest rate contract—Amounts reclassified from accumulated other comprehensive loss into net income 36 190 Balances at June 30, $ 243 $ (624 )

Derivative Instruments

Derivative Instruments	6 Months Ended
	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments The accounting guidance for derivative instruments and hedging activities requires that the Partnership recognize all derivative instruments on the balance sheet at fair value, and changes in the derivative's fair value must be currently recognized in earnings or comprehensive income, depending on the designation of the derivative. If the derivative is designated as a fair value hedge, the changes in the fair value of the derivative and of the hedged item attributable to the hedged risk are recognized in earnings. If the derivative is designated as a cash flow hedge, the effective portion of the change in the fair value of the derivative is recorded in comprehensive income and is recognized in the statement of operations when the hedged item affects earnings. Ineffective portions of changes in the fair value of cash flow hedges are recognized in earnings currently. Interest Rate Risk Management During August 2015, the Partnership entered into an interest rate contract with Westlake designed to reduce the risks of variability of the interest rate under the MLP Revolver. The interest rate contract fixed the LIBOR component of the interest rate for a portion of the MLP Revolver balance. This contract was designated as a cash flow hedge. With the exception of this interest rate contract, the Partnership did not have any other derivative financial instruments during the three and six months ended June 30, 2017 and 2016 . The fair values of the derivative instrument on the Partnership's consolidated balance sheets were as follows: Derivative Assets Derivative in Cash Flow Hedging Relationship Balance Sheet Location Fair Value as of June 30, December 31, Interest rate contract Deferred charges and other assets, net $ 299 $ 290 The following tables present the effect of the derivative instrument designated as cash flow hedge on the consolidated statements of operations and the consolidated statements of comprehensive income for the three and six months ended June 30, 2017 and 2016 : Derivative in Cash Flow Hedging Relationship Location of Loss Recognized in Statement of Operations Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Interest rate contract—Loss reclassified from accumulated other comprehensive loss Interest expense $ (5 ) $ (94 ) $ (36 ) $ (190 ) Derivative in Cash Flow Hedging Relationship Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Interest rate contract—Adjustments to fair value recognized in other comprehensive income $ 51 $ 267 $ (7 ) $ 1,094 There was no ineffective portion of the derivative instrument during the three and six months ended June 30, 2017 and 2016 . See Note 12 for the fair value of derivative instruments.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2017
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 following tables summarize, by level within the fair value hierarchy, the Partnership's liability and asset under the interest rate contract that was accounted for at fair value on a recurring basis: June 30, 2017 Level 2 Total Derivative instruments Asset—Interest rate contract $ 299 $ 299 December 31, 2016 Level 2 Total Derivative instruments Asset—Interest rate contract $ 290 $ 290 The fair value of the Level 2 interest rate contract is determined using standard valuation methodologies which incorporate relevant contract terms along with readily available market data (i.e. the 3-month LIBOR forward curve). There were no transfers in or out of Levels 1 and 2 of the fair value hierarchy during the six months ended June 30, 2017 . The Partnership has other financial assets and liabilities subject to fair value measures. These financial assets and liabilities include 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 June 30, 2017 and December 31, 2016 are summarized in the table below. The Partnership's long-term debt includes the August 2013 Promissory Notes, the OpCo Revolver and the MLP Revolver. The fair value of 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. June 30, 2017 December 31, 2016 Carrying Value Fair Value Carrying Value Fair Value August 2013 Promissory Notes $ 31,775 $ 31,775 $ 31,775 $ 31,775 OpCo Revolver 421,164 437,088 427,513 442,716 MLP Revolver 135,341 135,526 135,341 134,835

Supplemental Information

Supplemental Information	6 Months Ended
	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Information	Supplemental Information Accrued Liabilities Accrued liabilities were $15,230 and $15,717 at June 30, 2017 and December 31, 2016 , respectively. The capital expenditures accrual, accrued interest, accrued taxes, and accrued maintenance, which are components of accrued liabilities, were $2,776 , $2,967 , $3,461 , and $2,906 , respectively, at June 30, 2017 , and $2,647 , $5,517 , $1,497 , and $2,586 , respectively, at December 31, 2016 . No other component of accrued liabilities was more than five percent of total current liabilities. Non-cash Investing Activity The change in capital expenditure accrual increasing additions to property, plant and equipment was $293 for the six months ended June 30, 2017 . The change in capital expenditure accrual reducing additions to property, plant and equipment was $50,354 for the six months ended June 30, 2016 . Insurance Recovery During the six months ended June 30, 2017, the Partnership received an insurance recovery of approximately $1,672 representing involuntary conversion of assets related to the Calvert City Olefins unplanned shut-down during 2016. The insurance recovery is included in other income in the consolidated statement of operations for the six months ended June 30, 2017.

