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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2014	Oct. 31, 2014
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q3
Trading Symbol	WLKP
Entity Registrant Name	WESTLAKE CHEMICAL PARTNERS LP
Entity Central Index Key	0001604665
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

Combined and Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2013
Current assets
Cash and cash equivalents	$ 89,988
Accounts receivable, net—Westlake	28,500
Accounts receivable, net—third parties	29,606
Inventories	5,551
Prepaid expenses and other current assets	303
Deferred income taxes	0
Total current assets	153,948
Property, plant and equipment, net	806,648
Equity investments	0
Other assets, net
Intangible assets, net	5,814
Deferred charges and other assets	55,865
Total other assets, net	61,679
Total assets	1,022,275
Current liabilities
Accounts payable—Westlake	18,127
Accounts payable—third parties	12,827
Accrued liabilities	3,999
Total current liabilities	34,953
Long-term debt payable to Westlake	188,523	$ 252,973
Deferred income taxes	1,507
Other liabilities	5
Total liabilities	224,988
Commitments and contingencies (Notes 10 and 16)
NET INVESTMENT
Net investment	0
Partners' capital	83,573
Noncontrolling interest in OpCo	713,714
Total equity	797,287	455,432
Total liabilities and equity	1,022,275
Predecessor [Member]
Current assets
Cash and cash equivalents		0
Accounts receivable, net—Westlake		0
Accounts receivable, net—third parties		71,812
Inventories		116,377
Prepaid expenses and other current assets		257
Deferred income taxes		4,448
Total current assets		192,894
Property, plant and equipment, net		762,972
Equity investments		10,411
Other assets, net
Intangible assets, net		5,873
Deferred charges and other assets		69,324
Total other assets, net		75,197
Total assets		1,041,474
Current liabilities
Accounts payable—Westlake		0
Accounts payable—third parties		122,564
Accrued liabilities		26,688
Total current liabilities		149,252
Long-term debt payable to Westlake		252,973
Deferred income taxes		182,855
Other liabilities		962
Total liabilities		586,042
Commitments and contingencies (Notes 10 and 16)
NET INVESTMENT
Net investment		455,432
Partners' capital		455,432
Noncontrolling interest in OpCo		0
Total equity	0	455,432
Total liabilities and equity		1,041,474
Limited Partner [Member] \| Common units [Member] \| Public [Member]
NET INVESTMENT
Limited Partners' Capital Account	288,487
Total equity	288,487
Limited Partner [Member] \| Common units [Member] \| Public [Member] \| Predecessor [Member]
NET INVESTMENT
Limited Partners' Capital Account		0
Limited Partner [Member] \| Common units [Member] \| Westlake [Member]
NET INVESTMENT
Limited Partners' Capital Account	3,828
Total equity	3,828
Limited Partner [Member] \| Common units [Member] \| Westlake [Member] \| Predecessor [Member]
NET INVESTMENT
Limited Partners' Capital Account		0
Limited Partner [Member] \| Subordinated units [Member] \| Westlake [Member]
NET INVESTMENT
Limited Partners' Capital Account	33,830
Total equity	33,830
Limited Partner [Member] \| Subordinated units [Member] \| Westlake [Member] \| Predecessor [Member]
NET INVESTMENT
Limited Partners' Capital Account		0
General Partner [Member] \| Westlake [Member]
NET INVESTMENT
General Partners' Capital Account	(242,572)
Total equity	$ (242,572)
General Partner [Member] \| Westlake [Member] \| Predecessor [Member]
NET INVESTMENT
General Partners' Capital Account		$ 0

Consolidated Balance Sheets (Parenthetical) - shares	Sep. 30, 2014	Dec. 31, 2013
Common units [Member] \| Westlake [Member]
Units issued	1,436,115	0
Units outstanding	1,436,115	0
Common units [Member] \| Public [Member]
Units issued	12,937,500	0
Units outstanding	12,937,500	0
Subordinated units [Member] \| Westlake [Member]
Units issued	12,686,115	0
Units outstanding	12,686,115	0

Combined and Consolidated Statements of Operations - USD ($) $ in Thousands	2 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net sales - Westlake		$ 289,601		$ 1,088,561
Net co-product, ethylene and feedstock sales—third parties		102,407		387,596
Net sales		392,008		1,476,157
Cost of sales		227,015		832,304
Gross profit		164,993		643,853
Services received from Westlake and included in selling, general and administrative expenses		8,860		22,803
Income from operations		156,133		621,050
Other income (expense)
Interest expense—Westlake		(2,137)		(9,833)
Other income, net		486		3,135
Income before income taxes		154,482		614,352
Provision for income taxes		36,309		198,461
Net income	$ 54,557	$ 118,173		415,891	$ 402,340
Less: Net income attributable to noncontrolling interest in OpCo	49,542
Limited partners' interest in net income subsequent to IPO	$ 5,015			$ 415,891
Net income attributable to Westlake Chemical Partners LP subsequent to initial public offering per limited partner unit (basic and diluted)
Income per limited partner unit	$ 0.19
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding	27,059,730
Common units [Member]
Other income (expense)
Limited partners' interest in net income subsequent to IPO	$ 2,664
Net income attributable to Westlake Chemical Partners LP subsequent to initial public offering per limited partner unit (basic and diluted)
Income per limited partner unit	$ 0.19
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding	14,373,615
Subordinated units [Member]
Other income (expense)
Limited partners' interest in net income subsequent to IPO	$ 2,351
Net income attributable to Westlake Chemical Partners LP subsequent to initial public offering per limited partner unit (basic and diluted)
Income per limited partner unit	$ 0.19
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding	12,686,115
Public [Member] \| Common units [Member]
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding	12,937,500
Westlake [Member] \| Common units [Member]
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding	1,436,115
Westlake [Member] \| Subordinated units [Member]
Weighted average limited partner units outstanding (basic and diluted)
Weighted average limited partner units outstanding	12,686,115
Predecessor [Member]
Net sales - Westlake			$ 391,801		1,195,870
Net co-product, ethylene and feedstock sales—third parties			148,332		369,939
Net sales			540,133		1,565,809
Cost of sales			327,152		924,663
Gross profit			212,981		641,146
Services received from Westlake and included in selling, general and administrative expenses			6,391		19,326
Income from operations			206,590		621,820
Other income (expense)
Interest expense—Westlake			(2,295)		(4,893)
Other income, net			1,162		6,422
Income before income taxes			205,457		623,349
Provision for income taxes			72,876		221,009
Net income			$ 132,581		402,340
Limited partners' interest in net income subsequent to IPO					$ 402,340

Combined and Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Noncontrolling Interest in OpCo [Member]	Westlake [Member] General Partner [Member]	Common units [Member] Public [Member] Limited Partner [Member]	Common units [Member] Westlake [Member] Limited Partner [Member]	Subordinated units [Member] Westlake [Member] Limited Partner [Member]
Equity, beginning balance (Predecessor [Member]) at Dec. 31, 2012	$ 273,812
Equity, beginning balance at Dec. 31, 2012	273,812
Contribution of debt payable to Westlake into net investment \| Predecessor [Member]	238,600
Contribution of debt payable to Westlake into net investment	238,600
Net income for the period \| Predecessor [Member]	402,340
Net income for the period	402,340
Net distributions to Westlake \| Predecessor [Member]	(421,991)
Net distributions to Westlake	(421,991)
Equity, ending balance (Predecessor [Member]) at Sep. 30, 2013	492,761
Equity, ending balance at Sep. 30, 2013	492,761
Equity, beginning balance (Predecessor [Member]) at Dec. 31, 2013	455,432
Equity, beginning balance at Dec. 31, 2013	455,432
Net income for the period	415,891
Proceeds from initial public offering, net of finance and other offering costs	286,088
Distribution to the noncontrolling interest in OpCo	(151,729)	$ (151,729)
Equity, ending balance (Predecessor [Member]) at Sep. 30, 2014	0
Equity, ending balance at Sep. 30, 2014	$ 797,287	$ 713,714	$ (242,572)	$ 288,487	$ 3,828	$ 33,830

Combined and Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operating activities
Net income	$ 415,891
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	58,501
Provision for (recovery of) doubtful accounts	65
Loss from disposition of fixed assets	1,244
Deferred income taxes	8,267
Equity in income of joint venture, net of dividends	1,073
Changes in operating assets and liabilities
Accounts receivable	(23,637)
Increase (Decrease) in Accounts Receivable, Related Parties	10,373
Inventories	25,769
Prepaid expenses and other current assets	(715)
Accounts payable	(8,226)
Accrued liabilities	7,633
Other, net	10,498
Net cash provided by operating activities	485,990
Cash flows from investing activities
Additions to property, plant and equipment	(144,348)
Settlements of derivative instruments	(133)
Net cash used for investing activities	(144,481)
Cash flows from financing activities
Proceeds from debt payable to Westlake	141,161
Repayment of debt payable to Westlake with proceeds from the initial public offering	(78,940)
Net proceeds from issuance of common units	286,088
Proceeds from initial public offering distributed to Westlake	(151,729)
Net distributions to Westlake prior to initial public offering	(448,101)
Net cash used for financing activities	(251,521)
Net increase in cash	89,988
Cash at beginning of period	0
Cash at end of period	$ 89,988
Predecessor [Member]
Cash flows from operating activities
Net income		$ 402,340
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		54,539
Provision for (recovery of) doubtful accounts		(66)
Loss from disposition of fixed assets		1,892
Deferred income taxes		27,253
Equity in income of joint venture, net of dividends		84
Changes in operating assets and liabilities
Accounts receivable		22,745
Increase (Decrease) in Accounts Receivable, Related Parties		0
Inventories		(22,216)
Prepaid expenses and other current assets		(346)
Accounts payable		7,595
Accrued liabilities		(23,730)
Other, net		(54,562)
Net cash provided by operating activities		415,528
Cash flows from investing activities
Additions to property, plant and equipment		(158,869)
Settlements of derivative instruments		(2,297)
Net cash used for investing activities		(161,166)
Cash flows from financing activities
Proceeds from debt payable to Westlake		167,629
Repayment of debt payable to Westlake with proceeds from the initial public offering		0
Net proceeds from issuance of common units		0
Proceeds from initial public offering distributed to Westlake		0
Net distributions to Westlake prior to initial public offering		(421,991)
Net cash used for financing activities		(254,362)
Net increase in cash		0
Cash at beginning of period		0
Cash at end of period		$ 0

Business and Basis of Presentation

9 Months Ended

Sep. 30, 2014

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Business and Basis of Presentation

Description of Business

Westlake Chemical Partners LP (the "Partnership") is a Delaware limited partnership formed in March 2014 to operate, acquire and develop ethylene production facilities and related assets. On August 4, 2014, the Partnership completed its initial public offering ("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. OpCo owns three ethylene production facilities and a common carrier ethylene pipeline (collectively, the "Contributed Assets").

