Westlake Chemical Partners (WLKP) 10-Q 4 May 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2016	Apr. 29, 2016
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
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	Non-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	Mar. 31, 2016	Dec. 31, 2015
Current assets
Cash and cash equivalents	$ 178,676	$ 169,559
Accounts receivable—Westlake Chemical Corporation (Westlake)	56,043	39,655
Accounts receivable, net—third parties	6,066	11,927
Inventories	2,590	3,879
Prepaid expenses and other current assets	157	267
Total current assets	243,532	225,287
Property, plant and equipment, net	1,096,354	1,020,469
Other assets, net
Goodwill	5,814	5,814
Deferred charges and other assets, net	38,377	38,779
Total other assets, net	44,191	44,593
Total assets	1,384,077	1,290,349
Current liabilities
Accounts payable—Westlake	7,290	15,550
Accounts payable—third parties	29,421	18,737
Accrued liabilities	36,627	23,407
Total current liabilities	73,338	57,694
Long-term debt payable to Westlake	443,525	384,006
Deferred income taxes	1,571	1,392
Other liabilities	420	90
Total liabilities	$ 518,854	$ 443,182
Commitments and contingencies (Notes 9 and 16)
EQUITY
Accumulated other comprehensive (loss) income	$ (451)	$ 280
Total Westlake Chemical Partners LP partners' capital	99,580	96,561
Noncontrolling interest in Westlake Chemical OpCo LP (OpCo)	765,643	750,606
Total equity	865,223	847,167
Total liabilities and equity	1,384,077	1,290,349
Limited Partner [Member] | Common units [Member] | Public [Member]
EQUITY
Limited Partners' Capital Account	296,357	294,565
Total equity	296,357	294,565
Limited Partner [Member] | Common units [Member] | Westlake [Member]
EQUITY
Limited Partners' Capital Account	4,701	4,502
Total equity	4,701	4,502
Limited Partner [Member] | Subordinated units [Member] | Westlake [Member]
EQUITY
Limited Partners' Capital Account	41,543	39,786
Total equity	41,543	39,786
General Partner [Member] | Westlake [Member]
EQUITY
General Partners' Capital Account	(242,570)	(242,572)
Total equity	$ (242,570)	$ (242,572)

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - shares	Mar. 31, 2016	Dec. 31, 2015
Common units [Member] | Westlake [Member]
Units issued	1,436,115	1,436,115
Units outstanding	1,436,115	1,436,115
Common units [Member] | Public [Member]
Units issued	12,937,500	12,937,500
Units outstanding	12,937,500	12,937,500
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
	Mar. 31, 2016	Mar. 31, 2015
Net sales - Westlake	$ 231,260	$ 208,913
Net co-product, ethylene and feedstock sales—third parties	21,344	49,478
Total net sales	252,604	258,391
Cost of sales	142,190	162,164
Gross profit	110,414	96,227
Selling, general and administrative expenses	6,097	6,000
Income from operations	104,317	90,227
Other income (expense)
Interest expense—Westlake	(1,231)	(1,376)
Other income, net	84	5
Income before income taxes	103,170	88,856
Provision for income taxes	399	467
Net income	102,771	88,389
Less: Net income attributable to noncontrolling interest in OpCo	90,687	79,889
Net income attributable to Westlake Chemical Partners LP	$ 12,084	$ 8,500
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding (shares)	27,059,730	27,059,730
Common units [Member]
Other income (expense)
Net income attributable to Westlake Chemical Partners LP	$ 6,418	$ 4,516
Net income attributable to Westlake Chemical Partners LP per limited partner unit (basic and diluted)
Income per limited partner unit (usd per share)	$ 0.45	$ 0.31
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding (shares)	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 (shares)	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 (shares)	1,436,115	1,436,115
Subordinated units [Member]
Other income (expense)
Net income attributable to Westlake Chemical Partners LP	$ 5,664	$ 3,984
Net income attributable to Westlake Chemical Partners LP per limited partner unit (basic and diluted)
Income per limited partner unit (usd per share)	$ 0.45	$ 0.31
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding (shares)	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 (shares)	12,686,115	12,686,115

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 102,771	$ 88,389
Change in fair value of cash flow hedge	(827)	0
Reclassification of loss to net income	96	0
Total other comprehensive loss	(731)	0
Comprehensive income	102,040	88,389
Comprehensive income attributable to noncontrolling interest in OpCo	90,687	79,889
Comprehensive income attributable to Westlake Chemical Partners LP	$ 11,353	$ 8,500

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Noncontrolling Interest in OpCo [Member]	Accumulated Other Comprehensive Loss [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]	IDR Holders [Member]Westlake [Member]
Equity, beginning balance at Dec. 31, 2014	$ 834,950	$ 747,426	$ 0	$ (242,572)	$ 290,377	$ 4,038	$ 35,681
Net income	88,389	79,889			4,065	451	3,984
Quarterly distributions to unitholders	(7,441)				(3,558)	(395)	(3,488)
Quarterly distributions to noncontrolling interest retained in OpCo by Westlake	(85,277)	(85,277)
Equity, ending balance at Mar. 31, 2015	830,621	742,038	0	(242,572)	290,884	4,094	36,177
Equity, beginning balance at Dec. 31, 2015	847,167	750,606	280	(242,572)	294,565	4,502	39,786
Net income	102,771	90,687			5,777	641	5,664	$ 2
Net effect of cash flow hedge	(731)		(731)
Quarterly distributions to unitholders	(8,334)	0			(3,985)	(442)	(3,907)
Quarterly distributions to noncontrolling interest retained in OpCo by Westlake	(75,650)	(75,650)
Equity, ending balance at Mar. 31, 2016	$ 865,223	$ 765,643	$ (451)	$ (242,570)	$ 296,357	$ 4,701	$ 41,543