Major Customer and Concentratio

Major Customer and Concentration Risk	6 Months Ended
	Jun. 30, 2017
Risks and Uncertainties [Abstract]
Major Customer and Concentration of Credit Risk	Major Customer and Concentration of Credit Risk During the three months ended June 30, 2017 and 2016 , Westlake accounted for approximately 83.1% and 86.1% , respectively, of the Partnership's net sales. During the six months ended June 30, 2017 and 2016 , Westlake accounted for approximately 80.0% and 89.1% , respectively, of the Partnership's net sales.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2017
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 ("RCRA"), 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. Westlake will indemnify the Partnership for liabilities that occurred or existed prior to August 4, 2014. Potential Flare Modifications . For several years, the EPA has been conducting an enforcement initiative against petroleum refineries and petrochemical plants with respect to emissions from flares. On April 21, 2014, Westlake received a Clean Air Act Section 114 Information Request from the EPA which sought information regarding flares at the Calvert City and Lake Charles facilities. The EPA has informed Westlake that the information provided leads the EPA to believe that some of the flares are out of compliance with applicable standards. The EPA has indicated that it is seeking a consent decree that would obligate Westlake to take corrective actions relating to the alleged noncompliance. Westlake believes the resolution of these matters may require the payment of a monetary sanction in excess of $100 . Louisiana Notice of Violations . The Louisiana Department of Environmental Quality ("LDEQ") has issued notices of violations ("NOVs") regarding the Partnership's assets, and those of Westlake, for various air and water compliance issues. The Partnership and Westlake negotiated two settlement agreements with the LDEQ fully resolving the NOVs as well as additional violations alleged by the LDEQ though not made the subject of any specific NOV for a combined $192 in civil penalties. The penalties have been paid and upon submission of a letter withdrawing Westlake's request for administrative hearing, this matter is expected to be resolved. In addition to the matters described above, the Partnership is involved in various legal proceedings incidental to the conduct of its business. 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.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Distribution On August 1, 2017 , the board of directors of Westlake GP declared a quarterly distribution for the period from April 1, 2017 through June 30, 2017 of $0.3650 per unit and $323 to IDR Holders. This distribution is payable on August 29, 2017 to unitholders and IDR Holders of record as of August 15, 2017 . MLP Revolver Amendment On August 1, 2017, the Partnership entered into an amendment to the MLP Revolver agreement, resulting in the extension of the maturity date from April 29, 2018 to April 29, 2021. General Subsequent events were evaluated through the date on which the financial statements were issued.

Description of Business and B24

Description of Business and Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2017
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 December 31, 2016 combined and 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, 2016 (the "2016 Form 10-K"), filed with the SEC on March 7, 2017. These financial statements have been prepared in conformity with the accounting principles and practices as disclosed in the notes to the combined and consolidated financial statements of the Partnership for the fiscal year ended December 31, 2016. References to "Westlake" refer collectively to Westlake Chemical Corporation and its subsidiaries, other than the Partnership, OpCo and OpCo GP. The Partnership holds a 13.3% limited partner interest and the entire non-economic general partner interest in OpCo. The remaining 86.7% limited partner interest in OpCo is owned 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 86.7% 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 June 30, 2017 , its results of operations for the three and six months ended June 30, 2017 and 2016 and the changes in its cash position for the six months ended June 30, 2017 and 2016 . 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, 2017 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.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Revenue from Contracts with Customers (ASU No. 2014-09) In May 2014, the Financial Accounting Standards Board ("FASB") issued an accounting standards update on a comprehensive new revenue recognition standard that will supersede the existing revenue recognition guidance. The new accounting guidance creates a framework by which an entity will allocate the transaction price to separate performance obligations and recognize revenue when each performance obligation is satisfied. Under the new standard, entities will be required to use judgment and make estimates, including identifying performance obligations in a contract, estimating the amount of variable consideration to include in the transaction price, allocating the transaction price to each separate performance obligation and determining when an entity satisfies its performance obligations. The standard allows for either "full retrospective" adoption, meaning that the standard is applied to all of the periods presented with a cumulative catch-up as of the earliest period presented, or "modified retrospective" adoption, meaning the standard is applied only to the most current period presented in the financial statements with a cumulative catch-up as of the current period. In 2016, the FASB issued various additional authoritative guidance for the new revenue recognition standard. The accounting standard will be effective for reporting periods beginning after December 15, 2017. The Partnership is in the process of performing a detailed analysis of its contracts with customer to evaluate the potential impact that the new accounting