2.4.0.6 Html 207 274 1 false 55 0 false 11 false false R1.htm 0000 - Document - Document and Entity Information Sheet http://www.markwest.com/role/DocumentAndEntityInformation Document and Entity Information true false R2.htm 0010 - Statement - Condensed Consolidated Balance Sheets Sheet http://www.markwest.com/role/BalanceSheet Condensed Consolidated Balance Sheets false false R3.htm 0015 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) Sheet http://www.markwest.com/role/BalanceSheetParenthetical Condensed Consolidated Balance Sheets (Parenthetical) false false R4.htm 0020 - Statement - Condensed Consolidated Statements of Operations Sheet http://www.markwest.com/role/StatementOfIncome Condensed Consolidated Statements of Operations false false R5.htm 0030 - Statement - Condensed Consolidated Statements of Changes in Equity Sheet http://www.markwest.com/role/StatementOfStockholdersEquity Condensed Consolidated Statements of Changes in Equity false false R6.htm 0040 - Statement - Condensed Consolidated Statements of Cash Flows Sheet http://www.markwest.com/role/CashFlows Condensed Consolidated Statements of Cash Flows false false R7.htm 1010 - Disclosure - Organization and Basis of Presentation Sheet http://www.markwest.com/role/DisclosureOrganizationAndBasisOfPresentation Organization and Basis of Presentation false false R8.htm 1020 - Disclosure - Recent Accounting Pronouncements Sheet http://www.markwest.com/role/DisclosureRecentAccountingPronouncements Recent Accounting Pronouncements false false R9.htm 1030 - Disclosure - Variable Interest Entities Sheet http://www.markwest.com/role/DisclosureVariableInterestEntities Variable Interest Entities false false R10.htm 1040 - Disclosure - Derivative Financial Instruments Sheet http://www.markwest.com/role/DisclosureDerivativeFinancialInstruments Derivative Financial Instruments false false R11.htm 1050 - Disclosure - Fair Value Sheet http://www.markwest.com/role/DisclosureFairValue Fair Value false false R12.htm 1060 - Disclosure - Inventories Sheet http://www.markwest.com/role/DisclosureInventories Inventories false false R13.htm 1070 - Disclosure - Long-Term Debt Sheet http://www.markwest.com/role/DisclosureLongTermDebt Long-Term Debt false false R14.htm 1080 - Disclosure - Equity Sheet http://www.markwest.com/role/DisclosureEquity Equity false false R15.htm 1090 - Disclosure - Commitments and Contingencies Sheet http://www.markwest.com/role/DisclosureCommitmentsAndContingencies Commitments and Contingencies false false R16.htm 1100 - Disclosure - Income Taxes Sheet http://www.markwest.com/role/DisclosureIncomeTaxes Income Taxes false false R17.htm 1110 - Disclosure - Earnings (Loss) Per Common Unit Sheet http://www.markwest.com/role/DisclosureEarningsLossPerCommonUnit Earnings (Loss) Per Common Unit false false R18.htm 1120 - Disclosure - Segment Information Sheet http://www.markwest.com/role/DisclosureSegmentInformation Segment Information false false R19.htm 1130 - Disclosure - Supplemental Condensed Consolidating Financial Information Sheet http://www.markwest.com/role/DisclosureSupplementalCondensedConsolidatingFinancialInformation Supplemental Condensed Consolidating Financial Information false false R20.htm 1140 - Disclosure - Supplemental Cash Flow Information Sheet http://www.markwest.com/role/DisclosureSupplementalCashFlowInformation Supplemental Cash Flow Information false false R21.htm 3030 - Disclosure - Variable Interest Entities (Tables) Sheet http://www.markwest.com/role/DisclosureVariableInterestEntitiesTables Variable Interest Entities (Tables) false false R22.htm 3040 - Disclosure - Derivative Financial Instruments (Tables) Sheet http://www.markwest.com/role/DisclosureDerivativeFinancialInstrumentsTables Derivative Financial Instruments (Tables) false false R23.htm 3050 - Disclosure - Fair Value (Tables) Sheet http://www.markwest.com/role/DisclosureFairValueTables Fair Value (Tables) false false R24.htm 3060 - Disclosure - Inventories (Tables) Sheet http://www.markwest.com/role/DisclosureInventoriesTables Inventories (Tables) false false R25.htm 3070 - Disclosure - Long-Term Debt (Tables) Sheet http://www.markwest.com/role/DisclosureLongTermDebtTables Long-Term Debt (Tables) false false R26.htm 3080 - Disclosure - Equity (Tables) Sheet http://www.markwest.com/role/DisclosureEquityTables Equity (Tables) false false R27.htm 3100 - Disclosure - Income Taxes (Tables) Sheet http://www.markwest.com/role/DisclosureIncomeTaxesTables Income Taxes (Tables) false false R28.htm 3110 - Disclosure - Earnings (Loss) Per Common Unit (Tables) Sheet http://www.markwest.com/role/DisclosureEarningsLossPerCommonUnitTables Earnings (Loss) Per Common Unit (Tables) false false R29.htm 3120 - Disclosure - Segment Information (Tables) Sheet http://www.markwest.com/role/DisclosureSegmentInformationTables Segment Information (Tables) false false R30.htm 3130 - Disclosure - Supplemental Condensed Consolidating Financial Information (Tables) Sheet http://www.markwest.com/role/DisclosureSupplementalCondensedConsolidatingFinancialInformationTables Supplemental Condensed Consolidating Financial Information (Tables) false false R31.htm 3140 - Disclosure - Supplemental Cash Flow Information (Tables) Sheet http://www.markwest.com/role/DisclosureSupplementalCashFlowInformationTables