Unless the context otherwise requires, references in this report to the "Predecessor" refer to Westlake Chemical Partners LP Predecessor, the Partnership's predecessor for accounting purposes and refer to the time periods prior to the IPO. References in this report to the Partnership used in the present tense or prospectively refer to Westlake Chemical Partners LP and refer to the periods subsequent to the IPO. References to "Westlake" refer collectively to Westlake Chemical Corporation and its subsidiaries, other than the Partnership, OpCo and OpCo GP.

Prior to the IPO, the Predecessor generated revenue predominantly by selling ethylene and ethylene co-products to Westlake and external customers. The Predecessor typically shipped ethylene, propylene and hydrogen via pipeline systems that connected its ethylene plants to Westlake and numerous third-party customers. The Predecessor transported its butadiene and pyrolysis gasoline by rail or truck.

At the closing of the IPO, OpCo and Westlake entered into an ethylene sales agreement (the "Ethylene Sales Agreement") pursuant to which the Partnership generates a substantial majority of its revenue. The Ethylene Sales Agreement has a 12-year initial term and a minimum commitment provision under which Westlake has agreed to purchase 95% of OpCo’s planned ethylene production each year, subject to a maximum of 3.8 billion pounds per year. This agreement represents a long-term minimum purchase commitment by Westlake with variable pricing equal to OpCo’s actual feedstock and natural gas costs and estimated other costs of producing ethylene, plus a fixed margin of $0.10 per pound, less revenue from associated co-product sales. Currently, the Partnership expects to sell 95% of its ethylene production to Westlake.

The Partnership sells ethylene production in excess of volumes sold to Westlake, as well as all of the co-products resulting from the ethylene production, including propylene, crude butadiene, pyrolysis gasoline and hydrogen, directly to third parties on either a spot or contract basis. Co-products sold to third parties continue to be transported by rail or truck. Net proceeds (after transportation and other costs) from the sales of associated co-products that result from the production of ethylene purchased by Westlake are netted against the ethylene price charged to Westlake under the Ethylene Sales Agreement thereby substantially reducing the Partnership's exposure to fluctuations in the market prices of these co-products. The Partnership’s operations consist of one reportable segment: ethylene production.

The Predecessor’s operations consisted of the entire ethylene business of Westlake, including the activities of the Contributed Assets, as well as activities which were retained by Westlake. Ethylene business activities retained by Westlake include, but are not limited to, procuring feedstock, managing inventory and commodity risk and transporting ethylene from manufacturing facilities. The Partnership’s operations consist of activities of only the Contributed Assets.

Basis of Presentation

Financial information presented for the periods prior to the IPO on August 4, 2014 consists of the Predecessor's combined financial position as of December 31, 2013, its results of operations for the three and nine months periods ended September 30, 2013 and cash flows for the nine months ended September 30, 2013. Financial information of the Predecessor is derived from the financial statements and accounting records of Westlake. Subsequent to the IPO, the Partnership’s financial position, results of operations and cash flows consist of the consolidated activities and balances of the Partnership. The Partnership's consolidated financial statements include the accounts of the Partnership and its consolidated subsidiary, OpCo.

The Partnership holds a 10.6% limited partner interest and the entire non-economic general partner interest in OpCo. The remaining 89.4% limited partner interest in OpCo is owned directly by Westlake, which has no rights to direct the activities that most significantly impact the economic performance of OpCo. As a result of the fact that substantially all of OpCo's activities are conducted on behalf of Westlake, and the fact that OpCo exhibits disproportionality of voting rights to economic interest, OpCo was deemed to be a variable interest entity. The Partnership, through its ownership of OpCo’s general partner, has the power to direct the activities that most significantly impact the economic performance of OpCo, and it also has the obligation or right to absorb losses or receive benefits from OpCo that could potentially be significant to OpCo. As such, the Partnership was determined to be OpCo’s primary beneficiary and therefore consolidates OpCo’s results of operations and financial position.

For the three and nine months ended September 30, 2014, the results of operations and changes in cash position include the Partnership’s consolidated results subsequent to the IPO and the Predecessor’s combined results prior to the IPO. For these periods, the results of operations and changes in cash flows are referred to as the Partnership’s consolidated results and changes in cash flows.

The accompanying unaudited interim combined and consolidated 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 combined and consolidated financial statements should be read in conjunction with the combined carve-out financial statements and notes thereto of the Predecessor for the fiscal year ended December 31, 2013 included in the Partnership's prospectus dated July 29, 2014 (File No. 333-195551) (the "WLKP Prospectus"), as filed with the SEC on July 31, 2014. These combined and consolidated financial statements have been prepared in conformity with the accounting principles and practices as disclosed in the notes to the combined financial statements of the Predecessor for the fiscal year ended December 31, 2013.

All financial information presented for the periods after the IPO represents the consolidated results of operations, financial position and cash flows of the Partnership. Financial information for the periods prior to the IPO represents the combined results of operations, financial position and cash flows of the Predecessor. The combined and consolidated financial statements were prepared as follows:

•

The consolidated statement of operations for the three months ended September 30, 2014 consists of the consolidated results of the Partnership for the period from August 4, 2014 through September 30, 2014 and the combined results of the Predecessor for the period from July 1, 2014 through August 3, 2014. The consolidated statement of operations for the nine months ended September 30, 2014 consists of the consolidated results of the Partnership for the period from August 4, 2014 through September 30, 2014 and the combined results of the Predecessor for the period from January 1, 2014 through August 3, 2014. The combined statements of operations for the three and nine months ended September 30, 2013 consist entirely of the combined results of the Predecessor.


•	The consolidated balance sheet as of September 30, 2014 consists of the consolidated balances of the Partnership, while the combined balance sheet as of December 31, 2013 consists of the combined balances of the Predecessor.

•

The consolidated statement of cash flows for the nine months ended September 30, 2014 consists of the consolidated results of the Partnership for the period from August 4, 2014 through September 30, 2014 and the combined results of the Predecessor for the period from January 1, 2014 through August 3, 2014. The combined statement of cash flows for the nine months ended September 30, 2013 consists entirely of the combined results of the Predecessor.

•

The consolidated statement of changes in equity for the nine months ended September 30, 2014 consists of the combined activity for the Predecessor prior to August 4, 2014, and the consolidated activity for the Partnership completed at and subsequent to the IPO on August 4, 2014. The combined statement of changes in equity for the nine months ended September 30, 2013 consists entirely of the combined activity of the Predecessor.

In the opinion of management, the accompanying unaudited combined and consolidated financial statements reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Predecessor's combined financial statements as of and for the periods ended September 30, 2013 and the Partnership’s consolidated financial statements as of and for the periods ended September 30, 2014.

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, 2014 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.

The combined statements of operations for the periods before August 4, 2014 include expense allocations for certain functions historically performed by Westlake and allocated to the ethylene business, including allocations of general corporate expenses related to finance, legal, information technology, human resources, communications, ethics and compliance, shared services, employee benefits and incentives and stock-based compensation. These allocations were based primarily on the basis of direct usage when identifiable, with the remainder allocated on the basis of fixed assets, headcount or other measure. Management believes the assumptions underlying the combined financial statements, including the assumptions regarding the allocation of expenses from Westlake, are reasonable and reflect all costs related to the operations of the Predecessor, including those incurred by Westlake on behalf of the Predecessor. Nevertheless, the combined financial statements may not include all of the expenses that would have been incurred had the Predecessor been a stand-alone company during the periods presented and may not reflect its results of operations, financial position and cash flows had the Predecessor been a stand-alone company during the periods presented.

With respect to the Predecessor, Westlake used a centralized approach to the cash management and financing of its operations. The cash generated by the Predecessor’s operations was transferred to Westlake daily, and Westlake funded the Predecessor’s operating and investing activities as needed. Accordingly, the cash and cash equivalents generated by the Predecessor’s operations that were held by Westlake were not presented in its combined financial statements for any of the periods presented. The Predecessor reflected transfers of cash to and from Westlake's cash management system as a component of "Net investment" on its combined balance sheet, and as part of "Net distributions to Westlake" on its combined statements of cash flows.

Initial Public Offering

9 Months Ended

Sep. 30, 2014

Equity [Abstract]

Initial Public Offering

Contributed Assets

In connection with the IPO, the Partnership acquired a 10.6% interest in OpCo and a 100% interest in OpCo GP. OpCo owns the Contributed Assets, as described in more detail in the WLKP Prospectus.

Other assets contributed to OpCo in conjunction with the IPO include the deferred turnaround costs associated with Lake Charles Olefins and Calvert City Olefins, co-product inventories, goodwill and other assets. Additionally, OpCo assumed $246,056 of promissory notes payable to Westlake.

The Predecessor's combined financial statements reflect certain assets, liabilities and business activities that were retained by Westlake, and therefore are not reflected in the Partnership's consolidated financial statements. Assets and liabilities which are reflected in the Predecessor's combined financial statements but which were retained by Westlake include working capital accounts, ethylene and other inventories, an equity interest in a pipeline joint venture, deferred federal income taxes, certain long-term debt payable to Westlake and other long-term liabilities. Ethylene business activities retained by Westlake include, but are not limited to, procuring feedstock, managing inventory and commodity risk and transporting ethylene from manufacturing facilities. See Note 14 for details of the Predecessor's net liabilities retained by Westlake.

Initial Public Offering

On July 30, 2014, the Partnership’s common units began trading on the New York Stock Exchange under the ticker symbol "WLKP." On August 4, 2014, the Partnership closed its IPO of 12,937,500 common units at a price to the public of $24.00 per unit ($22.53 per unit net of underwriting discount), including the 1,687,500 common units that were issued pursuant to the exercise in full of the underwriters' over-allotment option as described in the WLKP Prospectus.

In connection with the closing of the IPO, in exchange for Westlake’s contribution of a 5.8% limited partner interest in OpCo and OpCo's general partner interest to the Partnership, Westlake received:


•	1,436,115 common units and 12,686,115 subordinated units, representing an aggregate 52.2% limited partner interest in the Partnership; and


•	the Partnership's general partner interest and its incentive distribution rights.