standard will have on its consolidated financial position, results of operations and cash flows. The Partnership intends to elect the modified retrospective method of adoption. Leases (ASU No. 2016-02) In February 2016, the FASB issued an accounting standards update on a new lease standard that will supersede the existing lease guidance. The standard requires a lessee to recognize assets and liabilities related to long-term leases that are classified as operating leases under current guidance on its balance sheet. An asset would be recognized related to the right to use the underlying asset and a liability would be recognized related to the obligation to make lease payments over the term of the lease. The standard also requires expanded disclosures related to leases. The accounting standard will be effective for reporting periods beginning after December 15, 2018. The Partnership is in the process of evaluating the impact that the new accounting guidance will have on its consolidated financial position, results of operations and cash flows. Credit Losses (ASU No. 2016-13) In June 2016, the FASB issued an accounting standards update providing new guidance for the accounting for credit losses on loans and other financial instruments. The new guidance introduces an approach based on expected losses to estimate credit losses on certain types of financial instruments. The standard also modifies the impairment model for available-for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Partnership's consolidated financial position, results of operations and cash flows. Cash Flows (ASU No. 2016-15) In August 2016, the FASB issued an accounting standards update providing new guidance on the classification of certain cash receipts and payments including debt extinguishment costs, debt prepayment costs, settlement of zero-coupon debt instruments, contingent consideration payments, proceeds from the settlement of insurance claims and life insurance policies and distributions received from equity method investees in the statement of cash flows. This update is required to be applied using the retrospective transition method to each period presented unless it is impracticable to be applied retrospectively. In such situation, this guidance is to be applied prospectively. The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have an impact on the Partnership's consolidated financial position, results of operations and cash flows. Business Combinations (ASU No. 2017-01) In January 2017, the FASB issued an accounting standards update to assist entities with evaluating when a set of transferred assets and activities is a business. The guidance requires an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets; if so, the set of transferred assets and activities is not a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs by more closely aligning it with how outputs are described in the FASB ASC Topic 606, Revenue from contracts with customers.The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have an impact on the Partnership's consolidated financial position, results of operations and cash flows. Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (ASU No. 2017-05) In February 2017, the FASB issued an accounting standards update to clarify the scope of guidance related to other income—gains and losses from the derecognition of nonfinancial assets, and to add guidance for partial sales of nonfinancial assets. The new guidance clarifies that an in substance nonfinancial asset is an asset or group of assets for which substantially all of the fair value consists of nonfinancial assets and the group or subsidiary is not a business. The guidance also outlines that when an entity transfers its controlling interest in a nonfinancial asset, but retains a noncontrolling interest, it will measure the retained interest at fair value resulting in full gain or loss recognition upon sale of the controlling interest. The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have an impact on the Partnership's consolidated financial position, results of operations and cash flows. Recently Adopted Accounting Standard Amendments to the Consolidation Analysis (ASU No. 2016-17) In October 2016, the FASB issued an accounting standards update making certain changes to the current consolidation guidance. The amendments affect reporting entities that are required to evaluate whether they should consolidate a variable interest entity in certain situations involving entities under common control. Specifically, the amendments change the evaluation of whether a reporting entity is the primary beneficiary of a variable interest entity by changing how a reporting entity that is a single decision maker of a variable interest entity treats indirect interests in the entity held through related parties that are under common control with the reporting entity. The amendments became effective for annual periods beginning after December 15, 2016. The Partnership adopted this accounting standard effective January 1, 2017, and the adoption did not have any impact on the Partnership's consolidated financial position, results of operations and cash flow.
Derivative Instruments	Derivative Instruments The accounting guidance for derivative instruments and hedging activities requires that the Partnership recognize all derivative instruments on the balance sheet at fair value, and changes in the derivative's fair value must be currently recognized in earnings or comprehensive income, depending on the designation of the derivative. If the derivative is designated as a fair value hedge, the changes in the fair value of the derivative and of the hedged item attributable to the hedged risk are recognized in earnings. If the derivative is designated as a cash flow hedge, the effective portion of the change in the fair value of the derivative is recorded in comprehensive income and is recognized in the statement of operations when the hedged item affects earnings. Ineffective portions of changes in the fair value of cash flow hedges are recognized in earnings currently.

