Risks and Uncertainties [Abstract] Concentration Risk [Table] Concentration Risk [Table] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Net sales [Member] Sales Revenue, Net [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Customer Concentration Risk [Member] Customer Concentration Risk [Member] Customer [Axis] Customer [Axis] Customer [Domain] Customer [Domain] Westlake [Member] Parent Company And Subsidiaries, Excluding Reporting Entity And Subsidiaries [Member] Parent Company and Subsidiaries, Excluding Reporting Entity and Subsidiaries [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Affiliated Entity [Member] Affiliated Entity [Member] Concentration Risk [Line Items] Concentration Risk [Line Items] Concentration risk percentage Concentration Risk, Percentage Property, Plant and Equipment [Abstract] Property, plant and equipment Property, Plant and Equipment, Net Depreciation expense on property, plant and equipment Depreciation Commitments and Contingencies Disclosure [Abstract] Loss Contingencies [Table] Loss Contingencies [Table] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Damage from Fire, Explosion or Other Hazard [Member] Damage from Fire, Explosion or Other Hazard [Member] Litigation Status [Axis] Litigation Status [Axis] Litigation Status [Domain] Litigation Status [Domain] Settled Litigation [Member] Settled Litigation [Member] Agreement reached between parties in a litigation that occurs without judicial intervention, supervision or approval. Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] Goodrich and PolyOne [Member] Goodrich and PolyOne [Member] Goodrich and PolyOne [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Polyone [Member] Polyone [Member] PolyOne [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Percentage of responsibility assumed Loss Contingencies, Percentage Of Responsibility Assumed Loss Contingencies, Percentage Of Responsibility Assumed Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Other Assets [Abstract] Statement [Table] Statement [Table] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Assets [Member] Other Assets [Member] Statement [Line Items] Statement [Line Items] Amortization expense Amortization Other Assets Investments and Other Noncurrent Assets [Text Block] Document Documentand Entity Information [Abstract] Document - Document and Entity Information [Abstract] Document Information [Table] Document Information [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Common units [Member] Common Units [Member] Common Units [Member] Subordinated units [Member] Subordinated Units [Member] Subordinated Units [Member] Document Information [Line Items] Document Information [Line Items] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Related Party Transactions [Abstract] Long-term debt payable to Westlake Related Party Transactions, Long-term Debt [Text Block] Related Party Transactions, Long-term Debt [Text Block] Investments, Debt and Equity Securities [Abstract] Recent Accounting Pronouncements New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Schedule of Related Party Transactions Schedule of Related Party Transactions [Table Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Related Party Transactions Related Party Transactions Disclosure [Text Block] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Predecessor [Member] Predecessor [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Feedstock purchased from Westlake and included in cost of sales Related Parties Amount In Cost Of Sales, Feedstock Purchased Related Parties Amount In Cost Of Sales, Feedstock Purchased Other charges from Westlake and included in cost of sales Cost Of Goods Sold, Other Cost Of Goods Sold, Other Cost of sales Cost of Goods Sold Organization, Consolidation and Presentation of Financial Statements [Abstract] Interest incurred, added to principal on promissory notes outstanding Interest Incurred, Added to Debt Outstanding Interest Incurred, Added to Debt Outstanding Reduction in capital expenditure accrual Increase (Decrease) in Capital Expenditure Accrual Increase (Decrease) in Capital Expenditure Accrual Related party notes payable deemed settled through net investment Increase (Decrease) in Notes Payable, Related Parties Cash transferred in related party notes payable settlement Cash Transferred In Notes Payable Settlement, Related Parties Cash Transferred In Notes Payable Settlement, Related Parties Accounts receivable, net—Westlake Accounts Receivable, Related Parties, Current Accounts payable—Westlake Accounts Payable, Related Parties, Current Property, Plant and Equipment Property, Plant and Equipment Disclosure [Text Block] Equity [Abstract] Schedule of Limited Partners' Capital Account by Class [Table] Schedule of Limited Partners' Capital Account by Class [Table] Westlake Chemical OpCo LP [Member] Westlake Chemical OpCo LP [Member] Westlake Chemical OpCo LP [Member] Westlake Chemical OpCo GP LLC [Member] Westlake Chemical OpCo GP LLC [Member] Westlake Chemical OpCo GP LLC [Member] Partner Type [Axis] Partner Type [Axis] Partner Type of Partners' Capital Account, Name [Domain] Partner Type of Partners' Capital Account, Name [Domain] Westlake [Member] Limited Partner [Member] Limited Partners' Capital Account by Class [Axis] Limited Partners' Capital Account by Class [Axis] Limited Partners' Capital Account, Class [Domain] Limited Partners' Capital Account, Class [Domain] OpCo and OpCo's General Partner Interest [Member] Partnership Interest [Member] Subsidiary, Sale of Stock [Axis] Subsidiary, Sale of Stock [Axis] Sale of Stock, Name of Transaction [Domain] Sale of Stock, Name of Transaction [Domain] Over-Allotment Option [Member] Over-Allotment Option [Member] Over-Allotment Option [Member] IPO [Member] IPO [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Loans Payable [Member] Loans Payable [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 2013 Promissory Note [Member] Promissory Notes, 2013 [Member] Promissory Notes, 2013 [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Preformation Capital Expenditure [Member] Preformation Capital Expenditure [Member] Preformation Capital Expenditure [Member] Cash Reserve Turnaround [Member] Cash Reserve Turnaround [Member] Cash Reserve Turnaround [Member] Intercompany Debt [Member] Intercompany Debt [Member] Intercompany Debt [Member] Ethylene Sales Agreement [Member] Ethylene Sales Agreement [Member] Ethylene Sales Agreement [Member] Excess Production Option [Member] Excess Production Option [Member] Excess Production Option [Member] Feedstock Supply Agreement [Member] Feedstock Supply Agreement [Member] Feedstock Supply Agreement [Member] Services And Secondment Agreement [Member] Services And Secondment Agreement [Member] Services And Secondment Agreement [Member] Site Lease Agreement [Member] Site Lease Agreement [Member] Site Lease Agreement [Member] Investee [Member] Investee [Member] Limited Liability Company [Member] Limited Liability Company [Member] Investor [Member] Investor [Member] Majority-Owned Subsidiary, Unconsolidated [Member] Majority-Owned Subsidiary, Unconsolidated [Member] Limited Partners' Capital Account [Line Items] Limited Partners' Capital Account [Line Items] Partnership's ownership interest Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest Debt assumed by acquiree Intercompany Debt Intercompany Debt Number of units sold in public offering Partners' Capital Account, Units, Sold in Public Offering Price per unit Sale of Unit, Price Per Unit Sale of Unit, Price Per Unit Price per unit, net of underwriting discount Sale of Unit, Price Per Unit, Net of Underwriting Discount Sale of Unit, Price Per Unit, Net of Underwriting Discount Units outstanding Limited Partners' Capital Account, Units Outstanding Net proceeds from issuance of common units Proceeds from Issuance of Common Limited Partners Units Payments of unit issuance costs Payments of Unit Issuance Costs Payments of Unit Issuance Costs Additional ownership interest acquired Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Additional Ownership Interest Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Additional Ownership Interest Carrying value of additional partnership interest purchased Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Excess cash paid over carrying value of partnership interest Noncontrolling Interest, Decrease Due To Excess Cash Paid Over Carrying Value Noncontrolling Interest, Decrease Due To Excess Cash Paid Over Carrying Value Capital expenditures Pre-formation Capital Expenditures Pre-formation Capital Expenditures Use of proceeds from public offering Subsidiary Initial Public Offering, Use Of Proceeds Subsidiary Initial Public Offering, Use Of Proceeds Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract] Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract] Term of sales agreement Long-term Purchase Commitment, Period Period covered by the long-term purchase commitment, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Minimum percentage required to be purchased Long-term Purchase Commitment, Minimum Percentage Required Long-term Purchase Commitment, Minimum Percentage Required Maximum mass required to be purchased Long-term Purchase Commitment, Maximum Volume Required Long-term Purchase Commitment, Maximum Volume Required Percentage of excess production that can be purchased Long-term Purchase Commitment, Option To Purchase Excess Production, Percentage Long-term Purchase Commitment, Option To Purchase Excess Production, Percentage Number of years used to calculate average expenses Long-term Purchase Commitment, Terms of Fee, Number Of Years Used To Calculate Average Expenses Long-term Purchase Commitment, Terms of Fee, Number Of Years Used To Calculate Average Expenses Purchase commitment, fixed margin on variable pricing Long-term Purchase Commitment, Fixed Margin Long-term Purchase Commitment, Fixed Margin Purchase commitment, renewal term Long-term Purchase Commitment, Renewal Term Long-term Purchase Commitment, Renewal Term Related partiy transactions, term of agreements Related Party Transaction, Term Of Agreement Related Party Transaction, Term Of Agreement Related Party Transaction, Counterparty Default, Period Of Default, Allowing Termination Of Agreement Related Party Transaction, Counterparty Default, Period Of Default, Allowing Termination Of Agreement Related Party Transaction, Counterparty Default, Period Of Default, Allowing Termination Of Agreement Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Major