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities
Net income	$ 102,771	$ 88,389
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	20,396	19,803
Loss from disposition of property, plant and equipment	327	1
Deferred income taxes	179	54
Changes in operating assets and liabilities
Accounts receivable—third parties	5,862	20,523
Net accounts receivable—Westlake	(24,649)	(14,500)
Inventories	1,289	2,070
Prepaid expenses and other current assets	110	90
Accounts payable	7,610	589
Accrued and other liabilities	2,575	(3,477)
Other, net	(3,895)	(307)
Net cash provided by operating activities	112,575	113,235
Cash flows from investing activities
Additions to property, plant and equipment	(79,091)	(39,540)
Proceeds from disposition of assets	98	0
Net cash used for investing activities	(78,993)	(39,540)
Cash flows from financing activities
Proceeds from debt payable to Westlake	59,519	30,191
Quarterly distributions to noncontrolling interest retained in OpCo by Westlake	(75,650)	(85,277)
Quarterly distributions to unitholders	(8,334)	(7,441)
Net cash used for financing activities	(24,465)	(62,527)
Net increase in cash and cash equivalents	9,117	11,168
Cash and cash equivalents at beginning of period	169,559	133,750
Cash and cash equivalents at end of period	$ 178,676	$ 144,918

Description of Business and Bas

Description of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2016
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 facilities and related assets for the processing of natural gas liquids. 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 natural gas liquids processing 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, 2015 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, 2015 (the "2015 Form 10-K"), filed with the SEC on March 8, 2016. 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, 2015. 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. The Partnership’s operations consist exclusively of the variable interest entity’s operations and, as such, no additional variable interest entity disclosures are considered necessary. 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 March 31, 2016 , its results of operations for the three months ended March 31, 2016 and 2015 and the changes in its cash position for the three months ended March 31, 2016 and 2015 . 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, 2016 or any other 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 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 March 2016, the FASB issued additional authoritative guidance to provide clarification on principal versus agent considerations included within the new revenue recognition standard. The accounting standard (including the clarification guidance issued in March 2016) will be effective for reporting periods beginning after December 15, 2017. 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. Leases 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. Stock Compensation In March 2016, the FASB issued an accounting standards update to simplify several aspects of the accounting for share-based payment transactions, including income tax consequences, classifications of awards as either equity or liabilities and certain related classifications on the statement of cash flows. The accounting standard is effective for reporting periods beginning after December 15, 2016. 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. Recently Adopted Accounting Standards Amendments to the Consolidation Analysis In February 2015, the FASB issued an accounting standards update making certain changes to the current consolidation guidance. The amendments affect both the variable interest entity and voting interest entity consolidation models. The new standard changes the consideration of substantive rights, related party interests and fees paid to the decision maker when applying the variable interest entity consolidation model and eliminate certain guidance for limited partnerships and similar entities under the voting interest consolidation model. The accounting standard is effective for annual periods beginning after December 15, 2015. The Partnership adopted this accounting standard effective January 1, 2016 and the adoption did not have an impact on the Partnership's consolidated financial position, results of operations and cash flows. Effects on Historical Earnings per Unit of Master Limited Partnership Dropdown Transactions In April 2015, the FASB issued an accounting standard update requiring that the earnings of transferred net assets from a general partner prior to the dropdown date of the net assets to a master limited partnership be allocated entirely to the general partner when calculating earnings per unit under the two class method. As a result, previously reported earnings per unit of the limited partners will not change as a result of a dropdown transaction. The accounting standard is effective for annual periods beginning after December 15, 2015. The Partnership adopted this accounting standard effective January 1, 2016 and the adoption of this accounting standard did not have an impact on the Partnership's consolidated financial position, results of operations and cash flows. Balance Sheet Classification of Deferred Taxes In November 2015, the FASB issued an accounting standards update that requires all deferred tax assets and liabilities, along with any related valuation allowance, be classified as noncurrent on the balance sheet. As a result, each jurisdiction will now only have one net noncurrent deferred tax asset or liability. The new guidance does not change the existing requirement that only permits offsetting within a jurisdiction. The accounting standard is required to be adopted for reporting periods beginning after December 15, 2016; however, early adoption of this standard is permitted. The Partnership elected to early adopt this accounting standard, to be applied prospectively, effective January 1, 2016. Consistent with the prospective application of this accounting standard, prior period comparative information was not adjusted. The early adoption of this accounting standard did not have an impact on the Partnership's consolidated financial position, results of operations and cash flows.

Financial Instruments

Financial Instruments	3 Months Ended
	Mar. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Financial Instruments	Financial Instruments Cash Equivalents The Partnership had $115,073 and $150,031 of held-to-maturity securities with original maturities of three months or less, primarily consisting of corporate debt securities, classified as cash equivalents at March 31, 2016 and December 31, 2015 , respectively. The Partnership's investments in held-to-maturity securities are held at amortized cost, which approximates fair value.

Accounts Receivable - Third Par

Accounts Receivable - Third Parties	3 Months Ended
	Mar. 31, 2016
Accounts Receivable, Net [Abstract]
Accounts Receivable - Third Parties	Accounts Receivable—Third Parties Accounts receivable—third parties consist of the following: March 31, December 31, Trade customers $ 6,236 $ 12,097 Allowance for doubtful accounts (170 ) (170 ) Accounts receivable, net—third parties $ 6,066 $ 11,927

Inventories

Inventories	3 Months Ended
	Mar. 31, 2016
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consist of the following: March 31, December 31, Finished products $ 2,243 $ 3,527 Feedstock, additives and chemicals 347 352 Inventories $ 2,590 $ 3,879

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2016
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment As of March 31, 2016 , the Partnership had property, plant and equipment, net totaling $1,096,354 . 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 $16,553 and $15,593 is included in cost of sales in the consolidated statements of operations for the three months ended March 31, 2016 and 2015 , respectively.

Other Assets

Other Assets	3 Months Ended
	Mar. 31, 2016
Other Assets [Abstract]
Other Assets	Other Assets Amortization expense on other assets of $3,843 and $4,210 is included in the consolidated statements of operations for the three months ended March 31, 2016 and 2015 , respectively.