Accounts Receivable - Third P25

Accounts Receivable - Third Parties (Tables)	6 Months Ended
	Jun. 30, 2017
Accounts Receivable, Net [Abstract]
Schedule Of Accounts Receivable - Third Parties	Accounts receivable—third parties consist of the following: June 30, December 31, Trade customers $ 15,759 $ 11,913 Allowance for doubtful accounts (1,039 ) (564 ) 14,720 11,349 Other — 736 Accounts receivable, net—third parties $ 14,720 $ 12,085

Inventories (Tables)

Inventories (Tables)	6 Months Ended
	Jun. 30, 2017
Inventory Disclosure [Abstract]
Schedule Of Inventory	Inventories consist of the following: June 30, December 31, Finished products $ 4,223 $ 3,610 Feedstock, additives and chemicals 335 324 Inventories $ 4,558 $ 3,934

Distributions and Net Income 27

Distributions and Net Income Per Limited Partner Unit (Tables)	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Schedule of Incentive Distributions Made to Managing Members or General Partners by Distribution	If cash distributions to the Partnership's unitholders exceed $0.3163 per common unit and subordinated 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 $0.3163 up to $0.3438 85.0 % 15.0 % Above $0.3438 up to $0.4125 75.0 % 25.0 % Above $0.4125 50.0 % 50.0 % For the three months ended June 30, 2017 , the Partnership's distribution exceeded the $0.3163 per common and subordinated unit target, which resulted in distributions to the IDR Holders. The distributions are declared subsequent to quarter end; therefore, the table below represents total distributions declared from earnings of the related periods pertaining to such distributions. Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Net income attributable to the Partnership $ 9,975 $ 9,344 $ 19,739 $ 21,428 Less: Limited partners' distribution declared on common units 5,246 4,684 10,347 9,238 Limited partners' distribution declared on subordinated units 4,631 4,134 9,133 8,153 Distribution declared with respect to the incentive distribution rights 323 46 554 48 (Distribution in excess of net income) net income in excess of distribution $ (225 ) $ 480 $ (295 ) $ 3,989
Schedule of Earnings Per Share, Basic and Diluted	Net income attributable to the Partnership is allocated to the unitholders in accordance with their respective ownership percentages in preparation of the consolidated statement of 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 June 30, 2017 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 5,246 $ 4,631 $ 323 $ 10,200 Distribution in excess of net income (119 ) (106 ) — (225 ) Net income $ 5,127 $ 4,525 $ 323 $ 9,975 Weighted average units outstanding: Basic and diluted 14,373,615 12,686,115 27,059,730 Net income per limited partner unit: Basic and diluted $ 0.36 $ 0.36 Three Months Ended June 30, 2016 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 4,684 $ 4,134 $ 46 $ 8,864 Net income in excess of distribution 255 225 — 480 Net income $ 4,939 $ 4,359 $ 46 $ 9,344 Weighted average units outstanding: Basic and diluted 14,373,615 12,686,115 27,059,730 Net income per limited partner unit: Basic and diluted $ 0.34 $ 0.34 Six Months Ended June 30, 2017 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 10,347 $ 9,133 $ 554 $ 20,034 Distribution in excess of net income (156 ) (139 ) — (295 ) Net income $ 10,191 $ 8,994 $ 554 $ 19,739 Weighted average units outstanding: Basic and diluted 14,373,615 12,686,115 27,059,730 Net income per limited partner unit: Basic and diluted $ 0.71 $ 0.71 Six Months Ended June 30, 2016 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 9,238 $ 8,153 $ 48 $ 17,439 Net income in excess of distribution 2,119 1,870 — 3,989 Net income $ 11,357 $ 10,023 $ 48 $ 21,428 Weighted average units outstanding: Basic and diluted 14,373,615 12,686,115 27,059,730 Net income per limited partner unit: Basic and diluted $ 0.79 $ 0.79

Related Party Transactions (Tab

Related Party Transactions (Tables)	6 Months Ended
	Jun. 30, 2017
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	Charges from related parties for goods and services capitalized as assets were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Goods and services purchased from Westlake and capitalized as assets $ 3,239 $ 11,074 $ 7,324 $ 13,081 Debt payable to related parties was as follows: June 30, December 31, Long-term debt payable to Westlake $ 588,280 $ 594,629 Sales to related parties were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Net sales—Westlake $ 240,989 $ 181,635 $ 453,919 $ 412,895 Charges from related parties in cost of sales were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Feedstock purchased from Westlake and included in cost of sales $ 105,877 $ 51,373 $ 202,990 $ 117,481 Other charges from Westlake and included in cost of sales 25,525 19,665 50,942 40,118 Total $ 131,402 $ 71,038 $ 253,932 $ 157,599 Charges from related parties included within selling, general and administrative expenses were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Services received from Westlake and included in selling, general and administrative expenses $ 6,946 $ 5,003 $ 13,678 $ 10,471 The related party accounts receivable and accounts payable balances were as follows: June 30, December 31, Accounts receivable—Westlake $ 79,367 $ 126,977 Accounts payable—Westlake (14,058 ) (12,130 ) Long-term debt payable to Westlake consists of the following: June 30, December 31, August 2013 Promissory Notes (variable interest rate of prime plus 1.5%, original scheduled maturity of August 1, 2023) $ 31,775 $ 31,775 OpCo Revolver (variable interest rate of LIBOR plus 3.0%, original scheduled maturity of August 4, 2019) 421,164 427,513 MLP Revolver (variable interest rate of LIBOR plus 2.0%, original scheduled maturity of April 29, 2018) 135,341 135,341 $ 588,280 $ 594,629

Long-term Debt Payable to Wes29

Long-term Debt Payable to Westlake (Tables)	6 Months Ended
	Jun. 30, 2017
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	Charges from related parties for goods and services capitalized as assets were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Goods and services purchased from Westlake and capitalized as assets $ 3,239 $ 11,074 $ 7,324 $ 13,081 Debt payable to related parties was as follows: June 30, December 31, Long-term debt payable to Westlake $ 588,280 $ 594,629 Sales to related parties were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Net sales—Westlake $ 240,989 $ 181,635 $ 453,919 $ 412,895 Charges from related parties in cost of sales were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Feedstock purchased from Westlake and included in cost of sales $ 105,877 $ 51,373 $ 202,990 $ 117,481 Other charges from Westlake and included in cost of sales 25,525 19,665 50,942 40,118 Total $ 131,402 $ 71,038 $ 253,932 $ 157,599 Charges from related parties included within selling, general and administrative expenses were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Services received from Westlake and included in selling, general and administrative expenses $ 6,946 $ 5,003 $ 13,678 $ 10,471 The related party accounts receivable and accounts payable balances were as follows: June 30, December 31, Accounts receivable—Westlake $ 79,367 $ 126,977 Accounts payable—Westlake (14,058 ) (12,130 ) Long-term debt payable to Westlake consists of the following: June 30, December 31, August 2013 Promissory Notes (variable interest rate of prime plus 1.5%, original scheduled maturity of August 1, 2023) $ 31,775 $ 31,775 OpCo Revolver (variable interest rate of LIBOR plus 3.0%, original scheduled maturity of August 4, 2019) 421,164 427,513 MLP Revolver (variable interest rate of LIBOR plus 2.0%, original scheduled maturity of April 29, 2018) 135,341 135,341 $ 588,280 $ 594,629

