2.4.0.84151 - Disclosure - Segment Information (Details 2)truefalsefalse1false USDfalsefalse$D2013Q2http://www.sec.gov/CIK0001166036duration2013-04-01T00:00:002013-06-30T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$2false USDfalsefalse$D2012Q2http://www.sec.gov/CIK0001166036duration2012-04-01T00:00:002012-06-30T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$3false USDfalsefalse$D2013Q2YTDhttp://www.sec.gov/CIK0001166036duration2013-01-01T00:00:002013-06-30T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$4false USDfalsefalse$D2012Q2YTDhttp://www.sec.gov/CIK0001166036duration2012-01-01T00:00:002012-06-30T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1true 3us-gaap_SegmentReportingInformationLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Segment information2false 4us-gaap_GasGatheringTransportationMarketingAndProcessingRevenueus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse395421000395421000USD$falsetruefalse2truefalsefalse306755000306755000USD$falsetruefalse3truefalsefalse768879000768879000USD$falsetruefalse4truefalsefalse702733000702733000USD$falsetruefalsexbrli:monetaryItemTypemonetaryRevenue related to midstream and downstream gas activities. May include the following: gathering from wells, processing to remove impurities, storage, transmission, and the sale of natural gas and related products.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 23 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62136-109447 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62246-109447 false2Revenue3false 4mwe_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToRevenuemwe_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse1969900019699000USD$falsefalsefalse2truefalsefalse136067000136067000USD$falsefalsefalse3truefalsefalse1951400019514000USD$falsefalsefalse4truefalsefalse8735200087352000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk derivatives not designated as hedging instruments. Revenue gains and losses relate to contracts utilized to economically hedge the cash flow for the sale of a product.No definition available.false2Derivative gain not allocated to segments4false 4mwe_DeferredRevenueAdjustmentmwe_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse14370001437000USD$falsefalsefalse2truefalsefalse13240001324000USD$falsefalsefalse3truefalsefalse28010002801000USD$falsefalsefalse4truefalsefalse32170003217000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe difference between the revenue recognized on the consolidated financial statements and the recognized for segment purposes. Certain contracts in which more consideration is received in the initial years than in later years and GAAP requires the entity to recognize the revenue evenly over the term of the contract by deferring revenue in the initial years. The chief operating decision maker evaluates segment performance and makes decisions based on the actual consideration received and therefore the segment revenues do not reflect the revenue deferral.No definition available.false2Revenue deferral adjustment and other5false 4us-gaap_Revenuesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse415120000415120000USD$falsefalsefalse2truefalsefalse442822000442822000USD$falsefalsefalse3truefalsefalse788393000788393000USD$falsefalsefalse4truefalsefalse790085000790085000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 true2Total revenue6false 4us-gaap_SellingGeneralAndAdministrativeExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-25499000-25499000USD$falsefalsefalse2truefalsefalse-21700000-21700000USD$falsefalsefalse3truefalsefalse-50741000-50741000USD$falsefalsefalse4truefalsefalse-46748000-46748000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 4 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -SubTopic 10 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6386349&loc=d3e3636-108311 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Paragraph 5A -Chapter 4 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Selling, general and administrative expenses7false 4us-gaap_Depreciationus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-71562000-71562000USD$falsefalsefalse2truefalsefalse-41336000-41336000USD$falsefalsefalse3truefalsefalse-139579000-139579000USD$falsefalsefalse4truefalsefalse-80918000-80918000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 false2Depreciation8false 4us-gaap_AmortizationOfIntangibleAssetsus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-17092000-17092000USD$falsefalsefalse2truefalsefalse-12307000-12307000USD$falsefalsefalse3truefalsefalse-31922000-31922000USD$falsefalsefalse4truefalsefalse-23292000-23292000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=7658586&loc=d3e16323-109275 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 45 -Subparagraph a(2) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Amortization of intangible assets9false 4us-gaap_GainLossOnDispositionOfAssetsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse3773600037736000USD$falsefalsefalse2truefalsefalse-1342000-1342000USD$falsefalsefalse3truefalsefalse3759800037598000USD$falsefalsefalse4truefalsefalse-2328000-2328000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe gains (losses) included in earnings resulting from the sale or disposal of tangible assets. This item does not include any gain (loss) recognized on the sale of oil and gas property or timber property.