Distributions and Net Income Pe

Distributions and Net Income Per Limited Partner Unit	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Distributions and Net Income Per Limited Partner Unit	Distributions and Net Income Per Limited Partner Unit On April 27, 2016 , 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 January 1, 2016 through March 31, 2016 of $0.3168 per unit and of $2 to the holders of the Partnership's incentive distribution rights ("IDR Holders"). This distribution is payable on May 24, 2016 to unitholders and IDR Holders of record as of May 10, 2016 . 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 March 31, 2016, the Partnership's distribution exceeded the $0.3163 per common and subordinated unit target by $0.0005 per common and subordinated unit, which resulted in distributions to the IDR Holders. The distributions are declared subsequent to quarter end; therefore, the table below represents total cash distributions and the related periods pertaining to such distributions. Three Months Ended March 31, 2016 2015 Net income attributable to the Partnership $ 12,084 $ 8,500 Less: Limited partners' distribution declared on common units 4,554 4,065 Limited partners' distribution declared on subordinated units 4,019 3,590 Distribution declared with respect to the incentive distribution rights 2 — Net income in excess of distribution $ 3,509 $ 845 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 statements 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 March 31, 2016 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 4,554 $ 4,019 $ 2 $ 8,575 Net income in excess of distribution 1,864 1,645 — 3,509 Net income $ 6,418 $ 5,664 $ 2 $ 12,084 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 $ 0.45 $ 0.45 Three Months Ended March 31, 2015 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 4,065 $ 3,590 $ — $ 7,655 Net income in excess of distribution 451 394 — 845 Net income $ 4,516 $ 3,984 $ — $ 8,500 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 $ 0.31 $ 0.31

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2016
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 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 March 31, 2016 2015 Net sales—Westlake $ 231,260 $ 208,913 Cost of Sales from Related Parties Charges for goods and services purchased by the Partnership and OpCo from Westlake and included in cost of sales relate primarily to feedstock purchased under the Feedstock Supply Agreement and services provided under the Services and Secondment Agreement. Charges from related parties in cost of sales were as follows: Three Months Ended March 31, 2016 2015 Feedstock purchased from Westlake and included in cost of sales $ 66,108 $ 80,819 Other charges from Westlake and included in cost of sales 20,453 13,896 Total $ 86,561 $ 94,715 Services from Related Parties Included in Selling, General and Administrative Expenses Charges for services purchased by the Partnership from Westlake and included in selling, general and administrative expenses primarily relate to services Westlake performs on behalf of the Partnership under the Omnibus Agreement, including the Partnership's finance, legal, information technology, human resources, communication, ethics and compliance, and other administrative functions. Charges from related parties included within selling, general and administrative expenses were as follows: Three Months Ended March 31, 2016 2015 Services received from Westlake and included in selling, general and administrative expenses $ 5,468 $ 5,148 Goods and Services from Related Parties Capitalized as Assets Charges for goods and services purchased by the Partnership and OpCo from Westlake which were capitalized as assets relate primarily to the services of Westlake employees under the Services and Secondment Agreement. Charges from related parties for goods and services capitalized as assets were as follows: Three Months Ended March 31, 2016 2015 Goods and services purchased from Westlake and capitalized as assets $ 2,007 $ 962 Accounts Receivable from and Accounts Payable to Related Parties The Partnership's accounts receivable from Westlake result primarily from ethylene sales to Westlake under the Ethylene Sales Agreement. 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: March 31, December 31, Accounts receivable—Westlake $ 56,043 $ 39,655 Accounts payable—Westlake (7,290 ) (15,550 ) Debt Payable to Related Parties OpCo assumed promissory notes payable to Westlake ("the August 2013 Promissory Notes") and entered into a senior unsecured revolving credit facility with Westlake in connection with the IPO. The Partnership entered into an unsecured revolving credit facility with Westlake during April 2015. See Note 9 for a description of related party debt payable balances. Interest on related party debt payable balances for the three months ended March 31, 2016 and 2015 were $1,231 and $1,376 , respectively, and is presented as interest expense—Westlake in the consolidated statements of operations. Interest capitalized as a component of property, plant and equipment on related party debt was $2,386 and $1,215 for the three months ended March 31, 2016 and 2015 , respectively. At March 31, 2016 and December 31, 2015 , accrued interest on related party debt was $3,600 and $2,879 , respectively, and is reflected as a component of accrued liabilities in the consolidated balance sheets. Debt payable to related parties was as follows: March 31, December 31, Long-term debt payable to Westlake $ 443,525 $ 384,006 General OpCo, together with other subsidiaries of Westlake not included in these consolidated financial statements, are guarantors under Westlake's revolving credit facility and the indentures governing its senior notes. As of March 31, 2016 and December 31, 2015 , Westlake had outstanding letters of credit totaling $30,445 and $30,098 , respectively, under its revolving credit facility and $754,000 principal amount outstanding under its senior notes (less the unamortized discount and debt issuance costs of $6,589 and $6,741 , as of March 31, 2016 and December 31, 2015 , respectively). The indentures governing Westlake's senior notes prevent OpCo from making distributions to the Partnership if any default or event of default (as defined in the indentures) exists. However, Westlake's credit facility does not prevent OpCo from making distributions to the Partnership. In 2015, the Partnership entered into an interest rate contract with Westlake to fix the 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	3 Months Ended
	Mar. 31, 2016
Related Party Transactions [Abstract]
Long-term Debt Payable to Westlake	Long-term Debt Payable to Westlake Long-term debt payable to Westlake consists of the following: March 31, December 31, 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 London Interbank Offered Rate ("LIBOR") plus 3.0%, original scheduled maturity of August 4, 2019) 276,409 216,890 MLP Revolver (variable interest rate of LIBOR plus 2.0%, original scheduled maturity of April 29, 2018) 135,341 135,341 $ 443,525 $ 384,006 The weighted average interest rate on all long-term debt was 3.41% and 3.30% at March 31, 2016 and December 31, 2015 , respectively. As of March 31, 2016 , 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	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Accumulated Other Comprehensive (Loss) Income	Accumulated Other Comprehensive (Loss) Income 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. The following sets forth the changes in accumulated other comprehensive loss for the three months ended March 31, 2016 : Three Months Ended March 31, 2016 Balances at December 31, 2015 $ 280 Interest rate contract—Other comprehensive loss before reclassification (827 ) Interest rate contract—Amounts reclassified from accumulated other comprehensive loss into net income 96 Balances at March 31, 2016 $ (451 )

