2.2.0.7 false Condensed Consolidated Statements of Operations (USD $) 0020 - Statement - Condensed Consolidated Statements of Operations true false In Thousands, except Per Share data false false 1 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 2 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 3 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 4 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ 5 Revenue: 3 us-gaap_RevenuesAbstract us-gaap true na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 6 Revenue 4 us-gaap_GasGatheringTransportationMarketingAndProcessingRevenue us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 true true false false 276948000 276948 false false false 2 true true false false 185000000 185000 false false false 3 true true false false 592563000 592563 false false false 4 true true false false 368367000 368367 false false false xbrli:monetaryItemType monetary Revenue related to midstream and downstream gas activities. May include the following: gathering from wells, processing to remove impurities, storage, transmission, and the sale of natural gas and related products. No authoritative reference available. false 7 Derivative gain (loss) 4 mwe_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToRevenue mwe false credit duration Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk... false false false false false false false false false false false terselabel false 1 false true false false 46902000 46902 false false false 2 false true false false -83235000 -83235 false false false 3 false true false false 39666000 39666 false false false 4 false true false false -74931000 -74931 false false false xbrli:monetaryItemType monetary Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk derivatives not designated as hedging instruments. Revenue gains and losses relate to contracts utilized to economically hedge the cash flow for the sale of a product. No authoritative reference available. false 8 Total revenue 4 us-gaap_Revenues us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 323850000 323850 false false false 2 false true false false 101765000 101765 false false false 3 false true false false 632229000 632229 false false false 4 false true false false 293436000 293436 false false false xbrli:monetaryItemType monetary Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 true 9 Operating expenses: 3 us-gaap_CostsAndExpensesAbstract us-gaap true na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 10 Purchased product costs 4 us-gaap_NaturalGasMidstreamCosts us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 128123000 128123 false false false 2 false true false false 80652000 80652 false false false 3 false true false false 272419000 272419 false false false 4 false true false false 182966000 182966 false false false xbrli:monetaryItemType monetary Cost of residue gas, natural gas liquids and condensate. Midstream is a term sometimes used to those industry activities that fall between exploration and production (upstream) and refining and marketing (downstream). The term is most often applied to pipeline transportation of crude oil and natural gas. No authoritative reference available. false 11 Derivative (gain) loss related to purchased product costs 4 mwe_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToProductCost mwe false credit duration Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk... false false false false false false false false false false true negated false 1 false true false false -8392000 -8392 false false false 2 false true false false 2625000 2625 false false false 3 false true false false 4997000 4997 false false false 4 false true false false 32138000 32138 false false false xbrli:monetaryItemType monetary Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk derivatives not designated as hedging instruments. Purchased product costs gains and losses relate to contracts utilized to economically hedge costs. No authoritative reference available. false 12 Facility expenses 4 us-gaap_FacilityCosts us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 37427000 37427 false false false 2 false true false false 32336000 32336 false false false 3 false true false false 75332000 75332 false false false 4 false true false false 63780000 63780 false false false xbrli:monetaryItemType monetary Facility expenses incurred related to gas and oil produced and sold during the reporting period. No authoritative reference available. false 13 Derivative loss (gain) related to facility expenses 4 mwe_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToFacilityExpense mwe false credit duration Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk... false false false false false false false false false false true negated false 1 false true false false 934000 934 false false false 2 false true false false -854000 -854 false false false 3 false true false false 128000 128 false false false 4 false true false false -1225000 -1225 false false false xbrli:monetaryItemType monetary Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk derivatives not designated as hedging instruments. Facility expense gains and losses relate to contracts utilized to economically hedge electricity costs for a facility. No authoritative reference available. false 14 Selling, general and administrative expenses 4 us-gaap_SellingGeneralAndAdministrativeExpense us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 16419000 16419 false false false 2 false true false false 14861000 14861 false false false 3 false true false false 37927000 37927 false false false 4 false true false false 30788000 30788 false false false xbrli:monetaryItemType monetary The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 4 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 4 -Paragraph 5A false 15 Depreciation 4 us-gaap_Depreciation us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 29818000 29818 false false false 2 false true false false 23414000 23414 false false false 3 false true false false 58005000 58005 false false false 4 false true false false 44357000 44357 false false false xbrli:monetaryItemType monetary The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 false 16 Amortization of intangible assets 4 us-gaap_AmortizationOfIntangibleAssets us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 10193000 10193 false false false 2 false true false false 10212000 10212 false false false 3 false true false false 20386000 20386 false false false 4 false true false false 20445000 20445 false false false xbrli:monetaryItemType monetary The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by (used in) operations using the indirect method. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 45 -Subparagraph a(2) false 17 Loss on disposal of property, plant and equipment 4 us-gaap_GainLossOnDispositionOfAssets us-gaap true credit duration No definition available. false false false false false false false false false false true negated false 1 false true false false 188000 188 false false false 2 false true false false 70000 70 false false false 3 false true false false 179000 179 false false false 4 false true false false 799000 799 false false false xbrli:monetaryItemType monetary The gains and losses included in earnings resulting from the sale or disposal of tangible assets. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 144 -Paragraph 47 false 18 Accretion of asset retirement obligations 4 us-gaap_AssetRetirementObligationAccretionExpense us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 69000 69 false false false 2 false true false false 44000 44 false false false 3 false true false false 212000 212 false false false 4 false true false false 91000 91 false false false xbrli:monetaryItemType monetary Amount of accretion expense recognized in the income statement during the period that is associated with asset retirement obligations. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. Such accretion expense representing changes in the liability for an asset retirement obligation due to passage of time is the result of applying an interest method of allocation to the amount of the liability at the beginning of the period. The interest rate used to measure that change shall be the credit-adjusted risk-free rate that existed when the liability, or portion thereof, was initially measured. That amount shall be recognized as an increase in the carrying amount of the liability and as an expense classified as an operating item in the statement of income. Accretion expense shall not be considered to be interest cost for purposes of capitalization of interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 143 -Paragraph 13, 14 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 143 -Paragraph 22 -Subparagraph c(3) false 19 Impairment of long-lived assets 4 us-gaap_AssetImpairmentCharges us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false true false false 5855000 5855 false false false 3 false false false false 0 0 false false false 4 false true false false 5855000 5855 false false false xbrli:monetaryItemType monetary The charge against earnings resulting from the aggregate write down of all assets from their carrying value to their fair value. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 144 -Paragraph 45, 46, 47 false 20 Total operating expenses 4 us-gaap_CostsAndExpenses us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 214779000 214779 false false false 2 false true false false 169215000 169215 false false false 3 false true false false 469585000 469585 false false false 4 false true false false 379994000 379994 false false false xbrli:monetaryItemType monetary Total costs of sales and operating expenses for the period. No authoritative reference available. true 21 Income (loss) from operations 3 us-gaap_OperatingIncomeLoss us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 109071000 109071 false false false 2 false true false false -67450000 -67450 false false false 3 false true false false 162644000 162644 false false false 4 false true false false -86558000 -86558 false false false xbrli:monetaryItemType monetary The net result for the period of deducting operating expenses from operating revenues. No authoritative reference available. true 22 Other income (expense): 3 us-gaap_NonoperatingIncomeExpenseAbstract us-gaap true na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 23 Earnings from unconsolidated affiliates 4 us-gaap_IncomeLossFromEquityMethodInvestments us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 1585000 1585 false false false 2 false true false false 1196000 1196 false false false 3 false true false false 1517000 1517 false false false 4 false true false false 1091000 1091 false false false xbrli:monetaryItemType monetary This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. Such amount typically reflects adjustments similar to those made in preparing consolidated statements, including adjustments to eliminate intercompany gains and losses, and to amortize, if appropriate, any difference between cost and underlying equity in net assets of the investee at the date of investment. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 19 -Subparagraph c Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 11 -Article 7 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 6 -Subparagraph b false 24 Interest income 4 us-gaap_InvestmentIncomeInterest us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 377000 377 false false false 2 false true false false 60000 60 false false false 3 false true false false 763000 763 false false false 4 false true false false 101000 101 false false false xbrli:monetaryItemType monetary Income derived from investments in debt securities and on cash and cash equivalents the earnings of which reflect the time value of money or transactions in which the payments are for the use or forbearance of money. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Article 5 false 25 Interest expense 4 us-gaap_InterestExpense us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -25755000 -25755 false false false 2 false true false false -22742000 -22742 false false false 3 false true false false -49537000 -49537 false false false 4 false true false false -40524000 -40524 false false false xbrli:monetaryItemType monetary The cost of borrowed funds accounted for as interest that was charged against earnings during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 34 -Paragraph 21 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher OTS -Name Federal Regulation (FR) -Number Title 12 -Chapter V -Section 563c.102 -Paragraph 9 -Subsection II Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 9 -Article 9 false 26 Amortization of deferred financing costs and discount (a component of interest expense) 4 us-gaap_AmortizationOfFinancingCostsAndDiscounts us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -2280000 -2280 false false false 2 false true false false -2046000 -2046 false false false 3 false true false false -4892000 -4892 false false false 4 false true false false -3437000 -3437 false false false xbrli:monetaryItemType monetary The component of interest expense representing the noncash expenses charged against earnings in the period to allocate debt discount and premium, and the costs to issue debt and obtain financing over the related debt instruments. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 false 27 Derivative gain related to interest expense 4 mwe_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToInterestExpense mwe false credit duration Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk... false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 1871000 1871 false false false 4 false false false false 0 0 false false false xbrli:monetaryItemType monetary Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk derivatives not designated as hedging instruments. Interest expense gains and losses relate to changes in the fair value of interest rate swaps. No authoritative reference available. false 28 Miscellaneous (expense) income, net 4 us-gaap_OtherNonoperatingIncomeExpense us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false -9000 -9 false false false 2 false true false false 2383000 2383 false false false 3 false true false false 1053000 1053 false false false 4 false true false false 1721000 1721 false false false xbrli:monetaryItemType monetary The net amount of other nonoperating income and expense, which does not qualify for separate disclosure on the income statement under materiality guidelines. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 false 29 Income (loss) before provision for income tax 3 mwe_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest mwe false credit duration Sum of operating profit and nonoperating income (expense) before, income taxes, extraordinary items, cumulative effects of... false false false false false false false false false false false totallabel false 1 false true false false 82989000 82989 false false false 2 false true false false -88599000 -88599 false false false 3 false true false false 113419000 113419 false false false 4 false true false false -127606000 -127606 false false false xbrli:monetaryItemType monetary Sum of operating profit and nonoperating income (expense) before, income taxes, extraordinary items, cumulative effects of changes in accounting principles, and noncontrolling interest. No authoritative reference available. true 30 Provision for income tax expense (benefit): 3 us-gaap_IncomeTaxExpenseBenefitAbstract us-gaap true na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 31 Current 4 us-gaap_CurrentIncomeTaxExpenseBenefit us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 923000 923 false false false 2 false true false false 323000 323 false false false 3 false true false false 6721000 6721 false false false 4 false true false false 6576000 6576 false false false xbrli:monetaryItemType monetary The component of income tax expense for the period representing amounts of income taxes paid or payable (or refundable) for the period for all income tax obligations as determined by applying the provisions of relevant enacted tax laws to relevant amounts of taxable income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 289 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 45 -Subparagraph a false 32 Deferred 4 us-gaap_DeferredIncomeTaxExpenseBenefit us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 15098000 15098 false false false 2 false true false false -19726000 -19726 false false false 3 false true false false 13726000 13726 false false false 4 false true false false -35317000 -35317 false false false xbrli:monetaryItemType monetary The component of income tax expense for the period representing the net change in the entity's deferred tax assets and liabilities pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 45 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 289 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 false 33 Total provision for income tax 4 us-gaap_IncomeTaxExpenseBenefit us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 16021000 16021 false false false 2 false true false false -19403000 -19403 false false false 3 false true false false 20447000 20447 false false false 4 false true false false -28741000 -28741 false false false xbrli:monetaryItemType monetary The sum of the current income tax expense (benefit) and the deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 45 -Subparagraph a, b true 34 Net income (loss) 3 us-gaap_ProfitLoss us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 66968000 66968 false false false 2 false true false false -69196000 -69196 