Customer and Concentration of Credit Risk Concentration Risk Disclosure [Text Block] Income Statement [Abstract] Public [Member] Unidentified Third Parties [Member] Unidentified Third Parties [Member] Net sales - Westlake Revenue from Related Parties Net co-product, ethylene and feedstock sales—third parties Other Revenue, Net Net sales Revenue, Net Gross profit Gross Profit Services received from Westlake and included in selling, general and administrative expenses Selling, General and Administrative Expense Income from operations Operating Income (Loss) Other income (expense) Nonoperating Income (Expense) [Abstract] Interest expense—Westlake Interest Expense, Related Party Other income, net Nonoperating Income (Expense) Income before income taxes Income (Loss) from Continuing Operations before Income Taxes Income (Loss) from continuing operations, including the portion attributable to noncontrolling interest, and income (loss) from equity method investments, but before extraordinary items, cumulative effects of changes in accounting principles and income taxes. Provision for income taxes Income Tax Expense (Benefit) Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Less: Net income attributable to noncontrolling interest in OpCo Net Income (Loss) Attributable to Noncontrolling Interest Limited partners' interest in net income subsequent to IPO Net Income (Loss) Attributable to Parent Net income attributable to Westlake Chemical Partners LP subsequent to initial public offering per limited partner unit (basic and diluted) Earnings Per Share, Basic and Diluted [Abstract] Income per limited partner unit Earnings Per Share, Basic and Diluted Weighted average limited partner units outstanding (basic and diluted) Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract] Weighted average limited partner units outstanding Weighted Average Number of Shares Outstanding, Basic and Diluted Earnings Per Share [Abstract] Distribution declared Distributed Earnings Net income subsequent to the IPO in excess of distribution Undistributed Earnings, Basic Statement of Financial Position [Abstract] Limited Partner [Member] General Partner [Member] General Partner [Member] ASSETS Assets [Abstract] Current assets Assets, Current [Abstract] Cash and cash equivalents Cash Equivalents, at Carrying Value Accounts receivable, net—third parties Receivables, Net, Current Inventories Inventory, Net Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Deferred income taxes Deferred Tax Assets, Net of Valuation Allowance, Current Total current assets Assets, Current Property, plant and equipment, net Equity investments Equity Method Investments Other assets, net Intangible assets, net Intangible Assets, Net (Including Goodwill) Deferred charges and other assets Deferred Costs and Other Assets Total other assets, net Other Assets, Noncurrent Total assets Assets LIABILITIES AND NET INVESTMENT Liabilities and Equity [Abstract] Current liabilities Liabilities, Current [Abstract] Accounts payable—Westlake Accounts payable—third parties Accounts Payable, Current Accrued liabilities Accrued Liabilities, Current Total current liabilities Liabilities, Current Long-term debt payable to Westlake Due to Related Parties, Noncurrent Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Other liabilities Other Liabilities, Noncurrent Total liabilities Liabilities Commitments and contingencies (Notes 10 and 16) Commitments and Contingencies NET INVESTMENT Stockholders' Equity Attributable to Parent [Abstract] Net investment Net Investment In Partnership Net Investment In Partnership Limited Partners' Capital Account Limited Partners' Capital Account General Partners' Capital Account General Partners' Capital Account Partners' capital Partners' Capital Noncontrolling interest in OpCo Noncontrolling Interest in Limited Partnerships Total equity Partners' Capital, Including Portion Attributable to Noncontrolling Interest Total liabilities and equity Liabilities and Equity Senior Notes [Member] Senior Notes [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Senior unsecured revolving credit facility [Member] Revolving Credit Facility [Member] Outstanding letters of credit Letters of Credit Outstanding, Amount Outstanding debt Long-term Debt Unamortized discount on senior notes Debt Instrument, Unamortized Discount Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Derivative Instrument Risk [Axis] Derivative Instrument [Axis] Derivative Contract Type [Domain] Derivative Contract [Domain] Forward Contracts [Member] Forward Contracts [Member] Accrued Liabilities Accrued Liabilities [Member] Accounts Receivable Accounts Receivable [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Not designated as hedging instruments, Derivative Assets Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value Total derivative assets Derivative Asset, Fair Value, Gross Asset Not designated as hedging instruments, Derivative Liabilities Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value Total derivative liabilities Derivative Liability, Fair Value, Gross Liability Accounts payable - third parties Accrued liabilities Deferred income taxes Long-term debt payable to Westlake Long-term Debt, Excluding Current Maturities Other liabilities Other Liabilities Total