The Partnership received net proceeds of $286,088 from the IPO, net of underwriting discounts, structuring fees and offering expenses of approximately $24,412. The Partnership used the net proceeds from the IPO to purchase an additional 4.8% limited partner interest in OpCo, resulting in the Partnership owning a 10.6% limited partner interest in OpCo. The Partnership recorded the incremental 4.8% limited partner interest in OpCo at its historical carrying value of $43,516 and the excess cash paid over historical carrying value of $242,572 as a decrease to the General partner-Westlake capital account. Accordingly, the Partnership's consolidated financial statements reflect the 89.4% limited partner interest in OpCo that was retained by Westlake as a noncontrolling interest.

From the period beginning August 4, 2012 to July 31, 2013, Westlake incurred approximately $151,729 in capital expenditures (the "Pre-August 2013 Capex") with respect to the assets contributed to OpCo. The portion of these capital expenditures incurred before January 1, 2013 was accounted for as an adjustment to Net investment, as it was funded through equity. The portion of the capital expenditures incurred from January 1, 2013 through July 31, 2013 was accounted for as a liability and is reflected as such on the Predecessor’s combined financial statements and the associated liability was retained by Westlake in connection with the closing of the IPO. During the period from August 1, 2013 through August 3, 2014, Westlake funded capital expenditures of $246,056 related to the Contributed Assets under the terms of the intercompany notes that OpCo assumed in connection with the IPO (the "August 2013 Promissory Notes"). At the close of the IPO, the outstanding balance of the August 2013 Promissory Notes was $246,056.

OpCo used the $286,088 it received from the Partnership in exchange for a 4.8% limited partner interest in OpCo to (i) establish a $55,419 turnaround reserve, (ii) reimburse $151,729 to Westlake for the Pre-August 2013 Capex, and (iii) repay $78,940 of the August 2013 Promissory Notes assumed by OpCo. Immediately after the repayment, the outstanding indebtedness payable to Westlake under the August 2013 Promissory Notes was $167,116.

Agreements with Westlake and Related Parties

The agreements described below became effective on August 4, 2014, concurrent with the closing of the IPO.

Ethylene Sales Agreement

OpCo entered into a 12-year ethylene sales agreement with Westlake (the "Ethylene Sales Agreement"). The Ethylene Sales Agreement requires Westlake to purchase a minimum volume of ethylene each year equal to 95% of OpCo’s planned ethylene production per year (the "Minimum Commitment"), subject to certain exceptions and a maximum commitment of 3.8 billion pounds per year. So long as Westlake is not in default under the Ethylene Sales Agreement, if OpCo’s actual production exceeds planned production, Westlake has the option to purchase up to 95% of the excess production (the "Excess Production Option").

The fee for each pound of ethylene purchased by Westlake from OpCo up to the Minimum Commitment in any calendar year will equal:


•	the actual price OpCo pays Westlake to purchase ethane (or other feedstock, such as propane, if applicable) to produce each pound of ethylene, subject to a specified cap and a floor on the amount of feedstock that should be needed to produce each pound of ethylene; plus


•	the actual price OpCo pays Westlake to purchase natural gas to produce each pound of ethylene, subject to a specified cap and a floor on the amount of natural gas that should be needed to produce each pound of ethylene; plus


•	OpCo’s estimated operating costs (including selling, general and administrative expenses), divided by OpCo’s planned ethylene production for the year (in pounds); plus


•	a five-year average of OpCo’s expected future maintenance capital expenditures and other turnaround expenditures, divided by OpCo’s planned ethylene production capacity for the year (in pounds); less


•	the proceeds (on a per pound of ethylene basis) received by OpCo from the sale of co-products (including, but not limited to, propylene, crude butadiene, pyrolysis gasoline and hydrogen) associated with producing the ethylene purchased by Westlake; plus


•	a $0.10 per pound margin.

The fee for the Excess Production Option, if exercised, equals OpCo’s estimated variable operating costs of producing the incremental ethylene, net of revenues from co-product sales plus a $0.10 per pound margin.

The estimated operating costs and expected future maintenance capital expenditures and other turnaround expenditures will be adjusted at the end of each year, to be applicable for the fee for the next calendar year, to reflect certain changes in forecasted costs.

The result of the fee structure is that OpCo should recover the portion of its total operating costs and maintenance capital expenditures and other turnaround expenditures corresponding to the portion of OpCo’s aggregate production that is purchased by Westlake. The Ethylene Sales Agreement has an initial term extending until December 31, 2026 and automatically renews thereafter for successive 12-month terms unless terminated.

Feedstock Supply Agreement

OpCo entered into a feedstock supply agreement with Westlake, pursuant to which Westlake agrees to sell to OpCo ethane and other feedstock in amounts sufficient for OpCo to produce the ethylene to be sold under the Ethylene Sales Agreement (the "Feedstock Supply Agreement"). The Feedstock Supply Agreement provides that OpCo obtains feedstock from Westlake, based on Westlake’s total cost of purchasing and delivering the feedstock, including applicable transportation, storage and other costs. Title and risk of loss for all feedstock purchased by OpCo through the Feedstock Supply Agreement passes to OpCo upon delivery to one of three delivery points described in the Feedstock Supply Agreement.

The Feedstock Supply Agreement has an initial term extending until December 31, 2026 and automatically renews thereafter for successive 12-month terms unless terminated by either party; provided, however, that such agreement can only be renewed in the event the Ethylene Sales Agreement is renewed simultaneously. The Feedstock Supply Agreement may, in certain circumstances, terminate concurrently with the termination of the Ethylene Sales Agreement.

Services and Secondment Agreement

OpCo entered into a services and secondment agreement with Westlake, pursuant to which OpCo provides Westlake with certain services required for the operation of Westlake’s facilities; and Westlake provides OpCo with comprehensive operating services for OpCo’s facilities, ranging from services relating to the maintenance and operations of the common facilities necessary for the operation of OpCo’s units, to making available certain shared utilities such as electricity and natural gas that are necessary for the operation of OpCo’s units. Westlake also seconded employees to OpCo to allow OpCo to operate OpCo’s facilities in an efficient and compliant manner. Such seconded employees will be under the control of OpCo while they work on OpCo’s facilities.

The services and secondment agreement has an initial 12-year term. The services and secondment agreement may be renewed thereafter upon agreement of the parties and shall automatically terminate if the Ethylene Sales Agreement terminates under certain circumstances. Westlake and OpCo each can terminate the services and secondment agreement under certain circumstances, including if the other party materially defaults on the performance of its obligations and such default continues for a 30-day period.

Site Lease Agreements

OpCo entered into two site lease agreements with Westlake pursuant to which Westlake leases to OpCo the real property underlying Lake Charles Olefins and Calvert City Olefins, respectively, and grants OpCo rights to access and use certain other portions of Westlake’s ethylene production facilities that are necessary to operate OpCo’s units at such ethylene production facilities. OpCo owes Westlake one dollar per site per year. The site lease agreements each have a term of 50 years. Each of the site lease agreements may be renewed if agreed by the parties.

Omnibus Agreement

The Partnership entered into an omnibus agreement with Westlake that addresses Westlake’s indemnification of the Partnership for certain matters, including environmental and tax matters, as well as the provision by Westlake of certain management and other general and administrative services to the Partnership and its general partner and the Partnership’s reimbursement to Westlake for such services. The omnibus agreement also addresses Westlake’s right of first refusal on any proposed transfer of the ethylene production facilities that serve Westlake’s other facilities and Westlake’s right of first refusal on any proposed transfer of the Partnership's equity interests in OpCo.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

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-Name Regulation S-X (SX)
-Number 210
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-Paragraph d
-Article 4

Reference 15: http://www.xbrl.org/2003/role/presentationRef
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-Number 210
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+ Details

Recent Accounting Pronouncements	9 Months Ended
Recent Accounting Pronouncements	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Recent Accounting Pronouncements	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. The accounting standard will be 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. Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern In August 2014, the FASB issued an accounting standards update on management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern. The new accounting guidance requires management to perform interim and annual assessments of an entity's ability to continue as a going concern within one year of the date the financial statements are issued. An entity must provide certain disclosures if "conditions or events raise substantial doubt about the entity's ability to continue as a going concern." The accounting standard will be effective for reporting periods ending after December 15, 2016 and is not expected to have an impact on the Partnership's consolidated financial position, results of operations and cash flows.

- Definition

The entire disclosure of changes in accounting principles, including adoption of new accounting pronouncements, that describes the new methods, amount and effects on financial statement line items.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6507316

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-Name Accounting Standards Codification
-Glossary Direct Effects of a Change in Accounting Principle
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6515603

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-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 01
-Paragraph b
-Subparagraph 6
-Article 10

+ Details

Accounts Receivable

9 Months Ended

Sep. 30, 2014

Accounts Receivable, Net [Abstract]

Accounts Receivable

Accounts receivable consist of the following:



	September 30, 2014		December 31, 2013
			Predecessor
Trade customers	$	29,606	$	73,594
Allowance for doubtful accounts	—		(2,105		)
	29,606		71,489
Other	—		323
Accounts receivable, net—third parties	$	29,606	$	71,812

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Inventories

9 Months Ended

Sep. 30, 2014

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	September 30, 2014		December 31, 2013
			Predecessor
Finished products	$	5,551	$	21,330
Feedstock, additives and chemicals	—		80,407
Materials and supplies	—		14,640
Inventories	$	5,551	$	116,377

Property, Plant and Equipment	9 Months Ended
Property, Plant and Equipment	Sep. 30, 2014
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment As of September 30, 2014, the Partnership had property, plant and equipment, net totaling $806,648. 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 $14,900 and $14,579 is included in cost of sales in the combined and consolidated statements of operations for the three months ended September 30, 2014 and 2013, respectively. Depreciation expense on property, plant and equipment of $45,104 and $42,930 is included in cost of sales in the combined and consolidated statements of operations for the nine months ended September 30, 2014 and 2013, respectively.

Other Assets	9 Months Ended
Other Assets	Sep. 30, 2014
Other Assets [Abstract]
Other Assets	Other Assets Amortization expense on other assets of $4,319 and $4,600 is included in the combined and consolidated statements of operations for the three months ended September 30, 2014 and 2013, respectively. Amortization expense on other assets of $13,397 and $11,609 is included in the combined and consolidated statements of operations for the nine months ended September 30, 2014 and 2013, respectively.

