2.2.0.25 true Sheet 0010 - Statement - CONSOLIDATED BALANCE SHEETS CONSOLIDATED BALANCE SHEETS http://www.markwest.com/role/BalanceSheet false R1.xml false Sheet 0015 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical) CONSOLIDATED BALANCE SHEETS (Parenthetical) http://www.markwest.com/role/BalanceSheetParenthetical false R2.xml false Sheet 0020 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS CONSOLIDATED STATEMENTS OF OPERATIONS http://www.markwest.com/role/StatementOfIncome false R3.xml false Sheet 0030 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY AND COMPREHENSIVE INCOME CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY AND COMPREHENSIVE INCOME http://www.markwest.com/role/StatementOfChangesInEquity false R4.xml false Sheet 0035 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY AND COMPREHENSIVE INCOME (Parenthetical) CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY AND COMPREHENSIVE INCOME (Parenthetical) http://www.markwest.com/role/StatementOfChangesInEquityParenthetical false R5.xml false Sheet 0040 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS CONSOLIDATED STATEMENTS OF CASH FLOWS http://www.markwest.com/role/CashFlows false R6.xml false Sheet 1010 - Disclosure - Organization Organization http://www.markwest.com/role/DisclosureOrganization false R7.xml false Sheet 1020 - Disclosure - Summary of Significant Accounting Policies Summary of Significant Accounting Policies http://www.markwest.com/role/DisclosureSummaryOfSignificantAccountingPolicies false R8.xml false Sheet 1030 - Disclosure - Redemption and Merger Redemption and Merger http://www.markwest.com/role/DisclosureRedemptionAndMerger false R9.xml false Sheet 1040 - Disclosure - Variable Interest Entities Variable Interest Entities http://www.markwest.com/role/DisclosureVariableInterestEntities false R10.xml false Sheet 1050 - Disclosure - Divestitures Divestitures http://www.markwest.com/role/DisclosureDivestitures false R11.xml false Sheet 1060 - Disclosure - Derivative Financial Instruments Derivative Financial Instruments http://www.markwest.com/role/DisclosureDerivativeFinancialInstruments false R12.xml false Sheet 1070 - Disclosure - Fair Value Fair Value http://www.markwest.com/role/DisclosureFairValue false R13.xml false Sheet 1080 - Disclosure - Significant Customers and Concentration of Credit Risk Significant Customers and Concentration of Credit Risk http://www.markwest.com/role/DisclosureSignificantCustomersAndConcentrationOfCreditRisk false R14.xml false Sheet 1090 - Disclosure - Receivables Receivables http://www.markwest.com/role/DisclosureReceivables false R15.xml false Sheet 1100 - Disclosure - Inventories Inventories http://www.markwest.com/role/DisclosureInventories false R16.xml false Sheet 1110 - Disclosure - Property, Plant and Equipment Property, Plant and Equipment http://www.markwest.com/role/DisclosurePropertyPlantAndEquipment false R17.xml false Sheet 1120 - Disclosure - Goodwill and Intangible Assets Goodwill and Intangible Assets http://www.markwest.com/role/DisclosureGoodwillAndIntangibleAssets false R18.xml false Sheet 1130 - Disclosure - Impairment of Goodwill and Long-Lived Assets Impairment of Goodwill and Long-Lived Assets http://www.markwest.com/role/DisclosureImpairmentOfGoodwillAndLongLivedAssets false R19.xml false Sheet 1140 - Disclosure - Investment in Unconsolidated Affiliates Investment in Unconsolidated Affiliates http://www.markwest.com/role/DisclosureInvestmentInUnconsolidatedAffiliates false R20.xml false Sheet 1150 - Disclosure - Accrued Liabilities and Other Long-Term Liabilities Accrued