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2941-110230 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 144 -Paragraph 47 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Gain (loss) on disposal of property, plant and equipment10false 4us-gaap_AssetRetirementObligationAccretionExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-157000-157000USD$falsefalsefalse2truefalsefalse-160000-160000USD$falsefalsefalse3truefalsefalse-509000-509000USD$falsefalsefalse4truefalsefalse-396000-396000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 143 -Paragraph 22 -Subparagraph c(3) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 143 -Paragraph 13, 14 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Accretion of asset retirement obligations11false 4us-gaap_OperatingIncomeLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse140022000140022000USD$falsefalsefalse2truefalsefalse257741000257741000USD$falsefalsefalse3truefalsefalse203685000203685000USD$falsefalsefalse4truefalsefalse308233000308233000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net result for the period of deducting operating expenses from operating revenues.No definition available.true2Income from operations12false 4us-gaap_IncomeLossFromEquityMethodInvestmentsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse430000430000USD$falsefalsefalse2truefalsefalse11090001109000USD$falsefalsefalse3truefalsefalse665000665000USD$falsefalsefalse4truefalsefalse15480001548000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis 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. 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Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 6 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 19 -Subparagraph c -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.12) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 11 -Article 7 false2Earnings from unconsolidated affiliate13false 4us-gaap_InvestmentIncomeInterestus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse6200062000USD$falsefalsefalse2truefalsefalse159000159000USD$falsefalsefalse3truefalsefalse211000211000USD$falsefalsefalse4truefalsefalse231000231000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryIncome derived from investments in debt securities and on cash and cash equivalents the earnings of which reflect the time value of money or transactions in which the payments are for the use or forbearance of money.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(b)) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 false2Interest income14false 4us-gaap_InterestExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-36955000-36955000USD$falsefalsefalse2truefalsefalse-26762000-26762000USD$falsefalsefalse3truefalsefalse-75291000-75291000USD$falsefalsefalse4truefalsefalse-56234000-56234000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cost of borrowed funds accounted for as interest that was charged against earnings during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 34 -Paragraph 21 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.9) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 9 -Article 9 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher OTS -Name Federal Regulation (FR) -Number Title 12 -Section 563c.102 -Paragraph 9 -Chapter V -Subsection II -LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy. false2Interest expense15false 4us-gaap_AmortizationOfFinancingCostsAndDiscountsus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-1784000-1784000USD$falsefalsefalse2truefalsefalse-1245000-1245000USD$falsefalsefalse3truefalsefalse-3614000-3614000USD$falsefalsefalse4truefalsefalse-2515000-2515000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of noncash expense included in interest expense to allocate debt discount and premium, and the costs to issue debt and obtain financing over the related debt instruments. Alternate captions include noncash interest expense.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Amortization of deferred financing costs and discount (a component of interest expense)16false 4us-gaap_GainsLossesOnExtinguishmentOfDebtus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse-38455000-38455000USD$falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryDifference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 50 -Section 40 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12317-112629 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 50 -Section 40 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12355-112629 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 26 -Paragraph 20, 21 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Loss on redemption of debt17false 4us-gaap_OtherNonoperatingIncomeExpenseus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse60006000USD$falsefalsefalse2truefalsefalse40004000USD$falsefalsefalse3truefalsefalse60006000USD$falsefalsefalse4truefalsefalse6200062000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 false2Miscellaneous income, net18false 4us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterestus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse101781000101781000USD$falsefalsefalse2truefalsefalse231006000231006000USD$falsefalsefalse3truefalsefalse8720700087207000USD$falsefalsefalse4truefalsefalse251325000251325000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 10 -Article 5 true2Income before provision for income tax19false 4mwe_ManagementFeeRevenuesmwe_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse200000200000USD$falsefalsefalse2truefalsefalse400000400000USD$falsefalsefalse3truefalsefalse600000600000USD$falsefalsefalse4truefalsefalse800000800000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents revenues