Net Income Per Limited Partner Unit

9 Months Ended

Sep. 30, 2014

Earnings Per Share [Abstract]

Net Income Per Limited Partner Unit

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 for the period subsequent to the IPO 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. Basic and diluted net income per unit are the same because the Partnership does not have any potentially dilutive units outstanding for the periods presented.

On October 28, 2014, the board of directors of Westlake Chemical Partners GP LLC, the Partnership's general partner, declared an initial prorated quarterly cash distribution for the period August 4, 2014, through September 30, 2014, of $0.1704 per unit, or $4,611 in total. This distribution is payable on November 25, 2014, to unit holders of record as of November 10, 2014.



	Three Months Ended September 30, 2014		Nine Months Ended September 30, 2014
Net income attributable to the Partnership subsequent to the IPO	$	5,015	$	5,015
Less:
Limited partners' distribution declared on common units	2,449		2,449
Limited partners' distribution declared on subordinated units	2,162		2,162
Net income subsequent to the IPO in excess of distribution	$	404	$	404



	Three and Nine Months Ended September 30, 2014
	Limited Partners' Common Units		Limited Partners' Subordinated Units		Incentive Distribution Rights		Total
Net income attributable to the Partnership subsequent to the IPO:
Distribution declared	$	2,449	$	2,162	$	—	$	4,611
Net income subsequent to the IPO in excess of distribution	215		189		—		404
Net income subsequent to the IPO	$	2,664	$	2,351	$	—	$	5,015
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	$	0.19	$	0.19			$	0.19

Related Party Transactions

9 Months Ended

Sep. 30, 2014

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 described in Note 2. Additionally, the Partnership and OpCo from time to time provide other services or products for which it charges Westlake a fee. Prior to the IPO, the Predecessor sold the majority of its ethylene to Westlake for use in Westlake's downstream operations.

Sales to related parties were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Net sales—Westlake	$	289,601	$	391,801	$	1,088,561	$	1,195,870

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, described in Note 2. Prior to the IPO, services provided by Westlake and included in cost of sales related primarily to services provided by employees of Westlake Management Services, Inc., a subsidiary of Westlake. The cost of services provided by employees of Westlake Management Services, Inc. were allocated to the Predecessor's operations primarily on the basis of direct usage.

Charges from related parties in cost of sales were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Feedstock purchased from Westlake and included in cost of sales	$	63,108	$	—	$	63,108	$	—
Other charges from Westlake and included in cost of sales	13,879		15,484		47,000		46,273
Total	$	76,987	$	15,484	$	110,108	$	46,273

Services from Related Parties Included in Selling, General and Administrative Expenses

Charges for services purchased by the Partnership from Westlake and included in 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. Prior to the IPO, the Predecessor was allocated costs incurred by Westlake on its behalf for similar functions. These allocations were based primarily on the basis of direct usage when identifiable, with the remainder allocated on the basis of fixed assets, headcount or other measure. Management believes the allocation of expenses incurred by Westlake on the Predecessor's behalf are reasonable and reflect all costs related to the operations of the Predecessor. Nevertheless, the financial information of the Predecessor may not have included all of the expenses that would have been incurred had the Predecessor been a stand-alone company during the periods prior to the IPO.

Charges from related parties included within selling, general and administrative expenses were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Services received from Westlake and included in selling, general and administrative expenses	$	4,283	$	4,845	$	30,538	$	29,906

Goods and Services from Related Parties that have been Capitalized

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. Prior to the IPO, salaries and benefits of Westlake Management Services, Inc. were allocated to the Predecessor primarily on the basis of direct usage.

Charges from related parties for goods and services capitalized as assets were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Goods and services purchased from Westlake and capitalized as assets	$	830	$	624	$	2,074	$	15,256

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. Prior to the IPO, ethylene sales and other transactions between the Predecessor and Westlake were settled immediately through net investment, and therefore, the Predecessor did not have related party accounts receivable or related party accounts payable balances.

The related party accounts receivable and accounts payable balances were as follows:



	September 30, 2014			December 31, 2013
				Predecessor
Accounts receivable, net—Westlake	$	28,500		$	—
Accounts payable—Westlake	(18,127		)	—

Debt Payable to Related Parties

OpCo assumed promissory notes payable to Westlake and entered into a revolving credit facility with Westlake in connection with the closing of the IPO. Prior to the IPO, the Predecessor funded capital expenditures through promissory notes payable to Westlake, a portion of which were assumed by the Partnership in connection with the IPO. See Note 10 for a description of related party debt payable balances.

Debt payable to related parties was as follows:



	September 30, 2014		December 31, 2013
Long-term debt payable to Westlake	$	188,523	$	252,973

General

OpCo, together with other subsidiaries of Westlake not included in these combined and consolidated financial statements, are guarantors under Westlake's revolving credit facility and the indentures governing its senior notes. As of September 30, 2014, Westlake had outstanding letters of credit totaling $32,399 under its revolving credit facility and $754,000 outstanding under its senior notes (less the unamortized discount of $921).

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.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

Long-term debt payable to Westlake

9 Months Ended

Sep. 30, 2014

Long-term debt payable to Westlake

Payable to Westlake

Long-term debt payable to Westlake consists of the following:



	September 30, 2014		December 31, 2013
			Predecessor
2006 Pipeline Note (variable interest rate of prime plus 0.25%, original scheduled maturity of November 30, 2016)	$	—	$	14,400
2013 Promissory Notes (variable interest rate of prime plus 1.5%, original scheduled maturity of August 1, 2023)	168,376		238,573
Senior unsecured revolving credit facility (variable interest rate of LIBOR plus 3.0%, original scheduled maturity of August 4, 2019)	20,147		—
	$	188,523	$	252,973

In 2013, three intercompany promissory notes were issued for capital expenditures incurred by Westlake on behalf of the Predecessor’s operations (together, the "2013 Promissory Notes"). For additional information on the 2013 Promissory Notes, please read Note 9 (Promissory Notes Payable to Westlake) to the audited combined carve-out financial statements for the fiscal year ended December 31, 2013 included in the WLKP Prospectus. Proceeds drawn under the 2013 Promissory Notes during the nine months ended September 30, 2014 were used to fund capital expenditures at the Predecessor’s ethylene plants. In connection with the IPO, OpCo assumed a portion of the 2013 Promissory Notes and used proceeds from the IPO to repay a portion of the balance it assumed. See Note 2 for a description of the promissory notes assumed and proceeds used to repay balances of promissory notes assumed in connection with the IPO.

In connection with the IPO on August 4, 2014, OpCo entered into a senior unsecured revolving credit facility agreement with Westlake. The credit facility accrues interest quarterly at a rate of LIBOR plus 3.0%, which may be paid-in-kind as an addition to the principal at OpCo's option.

Derivative Instruments

9 Months Ended

Sep. 30, 2014

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Instruments

Commodity Risk Management

The Predecessor used derivative instruments to reduce price volatility risk on raw materials and products as a substantial portion of its raw materials and products were commodities whose prices fluctuate as market supply and demand fundamentals change. The Predecessor employed strategies to protect against such instability, including ethylene product feedstock flexibility. The Predecessor did not use derivative instruments to engage in speculative activities. The Contributed Assets do not include the entity engaged in commodity risk management activities or any of its open derivative positions. The Partnership has not engaged in any hedging activity and did not use derivative instruments in the period subsequent to the IPO. Therefore, there are no derivative assets or liabilities reflected in the consolidated balance sheet of the Partnership as of September 30, 2014.

For derivative instruments that were designated and qualify as fair value hedges, the gains or losses on the derivative instruments, as well as the offsetting losses or gains on the hedged items attributable to the hedged risk, were included in cost of sales in the combined statements of operations for the three and nine months ended September 30, 2013. The Partnership had no derivative instruments that were designated as fair value hedges for the three and nine months ended September 30, 2014.

Gains and losses from changes in the fair value of derivative instruments that are not designated as hedging instruments were included in gross profit in the combined and consolidated statements of operations for the three and nine months ended September 30, 2014 and 2013.

The exposure on commodity derivatives used for price risk management includes the risk that the counterparty will not pay if the market declines below the established fixed price. In such case, the Partnership would lose the benefit of the derivative differential on the volume of the commodities covered. In any event, the Partnership would continue to receive the market price on the actual volume hedged. The Partnership also bears the risk that it could lose the benefit of market improvements over the fixed derivative price for the term and volume of the derivative instruments (as such improvements would accrue to the benefit of the counterparty).

Disclosures related to the Predecessor's derivative assets and derivative liabilities subject to enforceable master netting arrangements have not been presented as they are not material to the Predecessor's combined balance sheet at December 31, 2013. There were no open derivative positions at September 30, 2014.

The fair values of derivative instruments in the combined and consolidated balance sheets were as follows:



	Derivative Assets
	Balance Sheet Location	Fair Value as of
	Balance Sheet Location	September 30, 2014		December 31, 2013
				Predecessor
Not designated as hedging instruments
Commodity forward contracts	Accounts receivable, net	$	—	$	296
Total derivative assets		$	—	$	296



	Derivative Liabilities
	Balance Sheet Location	Fair Value as of
	Balance Sheet Location	September 30, 2014		December 31, 2013
				Predecessor
Not designated as hedging instruments
Commodity forward contracts	Accrued liabilities	$	—	$	176
Total derivative liabilities		$	—	$	176

The following tables reflect the impact of derivative instruments designated as fair value hedges and the related hedged items on the combined and consolidated statements of operations. For the three and nine months ended September 30, 2013, there was no material ineffectiveness with regard to the Predecessor's qualifying fair value hedges.



Derivatives in Fair Value Hedging Relationships	Location of Gain (Loss) Recognized in Income on Derivative	Three Months Ended September 30,					Nine Months Ended September 30,
Derivatives in Fair Value Hedging Relationships	Location of Gain (Loss) Recognized in Income on Derivative	2014		2013			2014		2013
				Predecessor					Predecessor
Commodity forward contracts	Cost of sales	$	—	$	(232	)	$	—	$	(342	)

Hedged Items in Fair Value Hedging Relationships	Location of Gain (Loss) Recognized in Income on Hedged Items	Three Months Ended September 30,					Nine Months Ended September 30,
Hedged Items in Fair Value Hedging Relationships		2014		2013			2014		2013
				Predecessor					Predecessor
Firm commitment designated as the hedged item	Cost of sales	$	—	$	236		$	—	$	15

The impact of derivative instruments that have not been designated as hedges in the combined and consolidated statements of operations were as follows:



Derivatives Not Designated as Hedging Instruments	Location of Gain (Loss) Recognized in Income on Derivative	Three Months Ended September 30,					Nine Months Ended September 30,
Derivatives Not Designated as Hedging Instruments	Location of Gain (Loss) Recognized in Income on Derivative	2014			2013		2014			2013
					Predecessor					Predecessor
Commodity forward contracts	Gross profit	$	(8,873	)	$	4,854	$	(9,244	)	$	9,897

See Note 12 for the fair value of derivative instruments.