Supplemental Cash Flow Information (Tables) false false R32.htm 4030 - Disclosure - Variable Interest Entities (Details) Sheet http://www.markwest.com/role/DisclosureVariableInterestEntitiesDetails Variable Interest Entities (Details) false false R33.htm 4040 - Disclosure - Derivative Financial Instruments (Details) Sheet http://www.markwest.com/role/DisclosureDerivativeFinancialInstrumentsDetails Derivative Financial Instruments (Details) false false R34.htm 4041 - Disclosure - Derivative Financial Instruments (Details 2) Sheet http://www.markwest.com/role/DisclosureDerivativeFinancialInstrumentsDetails2 Derivative Financial Instruments (Details 2) false false R35.htm 4050 - Disclosure - Fair Value (Details) Sheet http://www.markwest.com/role/DisclosureFairValueDetails Fair Value (Details) false false R36.htm 4051 - Disclosure - Fair Value (Details 2) Sheet http://www.markwest.com/role/DisclosureFairValueDetails2 Fair Value (Details 2) false false R37.htm 4052 - Disclosure - Fair Value (Details 3) Sheet http://www.markwest.com/role/DisclosureFairValueDetails3 Fair Value (Details 3) false false R38.htm 4053 - Disclosure - Fair Value (Details 4) Sheet http://www.markwest.com/role/DisclosureFairValueDetails4 Fair Value (Details 4) false false R39.htm 4060 - Disclosure - Inventories (Details) Sheet http://www.markwest.com/role/DisclosureInventoriesDetails Inventories (Details) false false R40.htm 4070 - Disclosure - Long-Term Debt (Details) Sheet http://www.markwest.com/role/DisclosureLongTermDebtDetails Long-Term Debt (Details) false false R41.htm 4080 - Disclosure - Equity (Details) Sheet http://www.markwest.com/role/DisclosureEquityDetails Equity (Details) false false R42.htm 4100 - Disclosure - Income Taxes (Details) Sheet http://www.markwest.com/role/DisclosureIncomeTaxesDetails Income Taxes (Details) false false R43.htm 4110 - Disclosure - Earnings (Loss) Per Common Unit (Details) Sheet http://www.markwest.com/role/DisclosureEarningsLossPerCommonUnitDetails Earnings (Loss) Per Common Unit (Details) false false R44.htm 4120 - Disclosure - Segment Information (Details) Sheet http://www.markwest.com/role/DisclosureSegmentInformationDetails Segment Information (Details) false false R45.htm 4121 - Disclosure - Segment Information (Details 2) Sheet http://www.markwest.com/role/DisclosureSegmentInformationDetails2 Segment Information (Details 2) false false R46.htm 4122 - Disclosure - Segment Information (Details 3) Sheet http://www.markwest.com/role/DisclosureSegmentInformationDetails3 Segment Information (Details 3) false false R47.htm 4130 - Disclosure - Supplemental Condensed Consolidating Financial Information (Details) Sheet http://www.markwest.com/role/DisclosureSupplementalCondensedConsolidatingFinancialInformationDetails Supplemental Condensed Consolidating Financial Information (Details) false false R48.htm 4131 - Disclosure - Supplemental Condensed Consolidating Financial Information (Details 2) Sheet http://www.markwest.com/role/DisclosureSupplementalCondensedConsolidatingFinancialInformationDetails2 Supplemental Condensed Consolidating Financial Information (Details 2) false false R49.htm 4132 - Disclosure - Supplemental Condensed Consolidating Financial Information (Details 3) Sheet http://www.markwest.com/role/DisclosureSupplementalCondensedConsolidatingFinancialInformationDetails3 Supplemental Condensed Consolidating Financial Information (Details 3) false false R50.htm 4140 - Disclosure - Supplemental Cash Flow Information (Details) Sheet http://www.markwest.com/role/DisclosureSupplementalCashFlowInformationDetails Supplemental Cash Flow Information (Details) false false All Reports Book All Reports Element mwe_DeferredRevenueAdjustment had a mix of decimals attribute values: -5 -3. Element mwe_PaymentsOfPremiumsOnRedemptionOfLongTermDebt had a mix of decimals attribute values: -5 -3. Element us-gaap_DebtInstrumentInterestRateStatedPercentage had a mix of decimals attribute values: 3 4. Element us-gaap_ExtinguishmentOfDebtAmount had a mix of decimals attribute values: -6 -5. Element us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering had a mix of decimals attribute values: -5 -3. 'Monetary' elements on report '4030 - Disclosure - Variable Interest Entities (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '4040 - Disclosure - Derivative Financial Instruments (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '4070 - Disclosure - Long-Term Debt (Details)' had a mix of different decimal attribute values. 'Monetary' elements on report '4080 - Disclosure - Equity (Details)' had a mix of different decimal attribute values. Process Flow-Through: 0010 - Statement - Condensed Consolidated Balance Sheets Process Flow-Through: Removing column 'Mar. 31, 2012' Process Flow-Through: Removing column 'Dec. 31, 2011' Process Flow-Through: 0015 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) Process Flow-Through: Removing column 'Mar. 31, 2012' Process Flow-Through: Removing column 'Dec. 31, 2011' Process Flow-Through: 0020 - Statement - Condensed Consolidated Statements of Operations Process Flow-Through: 0040 - Statement - Condensed Consolidated Statements of Cash Flows mwe-20130331.xml mwe-20130331.xsd mwe-20130331_cal.xml mwe-20130331_def.xml mwe-20130331_lab.xml mwe-20130331_pre.xml true true