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2016
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 months ended March 31, 2016 . The Partnership did not have any interest rate contracts for the three months ended March 31, 2015 . 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 March 31, December 31, Interest rate contract Deferred charges and other assets, net $ — $ 436 Derivative Liabilities Derivative in Cash Flow Hedging Relationship Balance Sheet Location Fair Value as of March 31, December 31, Interest rate contract Other liabilities $ 312 $ — The following tables present the effect of the derivative instrument designated as cash flow hedge on the consolidated statement of operations and the consolidated statement of comprehensive income for the three months ended March 31, 2016 : Derivative in Cash Flow Hedging Relationship Location of Gain (Loss) Three Months Ended March 31, 2016 Interest rate contract—Loss reclassified from accumulated other comprehensive loss Interest expense $ (96 ) Derivative in cash flow hedge relationship Three Months Ended March 31, 2016 Interest rate contract—Change in value recognized in other comprehensive loss $ 827 There was no ineffective portion of the derivative instrument during the three months ended March 31, 2016 . See Note 12 for the fair value of derivative instruments.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2016
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: March 31, 2016 Level 2 Total Derivative instruments Liability—Interest rate contract $ 312 $ 312 December 31, 2015 Level 2 Total Derivative instruments Asset—Interest rate contract $ 436 $ 436 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 three months ended March 31, 2016. 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 March 31, 2016 and December 31, 2015 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. March 31, 2016 December 31, 2015 Carrying Value Fair Value Carrying Value Fair Value August 2013 Promissory Notes $ 31,775 $ 31,775 $ 31,775 $ 31,775 OpCo Revolver 276,409 273,324 216,890 215,738 MLP Revolver 135,341 130,814 135,341 130,439

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Partnership is a limited partnership and is treated as a partnership for U.S. federal income tax purposes and, therefore, is not liable for entity-level federal income taxes. The Partnership is, however, subject to state and local income taxes. The effective income tax rates were 0.4% and 0.5% for the three months ended March 31, 2016 and 2015 , respectively.

Supplemental Information

Supplemental Information	3 Months Ended
	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Information	Supplemental Information Accrued Liabilities Accrued liabilities were $36,627 and $23,407 at March 31, 2016 and December 31, 2015 , respectively. The accrual related to capital expenditures, which is a component of accrued liabilities, was $27,004 and $14,745 at March 31, 2016 and December 31, 2015 , respectively. 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 reducing additions to property, plant and equipment was $13,719 for the three months ended March 31, 2016 . The change in capital expenditure accrual reducing additions to property, plant and equipment was $545 for the three months ended March 31, 2015 .

Major Customer and Concentratio

Major Customer and Concentration Risk	3 Months Ended
	Mar. 31, 2016
Risks and Uncertainties [Abstract]
Major Customer and Concentration of Credit Risk	Major Customer and Concentration of Credit Risk During the three months ended March 31, 2016 and 2015 , Westlake accounted for approximately 91.6% and 80.9% , respectively, of the Partnership's net sales.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2016
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. Contract Disputes with Goodrich and PolyOne . In connection with the 1990 and 1997 acquisitions of the Goodrich Corporation ("Goodrich") chemical manufacturing facility in Calvert City, Kentucky, which is a portion of the B.F. Goodrich superfund site, Goodrich agreed to indemnify Westlake for any liabilities related to preexisting contamination at the site. Westlake agreed to indemnify Goodrich for post-closing contamination caused by Westlake's operations. The soil and groundwater at the site had been extensively contaminated under Goodrich's operations. In 1993, Goodrich spun off the predecessor of PolyOne Corporation ("PolyOne"), and that predecessor assumed Goodrich's indemnification obligations relating to preexisting contamination. In 2003, litigation arose among Westlake, Goodrich and PolyOne with respect to the allocation of the cost of remediating contamination at the site. The parties settled this litigation in December 2007, and the case was dismissed. In the settlement the parties agreed that, among other things: (1) PolyOne would pay 100% of the costs (with specified exceptions), net of recoveries or credits from third parties, incurred with respect to environmental issues at the Calvert City site from August 1, 2007 forward; (2) either Westlake or PolyOne might, from time to time in the future (but not more than once every five years), institute an arbitration proceeding to adjust that percentage; and (3) Westlake and PolyOne would negotiate a new environmental remediation utilities and Services and Secondment Agreement to cover Westlake's provision to or on behalf of PolyOne of certain environmental remediation services at the site. The current environmental remediation activities at the Calvert City site do not have a specified termination date but are expected to last for the foreseeable future. The costs incurred by Westlake that have been invoiced to PolyOne to provide the environmental remediation services were $2,210 in 2015 . By letter dated March 16, 2010, PolyOne notified Westlake that it was initiating an arbitration proceeding under the settlement agreement. In this proceeding, PolyOne sought to readjust the percentage allocation of costs and to recover approximately $1,400 from Westlake in reimbursement of previously paid remediation costs. In December 2015, the arbitration panel dismissed the proceeding with prejudice. In a separate proceeding in Ohio state court, Westlake is seeking certain insurance documents from PolyOne. Westlake will indemnify the Partnership for liabilities that occurred or existed prior to August 4, 2014. State Administrative Proceedings . There are several administrative proceedings in Kentucky involving Westlake, Goodrich and PolyOne related to the same manufacturing site in Calvert City, which includes OpCo's natural gas liquids processing facility in Calvert City. In 2003, the Kentucky Environmental and Public Protection Cabinet (the "Cabinet") re-issued Goodrich's RCRA permit which requires Goodrich to remediate contamination at the Calvert City manufacturing site. Both Goodrich and PolyOne challenged various terms of the permit in an attempt to shift Goodrich's clean-up obligations under the permit to Westlake. Westlake intervened in the proceedings. The Cabinet has suspended all corrective action under the RCRA permit in deference to a remedial investigation and feasibility study ("RIFS") being conducted, under the auspices of the U.S. Environmental Protection Agency ("EPA") pursuant to an Administrative Settlement Agreement ("AOC"), which became effective on December 9, 2009. See "Federal Administrative Proceedings" below. Periodic status conferences will be held to evaluate whether additional proceedings will be required. Federal Administrative Proceedings . In May 2009, the Cabinet sent a letter to the EPA requesting the EPA's assistance in addressing contamination at the Calvert City site under CERCLA. In its response to the Cabinet, the EPA stated that it concurred with the Cabinet's request and would incorporate work previously conducted under the Cabinet's RCRA authority into the EPA's cleanup efforts under CERCLA. Since 1983, the EPA has been addressing contamination at an abandoned landfill adjacent to the Partnership's plant which had been operated by Goodrich and which was being remediated pursuant to CERCLA. The EPA has directed Goodrich and PolyOne to conduct additional investigation activities at the landfill and at the Calvert City site. In June 2009, the EPA notified Westlake that Westlake may have potential liability under section 107(a) of CERCLA at its plant site. Liability under section 107(a) of CERCLA is strict and joint and several. The EPA also identified Goodrich and PolyOne, among others, as potentially responsible parties at the plant site. Westlake negotiated, in conjunction with the other potentially responsible parties, an AOC and an order to conduct an RIFS. Due to the Partnership's ownership and current operation of the property, the Partnership may be subject to additional requirements and liabilities under CERCLA. 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. A number of companies have entered into consent agreements with the EPA requiring both modifications to reduce flare emissions and the installation of additional equipment to better track flare operations and emissions. 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. Westlake submitted information pursuant to such request, including information regarding three flares that the Partnership owns. 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 demanded that Westlake conduct additional flare sampling and provide supplemental information. Westlake is currently in negotiations with the EPA regarding these demands, some of which are applicable to the Partnership's flares. The EPA has indicated that it is seeking a consent decree with that would obligate Westlake to take corrective actions relating to the alleged noncompliance. Westlake has not agreed that any flares are out of compliance or that any corrective actions are warranted. Depending on the outcome of Westlake's negotiations with the EPA, additional controls on emissions from the Partnership's flares may be required and these could result in increased capital and operating costs. 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 compliance issues. The Partnership and Westlake are working with LDEQ to settle these claims, and a global settlement of all claims is being discussed. While settlement may result in a total civil penalty in excess of $100 , such a settlement will likely cover assets owned by the Partnership and Westlake, and to the extent it covers the Partnership's assets, Westlake will indemnify the Partnership for liabilities that occurred or existed prior to August 4, 2014. Westlake has reached a verbal agreement with the LDEQ to settle various NOVs in two separate settlements for a combined $192 in civil penalties. 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	3 Months Ended
	Mar. 31, 2016
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 27, 2016 , the board of directors of Westlake GP declared a quarterly distribution for the period from January 1, 2016 through March 31, 2016 of $0.3168 per unit and $2 to IDR Holders. This distribution is payable on May 24, 2016 to unitholders and IDR Holders of record as of May 10, 2016 . Subsequent events were evaluated through the date on which the financial statements were issued.