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Topic 815
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+ Details

Fair Value Measurements

9 Months Ended

Sep. 30, 2014

Fair Value Disclosures [Abstract]

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.

There were no assets or liabilities accounted for at fair value on a recurring basis as of September 30, 2014. The following table summarizes, by level within the fair value hierarchy, assets and liabilities that were accounted for at fair value on a recurring basis:



	December 31, 2013
	Level 1		Level 2			Total
	Predecessor
Derivative instruments
Risk management assets - Commodity forward contracts	$	48	$	248		$	296
Risk management liabilities - Commodity forward contracts	—		(176		)	(176		)

The Level 2 measurements for the Predecessor's commodity contracts were derived using forward curves supplied by industry-recognized and unrelated third-party services. There were no transfers in or out of Levels 1 and 2 of the fair value hierarchy for the nine months ended September 30, 2014 and 2013.

In addition to the financial assets and liabilities above, 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 and combined 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 and the Predecessor's long-term debt at September 30, 2014 and December 31, 2013 are summarized in the table below. The Partnership’s long-term debt includes related party promissory notes issued to Westlake and a credit facility entered with Westlake in connection with the IPO. 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.



	September 30, 2014				December 31, 2013
	Carrying Value		Fair Value		Carrying Value		Fair Value
					Predecessor
2006 Pipeline Note	$	—	$	—	$	14,400	$	13,922
2013 Promissory Notes	168,376		168,376		238,573		238,573
Senior unsecured revolving credit facility	20,147		20,147		—		—

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2014
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 Predecessor’s operating results were included in Westlake’s consolidated U.S. federal and state income tax returns. Amounts presented in the combined financial statements prior to the IPO relate to income taxes that have been determined on a separate tax return basis, and the Predecessor’s contribution to Westlake Chemical Corporation’s net operating losses and tax credits have been included in the Predecessor’s financial statements. The effective income tax rate of the Predecessor was 35.4% for the period from January 1, 2014 through August 3, 2014. The effective income tax rate for the 2014 period prior to the IPO was above the U.S. federal statutory rate of 35.0% primarily due to state income taxes, mostly offset by the domestic manufacturing deduction and state income tax credits. The effective income tax rate of the Predecessor was 35.5% for the nine months ended September 30, 2013. The effective income tax rate for the nine months ended September 30, 2013 was above the U.S. federal statutory rate of 35.0% primarily due to state income taxes, mostly offset by the domestic manufacturing deduction and state income tax credits. The Partnership’s effective tax rate was less than one percent for the period subsequent to the IPO.

Supplemental Information

9 Months Ended

Sep. 30, 2014

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Supplemental Information

Net Liabilities Retained by Westlake

Net liabilities of the Predecessor that were not assumed by OpCo in connection with the IPO are composed of the following:



Accounts receivable, net—third parties	$	64,650
Inventories	85,057
Prepaid expenses and other current assets	669
Deferred income taxes	4,448
Property, plant and equipment, net	62,886
Equity investments	9,338
Accounts payable—third parties	(101,671		)
Accrued liabilities	(37,451		)
Deferred income taxes	(189,615		)
Long-term debt payable to Westlake	(137,103		)
Other liabilities	(914		)
Total	$	(239,706	)

Non-cash Operating Activity

The Partnership or the Predecessor settled $2,089 and $2,168 of its total interest expense incurred on long-term debt payable to Westlake as an addition to principal on debt outstanding for the three months ended September 30, 2014 and 2013, respectively. The Partnership or the Predecessor settled $9,530 and $4,498 of its total interest expense incurred on long-term debt payable to Westlake as an addition to principal on long-term debt payable to Westlake for the nine months ended September 30, 2014 and 2013, respectively. Interest incurred on long-term debt payable to Westlake discussed in Note 10 may be settled through additions to principal outstanding, at the Partnership's option. For additional information on the 2013 Promissory Notes, please read Note 9 (Promissory Notes Payables to Westlake) to the audited combined carve-out financial statements for the fiscal year ended December 31, 2013 included in the WLKP Prospectus.

Non-cash Investing Activity

The change in capital expenditure accrual reducing additions to property, plant and equipment was $8,564 for the nine months ended September 30, 2014. The change in capital expenditure accrual reducing additions to property, plant and equipment was $9,512 for the nine months ended September 30, 2013.

Non-cash Financing Activity

Related party notes payable to Westlake of $238,600 were deemed settled through net investment in 2013. The non-cash settlement was recorded as an increase in Westlake’s net investment in the Predecessor. No cash was transferred in connection with the deemed settlement of these notes. See Note 9 (Promissory Notes Payable to Westlake) to the audited combined carve-out financial statements for the fiscal year ended December 31, 2013 included in the WLKP Prospectus, for a description of the intercompany debt settled in 2013 between the Predecessor and Westlake.

Major Customer and Concentration Risk	9 Months Ended
Major Customer and Concentration Risk	Sep. 30, 2014
Risks and Uncertainties [Abstract]
Major Customer and Concentration of Credit Risk	Major Customer and Concentration of Credit Risk During the three months ended September 30, 2014 and 2013, Westlake accounted for approximately 73.9% and 72.5%, respectively, of the Partnership's or the Predecessor's net sales. During the nine months ended September 30, 2014 and 2013, Westlake accounted for approximately 73.7% and 76.4%, respectively, of the Partnership’s or the Predecessor's net sales.

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2014
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 it to mitigate the effects of contamination caused by the release or disposal of hazardous substances into the environment. Under one law, 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 several of 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. Contract Disputes with Goodrich and PolyOne. In connection with the 1990 and 1997 acquisitions of the Goodrich Corporation ("Goodrich") chemical manufacturing complex in Calvert City, Goodrich agreed to indemnify the Predecessor for any liabilities related to preexisting contamination at the complex. For its part, the Predecessor agreed to indemnify Goodrich for post-closing contamination caused by the Predecessor’s operations. The soil and groundwater at the complex, which does not include the Predecessor’s nearby PVC facility, had been extensively contaminated under Goodrich’s operations. In 1993, Goodrich spun off the Predecessor of PolyOne Corporation ("PolyOne"), and the Predecessor assumed Goodrich’s indemnification obligations relating to preexisting contamination. In 2003, litigation arose among the Predecessor, 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 PolyOne agreed to assume 100% of responsibility for site contamination subject to the right to seek reallocation through an arbitration process. By letter dated March 16, 2010, PolyOne notified Westlake that it was initiating an arbitration proceeding under the settlement agreement. This arbitration is currently stayed. State Administrative Proceedings. There are several administrative proceedings in Kentucky pertaining to the Calvert City site involving Goodrich’s Resource Conservation and Recovery Act permit which requires Goodrich to remediate contamination at the site. Site contamination is currently being addressed under the U.S. Comprehensive Environmental Response, Compensation, and Liability Act by the Predecessor, Goodrich and PolyOne pursuant to an Administrative Settlement with the U.S. Environmental Protection Agency which requires the parties to conduct a remedial investigation and feasibility study. As a result, the state proceedings are currently stayed and corrective action under the permit has been suspended. Monetary Relief. Except as noted above with respect to the settlement of the contract litigation among the Predecessor, Goodrich and PolyOne, there has been no determination of responsibility or any allocation of the costs of remediation among the various parties that are involved in the judicial and administrative proceedings discussed above. At this time, the Partnership is not able to estimate the loss or reasonable possible loss, if any, on the Predecessor’s financial statements that could result from the resolution of these proceedings. These matters will have no impact on the Partnership’s financial statements since Westlake has agreed to indemnify OpCo for any liabilities related to pre-existing contamination at the Calvert City plant, and OpCo has agreed to indemnity Westlake for any post-closing contamination caused by its operations of the Calvert City plant. In addition to the matters described above, the Partnership is involved in various routine legal proceedings incidental to the conduct of its business. The Partnership does not believe that any of these routine legal proceedings will have a material adverse effect on its financial condition, results of operations or cash flows.

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2014
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Distribution On October 28, 2014, the board of directors of Westlake Chemical Partners GP LLC, the Partnership's general partner, declared an initial prorated quarterly distribution for the period August 4, 2014 through September 30, 2014 of $0.1704 per unit, or $4,611 in total, that will be paid November 25, 2014 to unitholders of record on November 10, 2014. General Subsequent events were evaluated through the date on which the financial statements were issued.

Business and Basis of Presentation (Policies)

9 Months Ended

Sep. 30, 2014

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of Financial Statements

Basis of Presentation

•


•	The consolidated balance sheet as of September 30, 2014 consists of the consolidated balances of the Partnership, while the combined balance sheet as of December 31, 2013 consists of the combined balances of the Predecessor.