Accumulated Other Comprehensi30

Accumulated Other Comprehensive (Loss) Income (Tables)	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Schedule of Accumulated Other Comprehensive (Loss) Income	Changes in accumulated other comprehensive income (loss) were as follows: Six Months Ended June 30, 2017 2016 Balances at December 31, $ 200 $ 280 Interest rate contract—Other comprehensive income (loss) before reclassification 7 (1,094 ) Interest rate contract—Amounts reclassified from accumulated other comprehensive loss into net income 36 190 Balances at June 30, $ 243 $ (624 )

Derivative Instruments (Tables)

Derivative Instruments (Tables)	6 Months Ended
	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Values of Derivatives Instruments in Consolidated Balance Sheet	The fair values of the derivative instrument on the Partnership's consolidated balance sheets were as follows: Derivative Assets Derivative in Cash Flow Hedging Relationship Balance Sheet Location Fair Value as of June 30, December 31, Interest rate contract Deferred charges and other assets, net $ 299 $ 290
Derivative Instruments, Gain (Loss)	The following tables present the effect of the derivative instrument designated as cash flow hedge on the consolidated statements of operations and the consolidated statements of comprehensive income for the three and six months ended June 30, 2017 and 2016 : Derivative in Cash Flow Hedging Relationship Location of Loss Recognized in Statement of Operations Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Interest rate contract—Loss reclassified from accumulated other comprehensive loss Interest expense $ (5 ) $ (94 ) $ (36 ) $ (190 ) Derivative in Cash Flow Hedging Relationship Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Interest rate contract—Adjustments to fair value recognized in other comprehensive income $ 51 $ 267 $ (7 ) $ 1,094

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value, Liabilities Measured on Recurring Basis	The following tables summarize, by level within the fair value hierarchy, the Partnership's liability and asset under the interest rate contract that was accounted for at fair value on a recurring basis: June 30, 2017 Level 2 Total Derivative instruments Asset—Interest rate contract $ 299 $ 299 December 31, 2016 Level 2 Total Derivative instruments Asset—Interest rate contract $ 290 $ 290
Summary Of Carrying And Fair Values Of Long-Term Debt	The carrying and fair values of the Partnership's long-term debt at June 30, 2017 and December 31, 2016 are summarized in the table below. The Partnership's long-term debt includes the August 2013 Promissory Notes, the OpCo Revolver and the MLP Revolver. The fair value of 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. June 30, 2017 December 31, 2016 Carrying Value Fair Value Carrying Value Fair Value August 2013 Promissory Notes $ 31,775 $ 31,775 $ 31,775 $ 31,775 OpCo Revolver 421,164 437,088 427,513 442,716 MLP Revolver 135,341 135,526 135,341 134,835

Description of Business and B33

Description of Business and Basis of Presentation (Details) $ in Thousands	Apr. 29, 2015USD ($)	Apr. 01, 2015	Aug. 04, 2014shares	Jun. 30, 2017production_facility
Westlake Chemical OpCo LP [Member] | Affiliated Entity [Member]
Limited Partners' Capital Account [Line Items]
Limited partner interest		13.30%	10.60%
Limited partner interest, additional ownership		2.70%
Amount paid to purchase additional limited partner interest | $	$ 135,341
Westlake Chemical OpCo GP LLC [Member] | Limited Liability Company [Member]
Limited Partners' Capital Account [Line Items]
Limited partner interest			100.00%
Westlake [Member] | Westlake Chemical OpCo LP [Member] | Majority-Owned Subsidiary, Unconsolidated [Member]
Limited Partners' Capital Account [Line Items]
Limited partner interest		86.70%
Westlake Chemical OpCo LP [Member]
Limited Partners' Capital Account [Line Items]
Number of ethylene production facilities | production_facility				3
Limited Partner [Member]
Limited Partners' Capital Account [Line Items]
Number of units sold in public offering | shares			12,937,500

Financial Instruments (Details)

Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Held-to-maturity Securities [Member]
Cash and Cash Equivalents [Line Items]
Cash Equivalents, at Carrying Value	$ 9,996	$ 0

Accounts Receivable - Third P35

Accounts Receivable - Third Parties Accounts Receivable—Third Parties (Schedule Of Accounts Receivable) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accounts Receivable, Net [Abstract]
Trade customers	$ 15,759	$ 11,913
Allowance for doubtful accounts	(1,039)	(564)
Trade Customer Receivable Net Current	14,720	11,349
Other	0	736
Accounts receivable, net—third parties	$ 14,720	$ 12,085

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Finished products	$ 4,223	$ 3,610
Feedstock, additives and chemicals	335	324
Inventories	$ 4,558	$ 3,934

Property, Plant and Equipment (

Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Property, plant and equipment, net	$ 1,220,393		$ 1,220,393		$ 1,222,238
Depreciation expense on property, plant and equipment	$ 22,251	$ 17,094	$ 45,664	$ 33,647

Other Assets (Details)

Other Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Other Assets [Member]
Other Assets [Line Items]
Amortization expense	$ 5,047	$ 3,692	$ 11,785	$ 7,535