Description of Business and B25

Description of Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2016
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, 2015 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, 2015 (the "2015 Form 10-K"), filed with the SEC on March 8, 2016. 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, 2015. 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. The Partnership’s operations consist exclusively of the variable interest entity’s operations and, as such, no additional variable interest entity disclosures are considered necessary. 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 March 31, 2016 , its results of operations for the three months ended March 31, 2016 and 2015 and the changes in its cash position for the three months ended March 31, 2016 and 2015 . 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, 2016 or any other 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.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements Revenue from Contracts with Customers 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 March 2016, the FASB issued additional authoritative guidance to provide clarification on principal versus agent considerations included within the new revenue recognition standard. The accounting standard (including the clarification guidance issued in March 2016) will be effective for reporting periods beginning after December 15, 2017. 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. Leases 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. Stock Compensation In March 2016, the FASB issued an accounting standards update to simplify several aspects of the accounting for share-based payment transactions, including income tax consequences, classifications of awards as either equity or liabilities and certain related classifications on the statement of cash flows. The accounting standard is effective for reporting periods beginning after December 15, 2016. 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. Recently Adopted Accounting Standards Amendments to the Consolidation Analysis In February 2015, the FASB issued an accounting standards update making certain changes to the current consolidation guidance. The amendments affect both the variable interest entity and voting interest entity consolidation models. The new standard changes the consideration of substantive rights, related party interests and fees paid to the decision maker when applying the variable interest entity consolidation model and eliminate certain guidance for limited partnerships and similar entities under the voting interest consolidation model. The accounting standard is effective for annual periods beginning after December 15, 2015. The Partnership adopted this accounting standard effective January 1, 2016 and the adoption did not have an impact on the Partnership's consolidated financial position, results of operations and cash flows. Effects on Historical Earnings per Unit of Master Limited Partnership Dropdown Transactions In April 2015, the FASB issued an accounting standard update requiring that the earnings of transferred net assets from a general partner prior to the dropdown date of the net assets to a master limited partnership be allocated entirely to the general partner when calculating earnings per unit under the two class method. As a result, previously reported earnings per unit of the limited partners will not change as a result of a dropdown transaction. The accounting standard is effective for annual periods beginning after December 15, 2015. The Partnership adopted this accounting standard effective January 1, 2016 and the adoption of this accounting standard did not have an impact on the Partnership's consolidated financial position, results of operations and cash flows. Balance Sheet Classification of Deferred Taxes In November 2015, the FASB issued an accounting standards update that requires all deferred tax assets and liabilities, along with any related valuation allowance, be classified as noncurrent on the balance sheet. As a result, each jurisdiction will now only have one net noncurrent deferred tax asset or liability. The new guidance does not change the existing requirement that only permits offsetting within a jurisdiction. The accounting standard is required to be adopted for reporting periods beginning after December 15, 2016; however, early adoption of this standard is permitted. The Partnership elected to early adopt this accounting standard, to be applied prospectively, effective January 1, 2016. Consistent with the prospective application of this accounting standard, prior period comparative information was not adjusted. The early adoption of this accounting standard did not have an impact on the Partnership's consolidated financial position, results of operations and cash flows.
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 P26

Accounts Receivable - Third Parties (Tables)	3 Months Ended
	Mar. 31, 2016
Accounts Receivable, Net [Abstract]
Schedule Of Accounts Receivable - Third Parties	Accounts receivable—third parties consist of the following: March 31, December 31, Trade customers $ 6,236 $ 12,097 Allowance for doubtful accounts (170 ) (170 ) Accounts receivable, net—third parties $ 6,066 $ 11,927

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2016
Inventory Disclosure [Abstract]
Schedule Of Inventory	Inventories consist of the following: March 31, December 31, Finished products $ 2,243 $ 3,527 Feedstock, additives and chemicals 347 352 Inventories $ 2,590 $ 3,879