•

Accounts Receivable (Tables)

9 Months Ended

Sep. 30, 2014

Accounts Receivable, Net [Abstract]

Schedule Of Accounts Receivable

Accounts receivable consist of the following:



	September 30, 2014		December 31, 2013
			Predecessor
Trade customers	$	29,606	$	73,594
Allowance for doubtful accounts	—		(2,105		)
	29,606		71,489
Other	—		323
Accounts receivable, net—third parties	$	29,606	$	71,812

Inventories (Tables)

9 Months Ended

Sep. 30, 2014

Inventory Disclosure [Abstract]

Schedule Of Inventory

Inventories consist of the following:



	September 30, 2014		December 31, 2013
			Predecessor
Finished products	$	5,551	$	21,330
Feedstock, additives and chemicals	—		80,407
Materials and supplies	—		14,640
Inventories	$	5,551	$	116,377

Net Income Per Limited Partner Unit (Tables)

9 Months Ended

Sep. 30, 2014

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted



	Three Months Ended September 30, 2014		Nine Months Ended September 30, 2014
Net income attributable to the Partnership subsequent to the IPO	$	5,015	$	5,015
Less:
Limited partners' distribution declared on common units	2,449		2,449
Limited partners' distribution declared on subordinated units	2,162		2,162
Net income subsequent to the IPO in excess of distribution	$	404	$	404



	Three and Nine Months Ended September 30, 2014
	Limited Partners' Common Units		Limited Partners' Subordinated Units		Incentive Distribution Rights		Total
Net income attributable to the Partnership subsequent to the IPO:
Distribution declared	$	2,449	$	2,162	$	—	$	4,611
Net income subsequent to the IPO in excess of distribution	215		189		—		404
Net income subsequent to the IPO	$	2,664	$	2,351	$	—	$	5,015
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	$	0.19	$	0.19			$	0.19

Related Party Transactions (Tables)

9 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Schedule of Related Party Transactions

Long-term debt payable to Westlake consists of the following:



	September 30, 2014		December 31, 2013
			Predecessor
2006 Pipeline Note (variable interest rate of prime plus 0.25%, original scheduled maturity of November 30, 2016)	$	—	$	14,400
2013 Promissory Notes (variable interest rate of prime plus 1.5%, original scheduled maturity of August 1, 2023)	168,376		238,573
Senior unsecured revolving credit facility (variable interest rate of LIBOR plus 3.0%, original scheduled maturity of August 4, 2019)	20,147		—
	$	188,523	$	252,973

Charges from related parties for goods and services capitalized as assets were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Goods and services purchased from Westlake and capitalized as assets	$	830	$	624	$	2,074	$	15,256

The related party accounts receivable and accounts payable balances were as follows:



	September 30, 2014			December 31, 2013
				Predecessor
Accounts receivable, net—Westlake	$	28,500		$	—
Accounts payable—Westlake	(18,127		)	—

Sales to related parties were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Net sales—Westlake	$	289,601	$	391,801	$	1,088,561	$	1,195,870

Charges from related parties in cost of sales were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Feedstock purchased from Westlake and included in cost of sales	$	63,108	$	—	$	63,108	$	—
Other charges from Westlake and included in cost of sales	13,879		15,484		47,000		46,273
Total	$	76,987	$	15,484	$	110,108	$	46,273

Charges from related parties included within selling, general and administrative expenses were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Services received from Westlake and included in selling, general and administrative expenses	$	4,283	$	4,845	$	30,538	$	29,906

Debt payable to related parties was as follows:



	September 30, 2014		December 31, 2013
Long-term debt payable to Westlake	$	188,523	$	252,973

Long-term debt payable to Westlake (Tables)

9 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Schedule of Related Party Transactions

Long-term debt payable to Westlake consists of the following:



	September 30, 2014		December 31, 2013
			Predecessor
2006 Pipeline Note (variable interest rate of prime plus 0.25%, original scheduled maturity of November 30, 2016)	$	—	$	14,400
2013 Promissory Notes (variable interest rate of prime plus 1.5%, original scheduled maturity of August 1, 2023)	168,376		238,573
Senior unsecured revolving credit facility (variable interest rate of LIBOR plus 3.0%, original scheduled maturity of August 4, 2019)	20,147		—
	$	188,523	$	252,973

Charges from related parties for goods and services capitalized as assets were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Goods and services purchased from Westlake and capitalized as assets	$	830	$	624	$	2,074	$	15,256

The related party accounts receivable and accounts payable balances were as follows:



	September 30, 2014			December 31, 2013
				Predecessor
Accounts receivable, net—Westlake	$	28,500		$	—
Accounts payable—Westlake	(18,127		)	—

Sales to related parties were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Net sales—Westlake	$	289,601	$	391,801	$	1,088,561	$	1,195,870

Charges from related parties in cost of sales were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Feedstock purchased from Westlake and included in cost of sales	$	63,108	$	—	$	63,108	$	—
Other charges from Westlake and included in cost of sales	13,879		15,484		47,000		46,273
Total	$	76,987	$	15,484	$	110,108	$	46,273

Charges from related parties included within selling, general and administrative expenses were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
			Predecessor				Predecessor
Services received from Westlake and included in selling, general and administrative expenses	$	4,283	$	4,845	$	30,538	$	29,906

Debt payable to related parties was as follows:



	September 30, 2014		December 31, 2013
Long-term debt payable to Westlake	$	188,523	$	252,973

Derivative Instruments (Tables)

9 Months Ended

Sep. 30, 2014

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Fair Values of Derivatives Instruments in Consolidated Balance Sheets

The fair values of derivative instruments in the combined and consolidated balance sheets were as follows:



	Derivative Assets
	Balance Sheet Location	Fair Value as of
	Balance Sheet Location	September 30, 2014		December 31, 2013
				Predecessor
Not designated as hedging instruments
Commodity forward contracts	Accounts receivable, net	$	—	$	296
Total derivative assets		$	—	$	296



	Derivative Liabilities
	Balance Sheet Location	Fair Value as of
	Balance Sheet Location	September 30, 2014		December 31, 2013
				Predecessor
Not designated as hedging instruments
Commodity forward contracts	Accrued liabilities	$	—	$	176
Total derivative liabilities		$	—	$	176

Impact of Derivatives Instruments Designated as Fair Value Hedges



Derivatives in Fair Value Hedging Relationships	Location of Gain (Loss) Recognized in Income on Derivative	Three Months Ended September 30,					Nine Months Ended September 30,
Derivatives in Fair Value Hedging Relationships	Location of Gain (Loss) Recognized in Income on Derivative	2014		2013			2014		2013
				Predecessor					Predecessor
Commodity forward contracts	Cost of sales	$	—	$	(232	)	$	—	$	(342	)

Hedged Items in Fair Value Hedging Relationships	Location of Gain (Loss) Recognized in Income on Hedged Items	Three Months Ended September 30,					Nine Months Ended September 30,
Hedged Items in Fair Value Hedging Relationships		2014		2013			2014		2013
				Predecessor					Predecessor
Firm commitment designated as the hedged item	Cost of sales	$	—	$	236		$	—	$	15

Impact of Derivative Instruments Not Designated as Fair Value Hedges

The impact of derivative instruments that have not been designated as hedges in the combined and consolidated statements of operations were as follows:



Derivatives Not Designated as Hedging Instruments	Location of Gain (Loss) Recognized in Income on Derivative	Three Months Ended September 30,					Nine Months Ended September 30,
Derivatives Not Designated as Hedging Instruments	Location of Gain (Loss) Recognized in Income on Derivative	2014			2013		2014			2013
					Predecessor					Predecessor
Commodity forward contracts	Gross profit	$	(8,873	)	$	4,854	$	(9,244	)	$	9,897

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2014

Fair Value Disclosures [Abstract]

Summary Of Assets And Liabilities Accounted At Fair Value On A Recurring Basis

The following table summarizes, by level within the fair value hierarchy, assets and liabilities that were accounted for at fair value on a recurring basis:



	December 31, 2013
	Level 1		Level 2			Total
	Predecessor
Derivative instruments
Risk management assets - Commodity forward contracts	$	48	$	248		$	296
Risk management liabilities - Commodity forward contracts	—		(176		)	(176		)

Summary Of Carrying And Fair Values Of Long-Term Debt

The carrying and fair values of the Partnership's and the Predecessor's long-term debt at September 30, 2014 and December 31, 2013 are summarized in the table below. The Partnership’s long-term debt includes related party promissory notes issued to Westlake and a credit facility entered with Westlake in connection with the IPO. 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.



	September 30, 2014				December 31, 2013
	Carrying Value		Fair Value		Carrying Value		Fair Value
					Predecessor
2006 Pipeline Note	$	—	$	—	$	14,400	$	13,922
2013 Promissory Notes	168,376		168,376		238,573		238,573
Senior unsecured revolving credit facility	20,147		20,147		—		—

Supplemental Information (Tables)

9 Months Ended

Sep. 30, 2014

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Liabilities Retained By Parent Company [Table Text Block]

Net liabilities of the Predecessor that were not assumed by OpCo in connection with the IPO are composed of the following:



Accounts receivable, net—third parties	$	64,650
Inventories	85,057
Prepaid expenses and other current assets	669
Deferred income taxes	4,448
Property, plant and equipment, net	62,886
Equity investments	9,338
Accounts payable—third parties	(101,671		)
Accrued liabilities	(37,451		)
Deferred income taxes	(189,615		)
Long-term debt payable to Westlake	(137,103		)
Other liabilities	(914		)
Total	$	(239,706	)

Business and Basis of Presentation (Details) lb in Billions		9 Months Ended
Business and Basis of Presentation (Details) lb in Billions	Aug. 04, 2014 production_facility lb $ / lb shares	Sep. 30, 2014 Segment
Limited Partners' Capital Account [Line Items]
Number of reportable segments \| Segment		1
Westlake Chemical OpCo LP [Member] \| Affiliated Entity [Member]
Limited Partners' Capital Account [Line Items]
Limited partner interest	10.60%
Westlake Chemical OpCo GP LLC [Member] \| Limited Liability Company [Member]
Limited Partners' Capital Account [Line Items]
Limited partner interest	100.00%
Westlake Chemical OpCo LP [Member]
Limited Partners' Capital Account [Line Items]
Number of ethylene production facilities \| production_facility	3
Westlake [Member] \| Westlake Chemical OpCo LP [Member] \| Majority-Owned Subsidiary, Unconsolidated [Member]
Limited Partners' Capital Account [Line Items]
Limited partner interest	89.40%
Westlake [Member] \| Westlake Chemical OpCo LP [Member] \| Ethylene Sales Agreement [Member] \| Investee [Member]
Limited Partners' Capital Account [Line Items]
Term of sales agreement	12 years
Minimum percentage required to be purchased	95.00%
Maximum mass required to be purchased \| lb	3.8
Purchase commitment, fixed margin on variable pricing \| $ / lb	0.10
Percentage of production expected to sell to Westlake	95.00%
Limited Partner [Member]
Limited Partners' Capital Account [Line Items]
Number of units sold in public offering \| shares	12,937,500
Limited Partner [Member] \| Westlake [Member]
Limited Partners' Capital Account [Line Items]
Limited partner interest	5.80%