from management fees.No definition available.false2Management fee revenues unconsolidated affiliate20false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5false USDtruefalse$D2013Q2_ReportableSegmentsMemberhttp://www.sec.gov/CIK0001166036duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseTotal reportable segmentsus-gaap_StatementGeographicalAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_ReportableSegmentsMemberus-gaap_StatementGeographicalAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Total reportable segments21true 3us-gaap_SegmentReportingInformationLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Segment information22false 4us-gaap_GasGatheringTransportationMarketingAndProcessingRevenueus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse396858000396858000USD$falsefalsefalse2truefalsefalse308079000308079000USD$falsefalsefalse3truefalsefalse771680000771680000USD$falsefalsefalse4truefalsefalse705950000705950000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRevenue 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.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 23 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62136-109447 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62246-109447 false2Revenue23false 4mwe_MinorityInterestInOperatingIncomeLossLimitedPartnershipsmwe_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-1090000-1090000USD$falsefalsefalse2truefalsefalse-85000-85000USD$falsefalsefalse3truefalsefalse-2365000-2365000USD$falsefalsefalse4truefalsefalse-82000-82000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of operating income or loss attributable to the reportable segments for the period that is attributable to the non-controlling partners of the entity's less than wholly-owned subsidiaries.No definition available.false2Portion of operating income (loss) attributable to non-controlling interests24false 4us-gaap_OperatingIncomeLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse177472000177472000USD$falsefalsefalse2truefalsefalse144698000144698000USD$falsefalsefalse3truefalsefalse339200000339200000USD$falsefalsefalse4truefalsefalse337448000337448000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net result for the period of deducting operating expenses from operating revenues.No definition available.true2Income from operations25false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse9false USDtruefalse$D2013Q2_SouthwestMemberhttp://www.sec.gov/CIK0001166036duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseSouthwest Segmentus-gaap_StatementGeographicalAxisxbrldihttp://xbrl.org/2006/xbrldimwe_SouthwestMemberus-gaap_StatementGeographicalAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Southwest Segment26true 3us-gaap_SegmentReportingInformationLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Segment information27false 4us-gaap_GasGatheringTransportationMarketingAndProcessingRevenueus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse227842000227842000USD$falsefalsefalse2truefalsefalse206551000206551000USD$falsefalsefalse3truefalsefalse436208000436208000USD$falsefalsefalse4truefalsefalse441927000441927000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRevenue 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.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 23 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62136-109447 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62246-109447 false2Revenue28false 4mwe_DeferredRevenueAdjustmentmwe_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse200000200000USD$falsefalsefalse2truefalsefalse200000200000USD$falsefalsefalse3truefalsefalse400000400000USD$falsefalsefalse4truefalsefalse400000400000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe difference between the revenue recognized on the consolidated financial statements and the recognized for segment purposes. Certain contracts in which more consideration is received in the initial years than in later years and GAAP requires the entity to recognize the revenue evenly over the term of the contract by deferring revenue in the initial years. The chief operating decision maker evaluates segment performance and makes decisions based on the actual consideration received and therefore the segment revenues do not reflect the revenue deferral.No definition available.false2Revenue deferral adjustment and other29false 4mwe_MinorityInterestInOperatingIncomeLossLimitedPartnershipsmwe_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse5300053000USD$falsefalsefalse2truefalsefalse2800028000USD$falsefalsefalse3truefalsefalse117000117000USD$falsefalsefalse4truefalsefalse3100031000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of operating income or loss attributable to the reportable segments for the period that is attributable to the non-controlling partners of the entity's less than wholly-owned subsidiaries.No definition available.false2Portion of operating income (loss) attributable to non-controlling interests30false 4us-gaap_OperatingIncomeLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse7477100074771000USD$falsefalsefalse2truefalsefalse8257500082575000USD$falsefalsefalse3truefalsefalse140281000140281000USD$falsefalsefalse4truefalsefalse181777000181777000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net result for the period of deducting operating expenses from operating revenues.No definition available.true2Income from operations31false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse13false USDtruefalse$D2013Q2_NortheastMemberhttp://www.sec.gov/CIK0001166036duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseNortheast Segmentus-gaap_StatementGeographicalAxisxbrldihttp://xbrl.org/2006/xbrldimwe_NortheastMemberus-gaap_StatementGeographicalAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Northeast Segment32true 3us-gaap_SegmentReportingInformationLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Segment information33false 4us-gaap_GasGatheringTransportationMarketingAndProcessingRevenueus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse4536500045365000USD$falsefalsefalse2truefalsefalse4205100042051000USD$falsefalsefalse3truefalsefalse102701000102701000USD$falsefalsefalse4truefalsefalse128969000128969000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRevenue 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.