Assets, Net Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Statement of Partners' Capital [Abstract] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Noncontrolling Interest in OpCo [Member] Noncontrolling Interest [Member] Equity, beginning balance Contribution of debt payable to Westlake into net investment Partners' Capital Account, Contributions Net income for the period Net distributions to Westlake Partners' Capital Account, Distributions Predecessor net liabilities not assumed by OpCo Partners' Capital, Predecessor Net Liabilities Not Assumed By Subsidiary Partners' Capital, Predecessor Net Liabilities Not Assumed By Subsidiary Allocation of net investment to unitholders Partners' Capital Allocation Of Net Investment To Unitholders Partners' Capital Allocation Of Net Investment To Unitholders Proceeds from initial public offering, net of finance and other offering costs Partners' Capital Account, Public Sale of Units Distribution to the noncontrolling interest in OpCo Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Purchase of additional interest in OpCo Noncontrolling Interest, Increase from Subsidiary Equity Issuance Equity, ending balance Accounts Receivable, Net [Abstract] Schedule Of Accounts Receivable Schedule Of Accounts And Financing Receivables [Table Text Block] Tabular disclosure of the various categories of receivables, including trade and other receivables, and for each the gross carrying value, allowance (if appropriate), and net carrying value as of the balance sheet date. Derivative [Table] Derivative [Table] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Designated As Fair Value Hedges Designated as Hedging Instrument [Member] Commodity Forward Contracts [Member] Commodity Forward Contracts [Member] Commodity forward contracts [Member] Position [Axis] Position [Axis] Position [Domain] Position [Domain] Open [Member] Open [Member] Open [Member] Derivative [Line Items] Derivative [Line Items] Number of derivatives Derivative, Number of Instruments Held Summary Of Assets And Liabilities Accounted At Fair Value On A Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Summary Of Carrying And Fair Values Of Long-Term Debt Fair Value, by Balance Sheet Grouping [Table Text Block] Statement of Cash Flows [Abstract] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Provision for (recovery of) doubtful accounts Provision for (Recovery of) Doubtful Accounts Amount of the current period expense charged against operations for the purpose of reducing receivables, including notes receivable, to an amount that approximates their net realizable value (i.e. provision for). Conversely, may also be the amount of doubtful accounts recovered during the current period (i.e. recovery of). Loss from disposition of fixed assets Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Deferred income taxes Deferred Income Tax Expense (Benefit) Equity in income of joint venture, net of dividends Income (Loss) from Equity Method Investments, Net of Dividends or Distributions Changes in operating assets and liabilities Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts and Other Receivables Increase (Decrease) in Accounts Receivable, Related Parties Increase (Decrease) in Accounts Receivable, Related Parties Inventories Increase (Decrease) in Inventories Prepaid expenses and other current assets Increase Decrease In Prepaid Expenses And Other Current Assets The increase (decrease) during the reporting period in the aggregate value of prepaid expenses and other current assets. Accounts payable Increase (Decrease) in Accounts Payable Accrued liabilities Increase (Decrease) in Accrued Liabilities Other, net Increase (Decrease) in Other Operating Assets and Liabilities, Net Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Additions to property, plant and equipment Payments to Acquire Property, Plant, and Equipment Settlements of derivative instruments Payments for (Proceeds from) Derivative Instrument, Investing Activities Net cash used for investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds from debt payable to Westlake Proceeds from Related Party Debt Repayment of debt payable to Westlake with proceeds from the initial public offering Repayments of Related Party Debt Proceeds from initial public offering distributed to Westlake Payments of Capital Distribution Net distributions to Westlake prior to initial public offering Payments of Distributions to Affiliates Net cash used for financing activities Net Cash Provided by (Used in) Financing Activities Net increase in cash Cash and Cash Equivalents, Period Increase (Decrease) Cash at beginning of period Cash and Cash Equivalents, at Carrying Value Cash at end of period Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Trade customers Accounts Receivable, Gross, Current Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current Receivables from trade customers and affiliates, net Trade Customer And Affiliate Receivable Net Current The aggregate of amounts due from customers or clients, within one year of the balance sheet date (or one operating cycle, if longer), for goods or services that have been delivered or sold in the normal course of business, and amounts due from related parties (affiliates) payable within one year of