Initial Public Offering (Details) $ / shares in Units, $ in Thousands, lb in Billions		2 Months Ended	9 Months Ended	12 Months Ended
	Aug. 04, 2014 USD ($) lb $ / shares $ / lb shares	Sep. 30, 2014 USD ($) shares	Sep. 30, 2014 USD ($) shares	Aug. 03, 2014 USD ($)	Jul. 31, 2013 USD ($)	Aug. 05, 2014 USD ($)	Dec. 31, 2013 shares
Limited Partners' Capital Account [Line Items]
Net proceeds from issuance of common units			$ 286,088
Payments of unit issuance costs	$ 24,412
Westlake Chemical OpCo LP [Member] \| Loans Payable [Member] \| 2013 Promissory Note [Member]
Limited Partners' Capital Account [Line Items]
Debt assumed by acquiree						$ 167,116
Westlake Chemical OpCo LP [Member] \| IPO [Member]
Limited Partners' Capital Account [Line Items]
Net proceeds from issuance of common units	286,088
Westlake Chemical OpCo LP [Member] \| IPO [Member] \| Preformation Capital Expenditure [Member]
Limited Partners' Capital Account [Line Items]
Use of proceeds from public offering	151,729
Westlake Chemical OpCo LP [Member] \| IPO [Member] \| Cash Reserve Turnaround [Member]
Limited Partners' Capital Account [Line Items]
Use of proceeds from public offering	55,419
Westlake Chemical OpCo LP [Member] \| IPO [Member] \| Intercompany Debt [Member]
Limited Partners' Capital Account [Line Items]
Use of proceeds from public offering	$ 78,940
Westlake [Member]
Limited Partners' Capital Account [Line Items]
Excess cash paid over carrying value of partnership interest		$ 242,572
Capital expenditures				$ 246,056	$ 151,729
Common units [Member] \| Westlake [Member]
Limited Partners' Capital Account [Line Items]
Units outstanding \| shares	1,436,115
Subordinated units [Member] \| Westlake [Member]
Limited Partners' Capital Account [Line Items]
Units outstanding \| shares	12,686,115
Westlake [Member]
Limited Partners' Capital Account [Line Items]
Number of units sold in public offering \| shares	12,937,500
Price per unit \| $ / shares	$ 24.00
Price per unit, net of underwriting discount \| $ / shares	$ 22.53
Westlake [Member] \| Over-Allotment Option [Member]
Limited Partners' Capital Account [Line Items]
Number of units sold in public offering \| shares	1,687,500
Westlake [Member] \| Westlake [Member]
Limited Partners' Capital Account [Line Items]
Partnership's ownership interest	5.80%
Westlake [Member] \| OpCo and OpCo's General Partner Interest [Member]
Limited Partners' Capital Account [Line Items]
Partnership's ownership interest	52.20%
Westlake Chemical OpCo LP [Member] \| Affiliated Entity [Member]
Limited Partners' Capital Account [Line Items]
Partnership's ownership interest	10.60%
Additional ownership interest acquired	4.80%
Carrying value of additional partnership interest purchased	$ 43,516
Westlake Chemical OpCo LP [Member] \| Westlake [Member] \| Majority-Owned Subsidiary, Unconsolidated [Member]
Limited Partners' Capital Account [Line Items]
Partnership's ownership interest	89.40%
Westlake Chemical OpCo LP [Member] \| Westlake [Member] \| Ethylene Sales Agreement [Member] \| Investee [Member]
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]
Term of sales agreement	12 years
Minimum percentage required to be purchased	95.00%
Maximum mass required to be purchased \| lb	3.8
Number of years used to calculate average expenses	5 years
Purchase commitment, fixed margin on variable pricing \| $ / lb	0.10
Purchase commitment, renewal term	12 months
Westlake Chemical OpCo LP [Member] \| Westlake [Member] \| Excess Production Option [Member] \| Investee [Member]
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]
Percentage of excess production that can be purchased	95.00%
Purchase commitment, fixed margin on variable pricing \| $ / lb	0.10
Westlake Chemical OpCo LP [Member] \| Westlake [Member] \| Feedstock Supply Agreement [Member] \| Investee [Member]
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]
Related partiy transactions, term of agreements	12 months
Westlake Chemical OpCo LP [Member] \| Westlake [Member] \| Services And Secondment Agreement [Member] \| Investee [Member]
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]
Related partiy transactions, term of agreements	12 years
Related Party Transaction, Counterparty Default, Period Of Default, Allowing Termination Of Agreement	30 days
Westlake Chemical OpCo LP [Member] \| Westlake [Member] \| Site Lease Agreement [Member] \| Investee [Member]
Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract]
Related partiy transactions, term of agreements	50 years
Westlake Chemical OpCo GP LLC [Member] \| Limited Liability Company [Member]
Limited Partners' Capital Account [Line Items]
Partnership's ownership interest	100.00%
Westlake [Member] \| Westlake Chemical OpCo LP [Member] \| Loans Payable [Member] \| 2013 Promissory Note [Member] \| Investor [Member]
Limited Partners' Capital Account [Line Items]
Debt assumed by acquiree	$ 246,056
Westlake [Member] \| Common units [Member]
Limited Partners' Capital Account [Line Items]
Units outstanding \| shares		1,436,115	1,436,115				0
Westlake [Member] \| Subordinated units [Member]
Limited Partners' Capital Account [Line Items]
Units outstanding \| shares		12,686,115	12,686,115				0

Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade customers	$ 29,606
Allowance for doubtful accounts	0
Receivables from trade customers and affiliates, net	29,606
Other	0
Accounts receivable, net	$ 29,606
Predecessor [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade customers		$ 73,594
Allowance for doubtful accounts		(2,105)
Receivables from trade customers and affiliates, net		71,489
Other		323
Accounts receivable, net		$ 71,812

Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2013
Inventory [Line Items]
Finished products	$ 5,551
Feedstock, additives and chemicals	0
Materials and supplies	0
Inventories	$ 5,551
Predecessor [Member]
Inventory [Line Items]
Finished products		$ 21,330
Feedstock, additives and chemicals		80,407
Materials and supplies		14,640
Inventories		$ 116,377

Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Property, Plant and Equipment [Abstract]
Property, plant and equipment	$ 806,648		$ 806,648
Depreciation expense on property, plant and equipment	$ 14,900	$ 14,579	$ 45,104	$ 42,930

Other Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Other Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Other Assets [Member]
Amortization expense	$ 4,319	$ 4,600	$ 13,397	$ 11,609

Net Income Per Limited Partner Unit (Details) - Subsequent Event [Member] $ / shares in Units, $ in Thousands	Oct. 28, 2014 USD ($) $ / shares
Subsequent Event [Line Items]
Distribution declared per unit \| $ / shares	$ 0.1704
Distribution declared \| $	$ 4,611

Net Income Per Limited Partner Unit (Income In Excess Of Distribution) (Details) - USD ($) $ in Thousands	2 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014
Limited partners' interest in net income subsequent to IPO	$ 5,015	$ 415,891
Distribution declared	4,611
Net income subsequent to the IPO in excess of distribution	404
Common units [Member]
Limited partners' interest in net income subsequent to IPO	2,664
Distribution declared	2,449
Net income subsequent to the IPO in excess of distribution	215
Subordinated units [Member]
Limited partners' interest in net income subsequent to IPO	2,351
Distribution declared	2,162
Net income subsequent to the IPO in excess of distribution	$ 189

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Net Income
-URI http://asc.fasb.org/extlink&oid=6518256

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.19)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.18)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.22)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Other Comprehensive Income
-URI http://asc.fasb.org/extlink&oid=6519514

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e565-108580

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 19
-Article 5

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 20
-Article 9

+ Details

Net Income Per Limited Partner Unit (Basic and Diluted Income Per Limited Partner Unit) (Details) - USD ($) $ / shares in Units, $ in Thousands	2 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014
Limited Partners' Capital Account [Line Items]
Distribution declared	$ 4,611
Net income subsequent to the IPO in excess of distribution	404
Limited partners' interest in net income subsequent to IPO	$ 5,015	$ 415,891
Weighted average units outsanding:
Basic and diluted	27,059,730
Net income per limited partner unit:
Income per limited partner unit	$ 0.19
Limited Partners' Common Units [Member]
Limited Partners' Capital Account [Line Items]
Distribution declared	$ 2,449
Net income subsequent to the IPO in excess of distribution	215
Limited partners' interest in net income subsequent to IPO	$ 2,664
Weighted average units outsanding:
Basic and diluted	14,373,615
Net income per limited partner unit:
Income per limited partner unit	$ 0.19
Limited Partners' Subordinated Units [Member]
Limited Partners' Capital Account [Line Items]
Distribution declared	$ 2,162
Net income subsequent to the IPO in excess of distribution	189
Limited partners' interest in net income subsequent to IPO	$ 2,351
Weighted average units outsanding:
Basic and diluted	12,686,115
Net income per limited partner unit:
Income per limited partner unit	$ 0.19

Related Party Transactions (Sales to Related Parties) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Related Party Transaction [Line Items]
Net sales - Westlake	$ 289,601		$ 1,088,561
Predecessor [Member]
Related Party Transaction [Line Items]
Net sales - Westlake		$ 391,801		$ 1,195,870
Affiliated Entity [Member] \| Westlake [Member]
Related Party Transaction [Line Items]
Net sales - Westlake	$ 289,601		$ 1,088,561
Affiliated Entity [Member] \| Westlake [Member] \| Predecessor [Member]
Related Party Transaction [Line Items]
Net sales - Westlake		$ 391,801		$ 1,195,870

Related Party Transactions (Cost of Sales from Related Parties) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Related Party Transaction [Line Items]
Cost of sales	$ 227,015		$ 832,304
Predecessor [Member]
Related Party Transaction [Line Items]
Cost of sales		$ 327,152		$ 924,663
Affiliated Entity [Member] \| Westlake [Member]
Related Party Transaction [Line Items]
Feedstock purchased from Westlake and included in cost of sales	63,108		63,108
Other charges from Westlake and included in cost of sales	13,879		47,000
Cost of sales	$ 76,987		$ 110,108
Affiliated Entity [Member] \| Westlake [Member] \| Predecessor [Member]
Related Party Transaction [Line Items]
Feedstock purchased from Westlake and included in cost of sales		0		0
Other charges from Westlake and included in cost of sales		15,484		46,273
Cost of sales		$ 15,484		$ 46,273

Related Party Transactions (Services from Related Parties Included in SG&A Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Related Party Transaction [Line Items]
Services received from Westlake and included in selling, general and administrative expenses	$ 8,860		$ 22,803
Predecessor [Member]
Related Party Transaction [Line Items]
Services received from Westlake and included in selling, general and administrative expenses		$ 6,391		$ 19,326
Affiliated Entity [Member] \| Westlake [Member]
Related Party Transaction [Line Items]
Services received from Westlake and included in selling, general and administrative expenses	$ 4,283		$ 30,538
Affiliated Entity [Member] \| Westlake [Member] \| Predecessor [Member]
Related Party Transaction [Line Items]
Services received from Westlake and included in selling, general and administrative expenses		$ 4,845		$ 29,906