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 23 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62136-109447 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62246-109447 false2Revenue34false 4mwe_DeferredRevenueAdjustmentmwe_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse14000001400000USD$falsefalsefalse2truefalsefalse15000001500000USD$falsefalsefalse3truefalsefalse30000003000000USD$falsefalsefalse4truefalsefalse36000003600000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe difference between the revenue recognized on the consolidated financial statements and the recognized for segment purposes. Certain contracts in which more consideration is received in the initial years than in later years and GAAP requires the entity to recognize the revenue evenly over the term of the contract by deferring revenue in the initial years. The chief operating decision maker evaluates segment performance and makes decisions based on the actual consideration received and therefore the segment revenues do not reflect the revenue deferral.No definition available.false2Revenue deferral adjustment and other35false 4us-gaap_OperatingIncomeLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse2358400023584000USD$falsefalsefalse2truefalsefalse2419800024198000USD$falsefalsefalse3truefalsefalse5473400054734000USD$falsefalsefalse4truefalsefalse7905100079051000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net result for the period of deducting operating expenses from operating revenues.No definition available.true2Income from operations36false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse17false USDtruefalse$D2013Q2_UnallocatedAmountToSegmentMemberhttp://www.sec.gov/CIK0001166036duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseUnallocated Segmentus-gaap_StatementGeographicalAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_UnallocatedAmountToSegmentMemberus-gaap_StatementGeographicalAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Unallocated Segment37true 3us-gaap_SegmentReportingInformationLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Segment information38false 4mwe_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToRevenuemwe_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse3933100039331000USD$falsefalsefalse2truefalsefalse188792000188792000USD$falsefalsefalse3truefalsefalse5018200050182000USD$falsefalsefalse4truefalsefalse123023000123023000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount 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 definition available.false2Derivative gain not allocated to segments39false 4mwe_DeferredRevenueAdjustmentmwe_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse14370001437000USD$falsefalsefalse2truefalsefalse13240001324000USD$falsefalsefalse3truefalsefalse28010002801000USD$falsefalsefalse4truefalsefalse32170003217000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe difference between the revenue recognized on the consolidated financial statements and the recognized for segment purposes. Certain contracts in which more consideration is received in the initial years than in later years and GAAP requires the entity to recognize the revenue evenly over the term of the contract by deferring revenue in the initial years. The chief operating decision maker evaluates segment performance and makes decisions based on the actual consideration received and therefore the segment revenues do not reflect the revenue deferral.No definition available.false2Revenue deferral adjustment and other40false 4mwe_FacilityCostsLaborAndRelatedExpensemwe_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-368000-368000USD$falsefalsefalse2truefalsefalse-183000-183000USD$falsefalsefalse3truefalsefalse-754000-754000USD$falsefalsefalse4truefalsefalse-633000-633000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate amount of expenditures for compensation included in facility costs related to gas and oil produced and sold during the reporting period that is not allocated to any operating segment.No definition available.false2Compensation expense included in facility expenses not allocated to segments41false 4mwe_FacilityExpensesAdjustmentsmwe_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse26880002688000USD$falsetruefalse2truefalsefalse26880002688000USD$falsetruefalse3truefalsefalse53760005376000USD$falsetruefalse4truefalsefalse53760005376000USD$falsetruefalsexbrli:monetaryItemTypemonetaryThis element represents the facility expense adjustments to reconcile segment facility expenses to consolidated facility expenses.No definition available.false2Facility expenses adjustmentsfalseSegment Information (Details 2) (USD $)NoRoundingUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.markwest.com/role/DisclosureSegmentInformationDetails2441