Distributions and Net Income 28

Distributions and Net Income Per Limited Partner Unit (Tables)	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Schedule of Incentive Distributions Made to Managing Members or General Partners by Distribution [Table Text Block]	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 March 31, 2016, the Partnership's distribution exceeded the $0.3163 per common and subordinated unit target by $0.0005 per common and subordinated unit, which resulted in distributions to the IDR Holders. The distributions are declared subsequent to quarter end; therefore, the table below represents total cash distributions and the related periods pertaining to such distributions. Three Months Ended March 31, 2016 2015 Net income attributable to the Partnership $ 12,084 $ 8,500 Less: Limited partners' distribution declared on common units 4,554 4,065 Limited partners' distribution declared on subordinated units 4,019 3,590 Distribution declared with respect to the incentive distribution rights 2 — Net income in excess of distribution $ 3,509 $ 845
Schedule of Earnings Per Share, Basic and Diluted	when distributions related to the incentive distribution rights are made, net income equal to the amount of those distributions is first allocated to the general partner before the remaining net income is allocated to the unitholders based on their respective ownership percentages. Basic and diluted net income per unit is the same because the Partnership does not have any potentially dilutive units outstanding for the periods presented. Three Months Ended March 31, 2016 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 4,554 $ 4,019 $ 2 $ 8,575 Net income in excess of distribution 1,864 1,645 — 3,509 Net income $ 6,418 $ 5,664 $ 2 $ 12,084 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 $ 0.45 $ 0.45 Three Months Ended March 31, 2015 Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to the Partnership: Distribution declared $ 4,065 $ 3,590 $ — $ 7,655 Net income in excess of distribution 451 394 — 845 Net income $ 4,516 $ 3,984 $ — $ 8,500 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 $ 0.31 $ 0.31

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2016
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	Charges from related parties included within selling, general and administrative expenses were as follows: Three Months Ended March 31, 2016 2015 Services received from Westlake and included in selling, general and administrative expenses $ 5,468 $ 5,148 The related party accounts receivable and accounts payable balances were as follows: March 31, December 31, Accounts receivable—Westlake $ 56,043 $ 39,655 Accounts payable—Westlake (7,290 ) (15,550 ) Sales to related parties were as follows: Three Months Ended March 31, 2016 2015 Net sales—Westlake $ 231,260 $ 208,913 Charges from related parties for goods and services capitalized as assets were as follows: Three Months Ended March 31, 2016 2015 Goods and services purchased from Westlake and capitalized as assets $ 2,007 $ 962 Charges from related parties in cost of sales were as follows: Three Months Ended March 31, 2016 2015 Feedstock purchased from Westlake and included in cost of sales $ 66,108 $ 80,819 Other charges from Westlake and included in cost of sales 20,453 13,896 Total $ 86,561 $ 94,715 Debt payable to related parties was as follows: March 31, December 31, Long-term debt payable to Westlake $ 443,525 $ 384,006 Long-term debt payable to Westlake consists of the following: March 31, 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 London Interbank Offered Rate ("LIBOR") plus 3.0%, original scheduled maturity of August 4, 2019) 276,409 216,890 MLP Revolver (variable interest rate of LIBOR plus 2.0%, original scheduled maturity of April 29, 2018) 135,341 135,341 $ 443,525 $ 384,006

Long-term Debt Payable to Wes30

Long-term Debt Payable to Westlake (Tables)	3 Months Ended
	Mar. 31, 2016
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	Charges from related parties included within selling, general and administrative expenses were as follows: Three Months Ended March 31, 2016 2015 Services received from Westlake and included in selling, general and administrative expenses $ 5,468 $ 5,148 The related party accounts receivable and accounts payable balances were as follows: March 31, December 31, Accounts receivable—Westlake $ 56,043 $ 39,655 Accounts payable—Westlake (7,290 ) (15,550 ) Sales to related parties were as follows: Three Months Ended March 31, 2016 2015 Net sales—Westlake $ 231,260 $ 208,913 Charges from related parties for goods and services capitalized as assets were as follows: Three Months Ended March 31, 2016 2015 Goods and services purchased from Westlake and capitalized as assets $ 2,007 $ 962 Charges from related parties in cost of sales were as follows: Three Months Ended March 31, 2016 2015 Feedstock purchased from Westlake and included in cost of sales $ 66,108 $ 80,819 Other charges from Westlake and included in cost of sales 20,453 13,896 Total $ 86,561 $ 94,715 Debt payable to related parties was as follows: March 31, December 31, Long-term debt payable to Westlake $ 443,525 $ 384,006 Long-term debt payable to Westlake consists of the following: March 31, 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 London Interbank Offered Rate ("LIBOR") plus 3.0%, original scheduled maturity of August 4, 2019) 276,409 216,890 MLP Revolver (variable interest rate of LIBOR plus 2.0%, original scheduled maturity of April 29, 2018) 135,341 135,341 $ 443,525 $ 384,006

Accumulated Other Comprehensi31

Accumulated Other Comprehensive (Loss) Income (Tables)	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Loss	The following sets forth the changes in accumulated other comprehensive loss for the three months ended March 31, 2016 : Three Months Ended March 31, 2016 Balances at December 31, 2015 $ 280 Interest rate contract—Other comprehensive loss before reclassification (827 ) Interest rate contract—Amounts reclassified from accumulated other comprehensive loss into net income 96 Balances at March 31, 2016 $ (451 )

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2016
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 March 31, December 31, Interest rate contract Deferred charges and other assets, net $ — $ 436 Derivative Liabilities Derivative in Cash Flow Hedging Relationship Balance Sheet Location Fair Value as of March 31, December 31, Interest rate contract Other liabilities $ 312 $ —
Derivative Instruments, Gain (Loss)	The following tables present the effect of the derivative instrument designated as cash flow hedge on the consolidated statement of operations and the consolidated statement of comprehensive income for the three months ended March 31, 2016 : Derivative in Cash Flow Hedging Relationship Location of Gain (Loss) Three Months Ended March 31, 2016 Interest rate contract—Loss reclassified from accumulated other comprehensive loss Interest expense $ (96 ) Derivative in cash flow hedge relationship Three Months Ended March 31, 2016 Interest rate contract—Change in value recognized in other comprehensive loss $ 827