Liabilities and Other Long-Term Liabilities http://www.markwest.com/role/DisclosureAccruedLiabilitiesAndOtherLongTermLiabilities false R21.xml false Sheet 1160 - Disclosure - Asset Retirement Obligation Asset Retirement Obligation http://www.markwest.com/role/DisclosureAssetRetirementObligation false R22.xml false Sheet 1170 - Disclosure - Long-Term Debt Long-Term Debt http://www.markwest.com/role/DisclosureLongTermDebt false R23.xml false Sheet 1180 - Disclosure - Equity Equity http://www.markwest.com/role/DisclosureEquity false R24.xml false Sheet 1190 - Disclosure - Commitments and Contingencies Commitments and Contingencies http://www.markwest.com/role/DisclosureCommitmentsAndContingencies false R25.xml false Sheet 1200 - Disclosure - Lease Operations Lease Operations http://www.markwest.com/role/DisclosureLeaseOperations false R26.xml false Sheet 1210 - Disclosure - Incentive Compensation Plans Incentive Compensation Plans http://www.markwest.com/role/DisclosureIncentiveCompensationPlans false R27.xml false Sheet 1220 - Disclosure - Employee Benefit Plan Employee Benefit Plan http://www.markwest.com/role/DisclosureEmployeeBenefitPlan false R28.xml false Sheet 1230 - Disclosure - Income Tax Income Tax http://www.markwest.com/role/DisclosureIncomeTax false R29.xml false Sheet 1240 - Disclosure - (Loss) Earnings Per Common Unit (Loss) Earnings Per Common Unit http://www.markwest.com/role/DisclosureLossEarningsPerCommonUnit false R30.xml false Sheet 1250 - Disclosure - Segment Information Segment Information http://www.markwest.com/role/DisclosureSegmentInformation false R31.xml false Sheet 1260 - Disclosure - Supplemental Condensed Consolidating Financial Information Supplemental Condensed Consolidating Financial Information http://www.markwest.com/role/DisclosureSupplementalCondensedConsolidatingFinancialInformation false R32.xml false Sheet 1270 - Disclosure - Supplemental Cash Flow Information Supplemental Cash Flow Information http://www.markwest.com/role/DisclosureSupplementalCashFlowInformation false R33.xml false Sheet 1280 - Disclosure - Valuation and Qualifying Accounts Valuation and Qualifying Accounts http://www.markwest.com/role/DisclosureValuationAndQualifyingAccounts false R34.xml false Sheet 1290 - Disclosure - Quarterly Results of Operations (Unaudited) Quarterly Results of Operations (Unaudited) http://www.markwest.com/role/DisclosureQuarterlyResultsOfOperations false R35.xml false Sheet 1300 - Disclosure - Subsequent Events Subsequent Events http://www.markwest.com/role/DisclosureSubsequentEvents false R36.xml false Sheet 9999 - Document - Document and Entity Information Document and Entity Information http://www.markwest.com/role/DocumentAndEntityInformation false R37.xml false Book All Reports All Reports false 1 28 5 0 3 189 false false D2008 85 I2009 36 I2010_PartnerCapitalMember 2 I2010SO 1 D2008_NoncontrollingInterestMember 5 D2010 111 D2008_ComprehensiveIncomeMember 3 I2008_NoncontrollingInterestMember 1 D2009_NoncontrollingInterestMember 5 D2008_AccumulatedOtherComprehensiveIncomeMember 1 I2008 2 I2010PF 1 I2010 38 I2007 2 I2007_AccumulatedOtherComprehensiveIncomeMember 1 I2008_PartnerCapitalMember 2 I2009_PartnerCapitalMember 2 D2010_NoncontrollingInterestMember 3 I2007_PartnerCapitalMember 2 D2008_PartnerCapitalMember 17 I2009_NoncontrollingInterestMember 1 D2009 72 D2010_PartnerCapitalMember 7 I2010_NoncontrollingInterestMember 1 D2009_PartnerCapitalMember 9 I2007_NoncontrollingInterestMember 1 I2009_VariableInterestEntityPrimaryBeneficiaryMember 11 I2010_VariableInterestEntityPrimaryBeneficiaryMember 11 true true