Distributions and Net Income 39

Distributions and Net Income Per Limited Partner Unit (Distributions Declared) (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 01, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Distribution Made to Limited Partner [Line Items]
Net income attributable to the Partnership		$ 9,975	$ 9,344	$ 19,739	$ 21,428
Distributions declared		10,200	8,864	20,034	17,439
(Distribution in excess of net income) net income in excess of distribution		(225)	480	(295)	3,989
IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Net income attributable to the Partnership		323	46	554	48
Distribution declared with respect to the incentive distribution rights		323	46	554	48
(Distribution in excess of net income) net income in excess of distribution		0	0	0	0
Common units [Member]
Distribution Made to Limited Partner [Line Items]
Net income attributable to the Partnership		5,127	4,939	10,191	11,357
Distributions declared		5,246	4,684	10,347	9,238
(Distribution in excess of net income) net income in excess of distribution		(119)	255	(156)	2,119
Subordinated units [Member]
Distribution Made to Limited Partner [Line Items]
Net income attributable to the Partnership		4,525	4,359	8,994	10,023
Distributions declared		4,631	4,134	9,133	8,153
(Distribution in excess of net income) net income in excess of distribution		(106)	225	(139)	1,870
Cash Distribution [Member] | IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Distribution declared with respect to the incentive distribution rights		323	46	$ 554	48
Cash Distribution [Member] | IDR Holders [Member] | Subsequent Event [Member]
Distribution Made to Limited Partner [Line Items]
Distribution declared and paid to IDR holders	$ 323
Cash Distribution [Member] | Common units [Member]
Distribution Made to Limited Partner [Line Items]
Minimum quarterly distribution per unit (in usd per unit)				$ 0.2750
Distributions declared		5,246	4,684	$ 10,347	9,238
Cash Distribution [Member] | Subordinated units [Member]
Distribution Made to Limited Partner [Line Items]
Minimum quarterly distribution per unit (in usd per unit)				$ 0.2750
Distributions declared		$ 4,631	$ 4,134	$ 9,133	$ 8,153
Cash Distribution [Member] | Common And Subordinated Units [Member]
Distribution Made to Limited Partner [Line Items]
Target distribution per unit requiring marginal percentage distribution to IDR Holders (in usd per unit)				$ 0.3163
Cash Distribution [Member] | Common And Subordinated Units [Member] | Subsequent Event [Member]
Distribution Made to Limited Partner [Line Items]
Distribution declared per unit (in usd per unit)	$ 0.3650
Above $0.3163 up to $0.3438 | Minimum [Member]
Distribution Made to Limited Partner [Line Items]
Target distribution per unit requiring marginal percentage distribution to IDR Holders (in usd per unit)				0.3163
Above $0.3163 up to $0.3438 | Maximum [Member]
Distribution Made to Limited Partner [Line Items]
Target distribution per unit requiring marginal percentage distribution to IDR Holders (in usd per unit)				$ 0.3438
Above $0.3163 up to $0.3438 | IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions				15.00%
Above $0.3163 up to $0.3438 | Unit Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions				85.00%
Above $0.3438 up to $0.4125 | Minimum [Member]
Distribution Made to Limited Partner [Line Items]
Target distribution per unit requiring marginal percentage distribution to IDR Holders (in usd per unit)				$ 0.3438
Above $0.3438 up to $0.4125 | Maximum [Member]
Distribution Made to Limited Partner [Line Items]
Quarterly incentive distribution, per unit, distribution threshold				$ 0.4125
Above $0.3438 up to $0.4125 | IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions				25.00%
Above $0.3438 up to $0.4125 | Unit Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions				75.00%
Above $0.4125 | Minimum [Member]
Distribution Made to Limited Partner [Line Items]
Quarterly incentive distribution, per unit, distribution threshold				$ 0.4125
Above $0.4125 | IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions				50.00%
Above $0.4125 | Unit Holders [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions				50.00%

Distributions and Net Income 40

Distributions and Net Income Per Limited Partner Unit (Income In Excess Of Distribution) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Net income attributable to the Partnership	$ 9,975	$ 9,344	$ 19,739	$ 21,428
Distributions declared	10,200	8,864	20,034	17,439
(Distribution in excess of net income) net income in excess of distribution	(225)	480	(295)	3,989
IDR Holders [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Net income attributable to the Partnership	323	46	554	48
Distribution declared with respect to the incentive distribution rights	323	46	554	48
(Distribution in excess of net income) net income in excess of distribution	0	0	0	0
Common units [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Net income attributable to the Partnership	5,127	4,939	10,191	11,357
Distributions declared	5,246	4,684	10,347	9,238
(Distribution in excess of net income) net income in excess of distribution	(119)	255	(156)	2,119
Subordinated units [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Net income attributable to the Partnership	4,525	4,359	8,994	10,023
Distributions declared	4,631	4,134	9,133	8,153
(Distribution in excess of net income) net income in excess of distribution	(106)	225	(139)	1,870
Cash Distribution [Member] | IDR Holders [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Distribution declared with respect to the incentive distribution rights	323	46	554	48
Cash Distribution [Member] | Common units [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Distributions declared	5,246	4,684	10,347	9,238
Cash Distribution [Member] | Subordinated units [Member]
Incentive Distribution Made to Managing Member or General Partner [Line Items]
Distributions declared	$ 4,631	$ 4,134	$ 9,133	$ 8,153