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2016
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: March 31, 2016 Level 2 Total Derivative instruments Liability—Interest rate contract $ 312 $ 312 December 31, 2015 Level 2 Total Derivative instruments Asset—Interest rate contract $ 436 $ 436
Summary Of Carrying And Fair Values Of Long-Term Debt	The carrying and fair values of the Partnership's long-term debt at March 31, 2016 and December 31, 2015 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. March 31, 2016 December 31, 2015 Carrying Value Fair Value Carrying Value Fair Value August 2013 Promissory Notes $ 31,775 $ 31,775 $ 31,775 $ 31,775 OpCo Revolver 276,409 273,324 216,890 215,738 MLP Revolver 135,341 130,814 135,341 130,439

Description of Business and B34

Description of Business and Basis of Presentation (Details) $ in Thousands	Apr. 29, 2015USD ($)	Apr. 01, 2015	Aug. 04, 2014shares	Mar. 31, 2016production_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	Mar. 31, 2016	Dec. 31, 2015
Held-to-maturity Securities [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 115,073	$ 150,031

Accounts Receivable - Third P36

Accounts Receivable - Third Parties Accounts Receivable—Third Parties (Schedule Of Accounts Receivable) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Accounts Receivable, Net [Abstract]
Trade customers	$ 6,236	$ 12,097
Allowance for doubtful accounts	(170)	(170)
Accounts receivable, net - third parties	$ 6,066	$ 11,927

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Finished products	$ 2,243	$ 3,527
Feedstock, additives and chemicals	347	352
Inventories	$ 2,590	$ 3,879

Property, Plant and Equipment (

Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property, plant and equipment, net	$ 1,096,354		$ 1,020,469
Depreciation expense on property, plant and equipment	$ 16,553	$ 15,593

Other Assets (Detail)

Other Assets (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Other Assets [Member]
Entity Information [Line Items]
Amortization expense	$ 3,843	$ 4,210

Distributions and Net Income 40

Distributions and Net Income Per Limited Partner Unit (Distributions Declared) (Details) - USD ($) $ / shares in Units, $ in Thousands	Apr. 27, 2016	Mar. 31, 2016	Mar. 31, 2015
IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Distribution declared to IDR holders		$ 2	$ 0
Cash Distribution [Member] | IDR Holders [Member]
Distribution Made to Limited Partner [Line Items]
Distribution declared to IDR holders		$ 2	$ 0
Cash Distribution [Member] | IDR Holders [Member] | Subsequent Event [Member]
Distribution Made to Limited Partner [Line Items]
Distribution declared to IDR holders	$ 2
Cash Distribution [Member] | Common units [Member]
Distribution Made to Limited Partner [Line Items]
Minimum quarterly distribution per unit		$ 0.2750
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		0.3163
Excess of targeted distribution per unit		0.0005
Cash Distribution [Member] | Common And Subordinated Units [Member] | Subsequent Event [Member]
Distribution Made to Limited Partner [Line Items]
Distribution declared per unit	$ 0.3168
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		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		$ 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		$ 0.3438
Above $0.3438 up to $0.4125 | Maximum [Member]
Distribution Made to Limited Partner [Line Items]
Incentive Distribution, Quarterly 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]
Incentive Distribution, Quarterly 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 41

Distributions and Net Income Per Limited Partner Unit (Income In Excess Of Distribution) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net income attributable to the Partnership	$ 12,084	$ 8,500
Limited partner's distribution declared	8,575	7,655
Net income in excess of distribution	3,509	845
Common units [Member]
Net income attributable to the Partnership	6,418	4,516
Limited partner's distribution declared	4,554	4,065
Net income in excess of distribution	1,864	451
Subordinated units [Member]
Net income attributable to the Partnership	5,664	3,984
Limited partner's distribution declared	4,019	3,590
Net income in excess of distribution	1,645	394
IDR Holders [Member]
Net income attributable to the Partnership	2	0
Distribution declared to IDR holders	2	0
Net income in excess of distribution	0	0
Cash Distribution [Member] | Common units [Member]
Limited partner's distribution declared	4,554	4,065
Cash Distribution [Member] | Subordinated units [Member]
Limited partner's distribution declared	4,019	3,590
Cash Distribution [Member] | IDR Holders [Member]
Distribution declared to IDR holders	$ 2	$ 0

Distributions and Net Income 42

Distributions and Net Income Per Limited Partner Unit (Basic and Diluted Income Per Limited Partner Unit) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Limited Partners' Capital Account [Line Items]
Limited partner's distribution declared	$ 8,575	$ 7,655
Net income in excess of distribution	3,509	845
Net income	$ 12,084	$ 8,500
Weighted average units outsanding:
Basic and diluted (shares)	27,059,730	27,059,730
Common units [Member]
Limited Partners' Capital Account [Line Items]
Limited partner's distribution declared	$ 4,554	$ 4,065
Net income in excess of distribution	1,864	451
Net income	$ 6,418	$ 4,516
Weighted average units outsanding:
Basic and diluted (shares)	14,373,615	14,373,615
Net income per limited partner unit:
Income per limited partner unit (usd per share)	$ 0.45	$ 0.31
Subordinated units [Member]
Limited Partners' Capital Account [Line Items]
Limited partner's distribution declared	$ 4,019	$ 3,590
Net income in excess of distribution	1,645	394
Net income	$ 5,664	$ 3,984
Weighted average units outsanding:
Basic and diluted (shares)	12,686,115	12,686,115
Net income per limited partner unit:
Income per limited partner unit (usd per share)	$ 0.45	$ 0.31
IDR Holders [Member]
Limited Partners' Capital Account [Line Items]
Distribution declared to IDR holders	$ 2	$ 0
Net income in excess of distribution	0	0
Net income	$ 2	$ 0

Related Party Transactions (Sal

Related Party Transactions (Sales to Related Parties) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Related Party Transaction [Line Items]
Net sales - Westlake	$ 231,260	$ 208,913
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Net sales - Westlake	$ 231,260	$ 208,913

Related Party Transactions (Cos

Related Party Transactions (Cost of Sales from Related Parties) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Related Party Transaction [Line Items]
Total charges from related parties in cost of sales	$ 142,190	$ 162,164
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Feedstock purchased from Westlake and included in cost of sales	66,108	80,819
Other charges from Westlake and included in cost of sales	20,453	13,896
Total charges from related parties in cost of sales	$ 86,561	$ 94,715

Related Party Transactions (Ser

Related Party Transactions (Services from Related Parties Included in SG&A Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Services received from Westlake and included in selling, general and administrative expenses	$ 5,468	$ 5,148