Related Party Transactions (Goods and Services from Related Parties that have been Capitalized) (Details) - Affiliated Entity [Member] - Westlake [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Related Party Transaction [Line Items]
Goods and services purchased from Westlake and capitalized as assets	$ 830		$ 2,074
Predecessor [Member]
Related Party Transaction [Line Items]
Goods and services purchased from Westlake and capitalized as assets		$ 624		$ 15,256

Related Party Transactions (Accounts Receivable from and Accounts Payable to Related Parties) (Details) - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Accounts receivable, net—Westlake	$ 28,500
Accounts payable—Westlake	(18,127)
Predecessor [Member]
Related Party Transaction [Line Items]
Accounts receivable, net—Westlake		$ 0
Accounts payable—Westlake		0
Affiliated Entity [Member] \| Westlake [Member]
Related Party Transaction [Line Items]
Accounts receivable, net—Westlake	28,500
Accounts payable—Westlake	$ (18,127)
Affiliated Entity [Member] \| Westlake [Member] \| Predecessor [Member]
Related Party Transaction [Line Items]
Accounts receivable, net—Westlake		0
Accounts payable—Westlake		$ 0

Related Party Transactions (Debt Payable to Related Parties) (Details) - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Long-term debt payable to Westlake	$ 188,523	$ 252,973
Affiliated Entity [Member] \| Westlake [Member]
Related Party Transaction [Line Items]
Long-term debt payable to Westlake	$ 188,523	$ 252,973

Related Party Transactions (General) (Details) - Westlake [Member] $ in Thousands	Sep. 30, 2014 USD ($)
Senior unsecured revolving credit facility [Member]
Related Party Transaction [Line Items]
Outstanding letters of credit	$ 32,399
Senior Notes [Member]
Related Party Transaction [Line Items]
Outstanding debt	754,000
Unamortized discount on senior notes	$ 921

Long-term debt payable to Westlake (Details) $ in Thousands	9 Months Ended	12 Months Ended
Long-term debt payable to Westlake (Details) $ in Thousands	Sep. 30, 2014 USD ($)	Dec. 31, 2013 USD ($) note
Related Party Transaction [Line Items]
Long-term debt	$ 188,523	$ 252,973
Limited Partner [Member]
Related Party Transaction [Line Items]
Number of intercompany promissory notes \| note		3
Senior Notes [Member] \| 2006 Pipeline Note [Member] \| Limited Partner [Member]
Related Party Transaction [Line Items]
Long-term debt	$ 0	$ 14,400
Senior Notes [Member] \| 2006 Pipeline Note [Member] \| Prime Rate [Member] \| Limited Partner [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent	0.25%
Senior Notes [Member] \| 2013 Promissory Note [Member] \| Limited Partner [Member]
Related Party Transaction [Line Items]
Long-term debt	$ 168,376	238,573
Senior Notes [Member] \| 2013 Promissory Note [Member] \| Prime Rate [Member] \| Limited Partner [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent	1.50%
Line of Credit [Member] \| Senior Unsecured Revolving Credit Facility [Member] \| Limited Partner [Member]
Related Party Transaction [Line Items]
Long-term debt	$ 20,147	$ 0
Line of Credit [Member] \| Senior Unsecured Revolving Credit Facility [Member] \| LIBOR [Member] \| Limited Partner [Member]
Related Party Transaction [Line Items]
Basis spread on variable rate, percent	3.00%

Derivative Instruments (Textual) (Detail)	Sep. 30, 2014 customer derivative
Open [Member]
Derivative [Line Items]
Number of derivatives \| derivative	0
Designated As Fair Value Hedges \| Commodity Forward Contracts [Member]
Derivative [Line Items]
Number of derivatives \| customer	0

Derivative Instruments (Fair Values of Derivative Instruments in Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2013
Accrued Liabilities
Derivatives, Fair Value [Line Items]
Total derivative liabilities	$ 0	$ 176
Accounts Receivable
Derivatives, Fair Value [Line Items]
Total derivative assets	0	296
Forward Contracts [Member] \| Accrued Liabilities
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Liabilities	0	176
Forward Contracts [Member] \| Accounts Receivable
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Assets	$ 0	$ 296

Derivative Instruments (Impact of Derivative Instruments on Income) (Details) - Cost of Sales - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Designated As Fair Value Hedges \| Firm Commitment Derivative Items Designated As Hedged Item
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	$ 0	$ 236	$ 0	$ 15
Designated As Fair Value Hedges \| Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	0	(232)	0	(342)
Derivatives Not Designated As Hedging Instruments \| Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	$ (8,873)	$ 4,854	$ (9,244)	$ 9,897

Fair Value Measurements (Summary of Assets and Liabilities Accounted at Fair Value on Recurring Basis) (Details) - Recurring [Member] - Forward Contracts [Member] $ in Thousands	Dec. 31, 2013 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk management assets - Commodity forward contracts	$ 296
Risk management liabilities - Commodity forward contracts	(176)
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk management assets - Commodity forward contracts	48
Risk management liabilities - Commodity forward contracts	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk management assets - Commodity forward contracts	248
Risk management liabilities - Commodity forward contracts	$ (176)

Fair Value Measurements (Summary of Carrying and Fair Values of Long Term Debt) (Details) - Senior Notes [Member] - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2013
2006 Pipeline Note [Member] \| Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	$ 0	$ 14,400
2006 Pipeline Note [Member] \| Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	0	13,922
2013 Promissory Note [Member] \| Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	168,376	238,573
2013 Promissory Note [Member] \| Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	168,376	238,573
Senior unsecured revolving credit facility [Member] \| Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	20,147	0
Senior unsecured revolving credit facility [Member] \| Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	$ 20,147	$ 0

Income Taxes (Detail)	7 Months Ended	9 Months Ended
Income Taxes (Detail)	Aug. 03, 2014	Sep. 30, 2013
Income Tax Disclosure [Abstract]
Effective income tax rate	35.40%	35.50%
U.S. federal statutory income tax rate	35.00%	35.00%

Supplemental Information (Details) - USD ($)	3 Months Ended		9 Months Ended
Supplemental Information (Details) - USD ($)	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Related Party Transaction [Line Items]
Reduction in capital expenditure accrual			$ 8,564,000	$ 9,512,000
Westlake [Member] \| Affiliated Entity [Member]
Related Party Transaction [Line Items]
Interest incurred, added to principal on promissory notes outstanding	$ 2,089,000	$ 2,168,000	$ 9,530,000	4,498,000
Related party notes payable deemed settled through net investment				238,600,000
Cash transferred in related party notes payable settlement				$ 0

Supplemental Information (Liabilities Retained by Westlake) (Details) $ in Thousands	Sep. 30, 2014 USD ($)
Accounts receivable, net—third parties	$ 29,606
Inventories	5,551
Prepaid expenses and other current assets	303
Deferred income taxes	0
Property, plant and equipment, net	806,648
Equity investments	0
Accounts payable - third parties	(12,827)
Accrued liabilities	(3,999)
Deferred income taxes	(1,507)
Westlake [Member]
Accounts receivable, net—third parties	64,650
Inventories	85,057
Prepaid expenses and other current assets	669
Deferred income taxes	4,448
Property, plant and equipment, net	62,886
Equity investments	9,338
Accounts payable - third parties	(101,671)
Accrued liabilities	(37,451)
Deferred income taxes	(189,615)
Long-term debt payable to Westlake	(137,103)
Other liabilities	(914)
Total	$ (239,706)

Major Customer and Concentration Risk (Details)	3 Months Ended		9 Months Ended
Major Customer and Concentration Risk (Details)	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net sales [Member] \| Customer Concentration Risk [Member] \| Westlake [Member] \| Affiliated Entity [Member]
Concentration Risk [Line Items]
Concentration risk percentage	73.90%	72.50%	73.70%	76.40%

Commitments and Contingencies (Details)	1 Months Ended
Commitments and Contingencies (Details)	Dec. 31, 2007
Damage from Fire, Explosion or Other Hazard [Member] \| Settled Litigation [Member] \| Goodrich and PolyOne [Member] \| Polyone [Member]
Loss Contingencies [Line Items]
Percentage of responsibility assumed	100.00%

Subsequent Events (Details) - Subsequent Event [Member] $ / shares in Units, $ in Thousands	Oct. 28, 2014 USD ($) $ / shares
Subsequent Event [Line Items]
Distribution declared per unit \| $ / shares	$ 0.1704
Distribution declared \| $	$ 4,611

Label	Element	Value
Partners' Capital, Predecessor Net Liabilities Not Assumed By Subsidiary	wlkp_PartnersCapitalPredecessorNetLiabilitiesNotAssumedBySubsidiary	$ 239,706,000
Partners' Capital Account, Distributions	us-gaap_PartnersCapitalAccountDistributions	448,101,000
Predecessor [Member]
Partners' Capital, Predecessor Net Liabilities Not Assumed By Subsidiary	wlkp_PartnersCapitalPredecessorNetLiabilitiesNotAssumedBySubsidiary	239,706,000
Partners' Capital Account, Distributions	us-gaap_PartnersCapitalAccountDistributions	448,101,000
Partners' Capital Allocation Of Net Investment To Unitholders	wlkp_PartnersCapitalAllocationOfNetInvestmentToUnitholders	(608,371,000)
Noncontrolling Interest [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	49,542,000
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance	242,572,000
Partners' Capital Allocation Of Net Investment To Unitholders	wlkp_PartnersCapitalAllocationOfNetInvestmentToUnitholders	573,329,000
Unidentified Third Parties [Member] \| Common Units [Member] \| Limited Partner [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	2,399,000
Partners' Capital Account, Public Sale of Units	us-gaap_PartnersCapitalAccountPublicSaleOfUnits	286,088,000
Parent Company And Subsidiaries, Excluding Reporting Entity And Subsidiaries [Member] \| General Partner [Member]
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance	(242,572,000)
Parent Company And Subsidiaries, Excluding Reporting Entity And Subsidiaries [Member] \| Common Units [Member] \| Limited Partner [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	265,000
Partners' Capital Allocation Of Net Investment To Unitholders	wlkp_PartnersCapitalAllocationOfNetInvestmentToUnitholders	3,563,000
Parent Company And Subsidiaries, Excluding Reporting Entity And Subsidiaries [Member] \| Subordinated Units [Member] \| Limited Partner [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	2,351,000
Partners' Capital Allocation Of Net Investment To Unitholders	wlkp_PartnersCapitalAllocationOfNetInvestmentToUnitholders	$ 31,479,000