the balance sheet, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection. Other Other Receivables Current Amount due from other third-parties, or arising from transactions not separately disclosed, within one year of the balance sheet date (or the normal operating cycle, whichever is longer). Accounts receivable, net Basis of Financial Statements Basis of Accounting, Policy [Policy Text Block] Inventory Disclosure [Abstract] Inventory, Current [Table] Inventory, Current [Table] Inventory [Line Items] Inventory [Line Items] Finished products Inventory, Finished Goods, Gross Feedstock, additives and chemicals Inventory, Work in Process and Raw Materials Materials and supplies Inventory Supplies Aggregated amount of supplies that will be consumed. Inventories Supplemental Information Additional Financial Information Disclosure [Text Block] Schedule of Earnings Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Units issued Limited Partners' Capital Account, Units Issued Net Income Per Limited Partner Unit Earnings Per Share [Text Block] Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Distribution declared per unit Distribution Made to Limited Partner, Distributions Declared, Per Unit Distribution declared Distribution Made to Limited Partner, Cash Distributions Declared Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Limited Partners' Common Units [Member] Limited Partners' Subordinated Units [Member] Weighted average units outsanding: Basic and diluted Net income per limited partner unit: Inventories Inventory Disclosure [Text Block] Limited partner interest Number of ethylene production facilities Number of Production Facilities Number of Production Facilities Percentage of production expected to sell to Westlake Long-term Purchase Commitment, Expected Percentage Of Production To Be Sold Long-term Purchase Commitment, Expected Percentage Of Production To Be Sold Number of reportable segments Number of Reportable Segments Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Recurring [Member] Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Risk management assets - Commodity forward contracts Risk management liabilities - Commodity forward contracts Initial Public Offering Stockholders' Equity Note Disclosure [Text Block] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent U.S. federal statutory income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Goods and services purchased from Westlake and capitalized as assets Related Party Transaction, Purchases from Related Party Schedule Of Inventory Schedule of Inventory, Current [Table Text Block] Fair Values of Derivatives Instruments in Consolidated Balance Sheets Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Impact of Derivatives Instruments Designated as Fair Value Hedges Schedule of Derivatives Instruments Statements of Financial Performance and Financial Position, Location [Table Text Block] Impact of Derivative Instruments Not Designated as Fair Value Hedges Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block] Line of Credit [Member] Line of Credit [Member] 2006 Pipeline Note [Member] Pipeline Note, 2006 [Member] Pipeline Note, 2006 [Member] Senior Unsecured Revolving Credit Facility [Member] Senior Unsecured Revolving Credit Facility [Member] Senior Unsecured Revolving Credit Facility [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] Prime Rate [Member] Prime Rate [Member] LIBOR [Member] London Interbank Offered Rate (LIBOR) [Member] Long-term debt Basis spread on variable rate, percent Debt Instrument, Basis Spread on Variable Rate Number of intercompany promissory notes Number of Intercompany Promissory Notes Number of Intercompany Promissory Notes Schedule of Liabilities Retained By Parent Company [Table Text Block] Schedule of Liabilities Retained By Parent Company [Table Text Block] Schedule of Liabilities Retained By Parent Company [Table Text Block] Business and Basis of Presentation Business Description and Basis of Presentation [Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping, Disclosure Item Amounts [Axis] Measurement Basis [Axis] Fair Value, Disclosure Item Amounts [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Carrying Value [Member] Reported Value Measurement [Member] Fair Value [Member] Estimate of Fair Value Measurement [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Senior Notes Senior Notes, Fair Value Disclosure This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents senior notes as of the balance sheet date. Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk [Table] Derivative Instruments, Gain (Loss) [Table] Derivatives Not Designated As Hedging Instruments Not Designated as Hedging Instrument [Member] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Cost of Sales Cost of Sales [Member] Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Firm Commitment Derivative Items Designated As Hedged Item Firm Commitment Derivative Items Designated As Hedged Item [Member] Firm Commitment Derivative Items Designated as Hedged Item [Member] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Gain (Loss) Recognized in Income on Derivative Derivative, Gain (Loss) on Derivative, Net Accounts Receivable Loans, Notes, Trade and Other Receivables Disclosure [Text Block]