Related Party Transactions (Goo

Related Party Transactions (Goods and Services from Related Parties that have been Capitalized) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Goods and services purchased from Westlake and capitalized as assets	$ 2,007	$ 962

Related Party Transactions (Acc

Related Party Transactions (Accounts Receivable from and Accounts Payable to Related Parties) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Accounts receivable, net—Westlake	$ 56,043	$ 39,655
Accounts payable—Westlake	(7,290)	(15,550)
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Accounts receivable, net—Westlake	56,043	39,655
Accounts payable—Westlake	$ (7,290)	$ (15,550)

Related Party Transactions (Deb

Related Party Transactions (Debt Payable to Related Parties) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Interest on related party debt payable	$ 1,231	$ 1,376
Long-term debt payable to Westlake	443,525		$ 384,006
Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Interest capitalized	2,386	1,215
Long-term debt payable to Westlake	443,525		384,006
Other income (expense) | Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Interest on related party debt payable	1,231	$ 1,376
Accrued Liabilities [Member] | Affiliated Entity [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Accrued interest on related party debt	3,600		2,879
Senior Notes [Member] | Westlake [Member]
Related Party Transaction [Line Items]
Unamortized discount and debt issuance costs	$ 6,589		$ 6,741

Related Party Transactions (Gen

Related Party Transactions (General) (Details) - Westlake [Member] - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Senior unsecured revolving credit facility [Member]
Related Party Transaction [Line Items]
Outstanding letters of credit	$ 30,445	$ 30,098
Senior Notes [Member]
Related Party Transaction [Line Items]
Outstanding debt	754,000
Unamortized discount and debt issuance costs	$ 6,589	$ 6,741

Related Party Transactions (Sit

Related Party Transactions (Site Lease Agreements) (Details) - Westlake Chemical OpCo LP [Member] - Affiliated Entity [Member] - Site Lease Agreement [Member]	Aug. 04, 2014lease	Mar. 31, 2016USD ($)
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 Wes51

Long-term Debt Payable to Westlake (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Long-term debt payable to Westlake	$ 443,525	$ 384,006
Weighted average interest rate	3.41%	3.30%
Limited Partner [Member] | 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] | 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	$ 276,409	$ 216,890
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 Comprehensi52

Accumulated Other Comprehensive (Loss) Income (Details) - Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at end of period	$ (451)	$ 280
Interest rate contract - Other comprehensive loss before reclassification	(827)
Interest rate contract - Amounts reclassified to net income	$ 96

Derivative Instruments (Details

Derivative Instruments (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Ineffective portion of a derivative instrument	$ 0
Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Change in value recognized in other comprehensive loss	827,000
Interest Rate Contract [Member] | Cash Flow Hedging [Member] | Deferred charges and other assets, net [Member]
Derivative [Line Items]
Fair value of interest rate contract	0	$ 436,000
Interest Rate Contract [Member] | Cash Flow Hedging [Member] | Other Liabilities [Member]
Derivative [Line Items]
Fair value of interest rate contract	312,000	$ 0
Interest Rate Contract [Member] | Interest Expense [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Loss recognized in statement of operations	$ (96,000)

Derivative Instruments (Ineffec

Derivative Instruments (Ineffective Portion) (Details)	3 Months Ended
	Mar. 31, 2016USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Ineffective portion of a derivative instrument	$ 0

Fair Value Measurements (Summar

Fair Value Measurements (Summary of Assets and Liabilities Accounted at Fair Value on Recurring and Nonrecurring Basis) (Details) - Interest Rate Contract [Member] - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability - Interest rate contract	$ (312)
Asset - Interest rate contract		$ 436
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability - Interest rate contract	$ (312)
Asset - Interest rate contract		$ 436

Fair Value Measurements (Summ56

Fair Value Measurements (Summary of Carrying and Fair Values of Long Term Debt) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt payable to Westlake, carrying value	$ 443,525	$ 384,006
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
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	273,324	215,738
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	276,409	216,890
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	130,814	130,439
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

Income Taxes (Detail)

Income Taxes (Detail)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Effective income tax rate	0.40%	0.50%

Supplemental Information (Detai

Supplemental Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Accrued Liabilities [Abstract]
Accrued liabilities	$ 36,627		$ 23,407
Accrued capital expenditures	27,004		$ 14,745
Related Party Transaction [Line Items]
Increase (reduction) in capital expenditure accrual	$ (13,719)	$ (545)

Major Customer and Concentrat59

Major Customer and Concentration Risk (Details)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net sales [Member] | Customer Concentration Risk [Member] | Westlake [Member] | Affiliated Entity [Member]
Concentration Risk [Line Items]
Concentration risk percentage of net sales	91.60%	80.90%

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Thousands	3 Months Ended	12 Months Ended	104 Months Ended
	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Mar. 31, 2016USD ($)
Loss Contingencies [Line Items]
Number of Flares	3
Loss Contingency, Claims Settled, Number	2
Unfavorable Regulatory Action [Member]
Loss Contingencies [Line Items]
Possible amount of claims in settlement for compliance violations	$ 100		$ 100
Settled Litigation [Member]
Loss Contingencies [Line Items]
Litigation Settlement, Amount	$ 192
Goodrich and PolyOne [Member]
Loss Contingencies [Line Items]
Costs incurred for environmental remediation services		$ 2,210
Goodrich and PolyOne [Member] | Settled Litigation [Member]
Loss Contingencies [Line Items]
Percentage of costs related to environmental issues to be paid by PolyOne			100.00%
Minimum number of years between arbitrations			5 years
Goodrich and PolyOne [Member] | Pending Litigation [Member]
Loss Contingencies [Line Items]
Reimbursement of remediation costs sought by PolyOne			$ 1,400

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands	Apr. 27, 2016	Mar. 31, 2016	Mar. 31, 2015
IDR Holders [Member]
Subsequent Event [Line Items]
Distribution declared to IDR holders		$ 2	$ 0
Cash Distribution [Member] | IDR Holders [Member]
Subsequent Event [Line Items]
Distribution declared to IDR holders		$ 2	$ 0
Cash Distribution [Member] | IDR Holders [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Distribution declared to IDR holders	$ 2
Cash Distribution [Member] | Common And Subordinated Units [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Distribution declared per unit	$ 0.3168