Distributions and Net Income 41

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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 10,200	$ 8,864	$ 20,034	$ 17,439
(Distribution in excess of net income) net income in excess of distribution	(225)	480	(295)	3,989
Net income	$ 9,975	$ 9,344	$ 19,739	$ 21,428
Weighted average units outsanding:
Basic and diluted (shares)	27,059,730	27,059,730	27,059,730	27,059,730
Common units [Member]
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 5,246	$ 4,684	$ 10,347	$ 9,238
(Distribution in excess of net income) net income in excess of distribution	(119)	255	(156)	2,119
Net income	$ 5,127	$ 4,939	$ 10,191	$ 11,357
Weighted average units outsanding:
Basic and diluted (shares)	14,373,615	14,373,615	14,373,615	14,373,615
Net income per limited partner unit:
Income per limited partner unit (usd per share)	$ 0.36	$ 0.34	$ 0.71	$ 0.79
Subordinated units [Member]
Limited Partners' Capital Account [Line Items]
Distributions declared	$ 4,631	$ 4,134	$ 9,133	$ 8,153
(Distribution in excess of net income) net income in excess of distribution	(106)	225	(139)	1,870
Net income	$ 4,525	$ 4,359	$ 8,994	$ 10,023
Weighted average units outsanding:
Basic and diluted (shares)	12,686,115	12,686,115	12,686,115	12,686,115
Net income per limited partner unit:
Income per limited partner unit (usd per share)	$ 0.36	$ 0.34	$ 0.71	$ 0.79
IDR Holders [Member]
Limited Partners' Capital Account [Line Items]
Subsequent distribution to IDR holders	$ 323	$ 46	$ 554	$ 48
(Distribution in excess of net income) net income in excess of distribution	0	0	0	0
Net income	$ 323	$ 46	$ 554	$ 48

Related Party Transactions (Sal

Related Party Transactions (Sales to Related Parties) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Related Party Transaction [Line Items]
Net sales—Westlake	$ 240,989	$ 181,635	$ 453,919	$ 412,895
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Net sales—Westlake	$ 240,989	$ 181,635	$ 453,919	$ 412,895

Related Party Transactions (Cos

Related Party Transactions (Cost of Sales from Related Parties) (Details) - Affiliated Entity [Member] - Westlake [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Related Party Transaction [Line Items]
Charges from related parties in cost of sales	$ 131,402	$ 71,038	$ 253,932	$ 157,599
Feedstock purchased [Member]
Related Party Transaction [Line Items]
Charges from related parties in cost of sales	105,877	51,373	202,990	117,481
Other service charges [Member]
Related Party Transaction [Line Items]
Charges from related parties in cost of sales	$ 25,525	$ 19,665	$ 50,942	$ 40,118

Related Party Transactions (Ser

Related Party Transactions (Services from Related Parties Included in SG&A Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Services received from Westlake and included in selling, general and administrative expenses	$ 6,946	$ 5,003	$ 13,678	$ 10,471

Related Party Transactions (Goo

Related Party Transactions (Goods and Services from Related Parties that have been Capitalized) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Goods and services purchased from Westlake and capitalized as assets	$ 3,239	$ 11,074	$ 7,324	$ 13,081

Related Party Transactions (Acc

Related Party Transactions (Accounts Receivable from and Accounts Payable to Related Parties) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Accounts payable—Westlake	$ (14,058)	$ (12,130)
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Accounts receivable—Westlake, current and non-current	79,367	126,977
Accounts payable—Westlake	$ (14,058)	$ (12,130)

Related Party Transactions (Deb

Related Party Transactions (Debt Payable to Related Parties) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Interest on related party debt payable	$ 5,942	$ 1,203	$ 11,402	$ 2,434
Accrued interest on related party debt	2,967		2,967		$ 5,517
Long-term debt payable to Westlake	588,280		588,280		594,629
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Interest capitalized	20	3,050	418	5,436
Other income (expense) | Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Interest on related party debt payable	5,942	$ 1,203	11,402	$ 2,434
Accrued Liabilities [Member] | Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Accrued interest on related party debt	$ 2,967		$ 2,967		$ 5,517

Related Party Transactions (Gen

Related Party Transactions (General) (Details) $ in Thousands	Dec. 31, 2016USD ($)
Related Party Transaction [Line Items]
Shortfall percentage threshold	95.00%
Buyer deficiency fee	$ 13,106

Related Party Transactions (Sit

Related Party Transactions (Site Lease Agreements) (Details) - Westlake Chemical OpCo LP [Member] - Affiliated Entity [Member] - Site Lease Agreement [Member]	6 Months Ended
	Jun. 30, 2017USD ($)lease
Related Party Transaction [Line Items]
Number of site lease agreements | lease	2
Lease term	50 years
Operating lease rent expense | $	$ 1