false false false 3 false true false false 92972000 92972 false false false 4 false true false false -98865000 -98865 false false false xbrli:monetaryItemType monetary The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 5 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) true 35 Net (income) loss attributable to non-controlling interest 3 us-gaap_NetIncomeLossAttributableToNoncontrollingInterest us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -6751000 -6751 false false false 2 false true false false 1690000 1690 false false false 3 false true false false -11245000 -11245 false false false 4 false true false false 1710000 1710 false false false xbrli:monetaryItemType monetary The portion of net income (loss) attributable to the noncontrolling interest (if any) deducted in order to derive the portion attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 false 36 Net income (loss) attributable to the Partnership 3 us-gaap_NetIncomeLossAllocatedToLimitedPartners us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 true true false false 60217000 60217 false false false 2 true true false false -67506000 -67506 false false false 3 true true false false 81727000 81727 false false false 4 true true false false -97155000 -97155 false false false xbrli:monetaryItemType monetary Aggregate amount of net income allocated to general partners in a publicly trade limited partnership or master limited partnership (MLP). Limited partners have limited liability and do not manage the partnership. No authoritative reference available. true 37 Net income (loss) attributable to the Partnership's common unitholders per common unit (Note 12): 3 us-gaap_EarningsPerUnitAbstract us-gaap true na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 38 Basic (in dollars per unit) 4 us-gaap_NetIncomeLossPerOutstandingLimitedPartnershipUnit us-gaap true na duration No definition available. false false false false false false false false false false false terselabel true 1 true true false false 0.84 0.84 false false false 2 true true false false -1.18 -1.18 false false false 3 true true false false 1.18 1.18 false false false 4 true true false false -1.71 -1.71 false false false us-types:perUnitItemType decimal Net income (loss) allocated to each outstanding limited partnership unit in a publicly traded limited partnership or master limited partnership (MLP). Limited partners have limited liability and do not manage the partnership. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 4 -Section F false 39 Diluted (in dollars per unit) 4 us-gaap_NetIncomeLossPerOutstandingLimitedPartnershipUnitDiluted us-gaap true na duration No definition available. false false false false false false false false false false false terselabel true 1 true true false false 0.84 0.84 false false false 2 true true false false -1.18 -1.18 false false false 3 true true false false 1.18 1.18 false false false 4 true true false false -1.71 -1.71 false false false us-types:perUnitItemType decimal Net income (loss) allocated to each limited partner unit outstanding during the reporting period and each unit that would have been outstanding assuming the issuance of limited partner units for all dilutive potential units outstanding during the reporting period. Limited partners have limited liability and do not manage the partnership. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 4 -Section F false 40 Weighted average number of outstanding common units: 3 mwe_WeightedAverageNumberOfOutstandingCommonUnitsAbstract mwe false na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 41 Basic (in units) 4 us-gaap_WeightedAverageLimitedPartnershipUnitsOutstanding us-gaap true na duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 71111000 71111 false false false 2 false true false false 57603000 57603 false false false 3 false true false false 68795000 68795 false false false 4 false true false false 57207000 57207 false false false xbrli:sharesItemType shares Weighted average number of limited partnership units outstanding determined by relating the portion of time within a reporting period that limited partnership units have been outstanding to the total time in that period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 4 -Section F false 42 Diluted (in units) 4 us-gaap_WeightedAverageLimitedPartnershipUnitsOutstandingDiluted us-gaap true na duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 71298000 71298 false false false 2 false true false false 57603000 57603 false false false 3 false true false false 68889000 68889 false false false 4 false true false false 57207000 57207 false false false xbrli:sharesItemType shares Weighted average number of limited partnership units outstanding determined by relating the portion of time within a reporting period that limited partnership units have been outstanding to the total time in that period. Used in the calculation of diluted net income (loss) per limited partnership unit. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 4 -Section F false 43 Cash distribution declared per common unit (in dollars per unit) 3 us-gaap_DistributionsPerLimitedPartnershipUnitOutstanding us-gaap true na duration No definition available. false false false false false false false false false false false terselabel true 1 true true false false 0.64 0.64 false false false 2 true true false false 0.64 0.64 false false false 3 true true false false 1.28 1.28 false false false 4 true true false false 1.28 1.28 false false false us-types:perShareItemType decimal Cash dividends declared or paid to each outstanding limited partnership unit of a publicly traded limited partnership or master limited partnership (MLP) during the reporting period. Limited partners have limited liability and do not manage the partnership. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 4 -Section F false 4 39 false Thousands Thousands NoRounding false true