Long-term Debt Payable to Wes50

Long-term Debt Payable to Westlake (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Long-term debt payable to Westlake	$ 588,280	$ 594,629
Weighted average interest rate	4.00%	3.72%
Limited Partner [Member] | August 2013 Promissory Note [Member] | Senior Notes [Member]
Related Party Transaction [Line Items]
Long-term debt payable to Westlake	$ 31,775	$ 31,775
Limited Partner [Member] | August 2013 Promissory Note [Member] | Senior Notes [Member] | Prime Rate [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent	1.50%	1.50%
Limited Partner [Member] | OpCo Revolver [Member] | Senior Unsecured Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Long-term debt payable to Westlake	$ 421,164	$ 427,513
Limited Partner [Member] | OpCo Revolver [Member] | Senior Unsecured Revolving Credit Facility [Member] | LIBOR [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent	3.00%	3.00%
Limited Partner [Member] | MLP Revolver [Member] | Senior Unsecured Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Long-term debt payable to Westlake	$ 135,341	$ 135,341
Limited Partner [Member] | MLP Revolver [Member] | Senior Unsecured Revolving Credit Facility [Member] | LIBOR [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent	2.00%	2.00%

Accumulated Other Comprehensi51

Accumulated Other Comprehensive (Loss) Income (Details) - Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ 200	$ 280
Interest rate contract - Other comprehensive loss before reclassification	7	(1,094)
Interest rate contract - Amounts reclassified to net income	36	190
Balance at end of period	$ 243	$ (624)

Derivative Instruments (Details

Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Derivative [Line Items]
Ineffective portion of a derivative instrument	$ 0	$ 0	$ 0
Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Change in value recognized in other comprehensive loss	51	267	(7)	$ 1,094
Interest Rate Contract [Member] | Cash Flow Hedging [Member] | Deferred charges and other assets, net [Member]
Derivative [Line Items]
Asset - Interest rate contract	299		299		$ 290
Interest Rate Contract [Member] | Interest Expense [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Loss recognized in statement of operations	$ (5)	$ (94)	$ (36)	$ (190)

Derivative Instruments (Ineffec

Derivative Instruments (Ineffective Portion) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Ineffective portion of a derivative instrument	$ 0	$ 0	$ 0

Fair Value Measurements (Summar

Fair Value Measurements (Summary of Assets and Liabilities Accounted at Fair Value on Recurring and Nonrecurring Basis) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate contract transfers between Level 1 and Level 2 fair value, amount	$ 0
Fair Value, Measurements, Recurring [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset - Interest rate contract	299	$ 290
Fair Value, Measurements, Recurring [Member] | Interest Rate Contract [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset - Interest rate contract	$ 299	$ 290

Fair Value Measurements (Summ55

Fair Value Measurements (Summary of Carrying and Fair Values of Long Term Debt) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt payable to Westlake, carrying value	$ 588,280	$ 594,629
August 2013 Promissory Note [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt payable to Westlake, fair value	31,775	31,775
August 2013 Promissory Note [Member] | Senior Notes [Member] | Limited Partner [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt payable to Westlake, carrying value	31,775	31,775
OpCo Revolver [Member] | Senior Unsecured Revolving Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt payable to Westlake, fair value	437,088	442,716
OpCo Revolver [Member] | Senior Unsecured Revolving Credit Facility [Member] | Limited Partner [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt payable to Westlake, carrying value	421,164	427,513
MLP Revolver [Member] | Senior Unsecured Revolving Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt payable to Westlake, fair value	135,526	134,835
MLP Revolver [Member] | Senior Unsecured Revolving Credit Facility [Member] | Limited Partner [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt payable to Westlake, carrying value	$ 135,341	$ 135,341

Supplemental Information (Detai

Supplemental Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Accrued Liabilities [Abstract]
Accrued liabilities	$ 15,230		$ 15,717
Accrued capital expenditures	2,776		2,647
Accrued interest	2,967		5,517
Accrued taxes	3,461		1,497
Accrued maintenance	2,906		$ 2,586
Increase (reduction) in capital expenditure accrual	293	$ (50,354)
Proceeds from involuntary conversion of assets	$ 1,672	$ 0

Major Customer and Concentrat57

Major Customer and Concentration Risk (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net sales [Member] | Customer Concentration Risk [Member] | Westlake [Member] | Affiliated Entity [Member]
Concentration Risk [Line Items]
Concentration risk percentage of net sales	83.10%	86.10%	80.00%	89.10%

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2017USD ($)settlement	Apr. 21, 2014USD ($)
Loss Contingencies [Line Items]
Number of claims settled | settlement	2
Pending Litigation [Member] | Unfavorable Regulatory Action [Member]
Loss Contingencies [Line Items]
Possible amount of claims in settlement for compliance violations		$ 100
Settled Litigation [Member]
Loss Contingencies [Line Items]
Amount of settlement for compliance violations	$ 192

Subsequent Events (Details)

Subsequent Events (Details) - Cash Distribution [Member] - Subsequent Event [Member] $ / shares in Units, $ in Thousands	Aug. 01, 2017USD ($)$ / shares
IDR Holders [Member]
Subsequent Event [Line Items]
Distribution declared and paid to IDR holders | $	$ 323
Common And Subordinated Units [Member]
Subsequent Event [Line Items]
Distribution declared per unit (in usd per unit) | $ / shares	$ 0.3650