2.4.0.6 Html 99 251 1 false 39 0 false 5 false false R1.htm 0000 - Document - Document and Entity Information Sheet http://www.merrimackpharma.com/role/DocumentAndEntityInformation Document and Entity Information true false R2.htm 0010 - Statement - Condensed Consolidated Balance Sheets Sheet http://www.merrimackpharma.com/role/BalanceSheet Condensed Consolidated Balance Sheets false false R3.htm 0015 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) Sheet http://www.merrimackpharma.com/role/BalanceSheetParenthetical Condensed Consolidated Balance Sheets (Parenthetical) false false R4.htm 0020 - Statement - Condensed Consolidated Statements of Comprehensive Income (Loss) Sheet http://www.merrimackpharma.com/role/StatementOfIncome Condensed Consolidated Statements of Comprehensive Income (Loss) false false R5.htm 0030 - Statement - Condensed Consolidated Statements of Cash Flows Sheet http://www.merrimackpharma.com/role/CashFlows Condensed Consolidated Statements of Cash Flows false false R6.htm 1010 - Disclosure - Nature of the Business Sheet http://www.merrimackpharma.com/role/DisclosureNatureOfTheBusiness Nature of the Business false false R7.htm 1020 - Disclosure - Summary of Significant Accounting Policies Sheet http://www.merrimackpharma.com/role/DisclosureSummaryOfSignificantAccountingPolicies Summary of Significant Accounting Policies false false R8.htm 1030 - Disclosure - Initial Public Offering Sheet http://www.merrimackpharma.com/role/DisclosureInitialPublicOffering Initial Public Offering false false R9.htm 1040 - Disclosure - Net Loss Per Common Share Sheet http://www.merrimackpharma.com/role/DisclosureNetLossPerCommonShare Net Loss Per Common Share false false R10.htm 1050 - Disclosure - License and Collaboration Agreements Sheet http://www.merrimackpharma.com/role/DisclosureLicenseAndCollaborationAgreements License and Collaboration Agreements false false R11.htm 1060 - Disclosure - Fair Value of Financial Instruments Sheet http://www.merrimackpharma.com/role/DisclosureFairValueOfFinancialInstruments Fair Value of Financial Instruments false false R12.htm 1070 - Disclosure - Accrued Expenses and Other Sheet http://www.merrimackpharma.com/role/DisclosureAccruedExpensesAndOther Accrued Expenses and Other false false R13.htm 1080 - Disclosure - Common Stock Sheet http://www.merrimackpharma.com/role/DisclosureCommonStock Common Stock false false R14.htm 1090 - Disclosure - Stock-Based Compensation Sheet http://www.merrimackpharma.com/role/DisclosureStockBasedCompensation Stock-Based Compensation false false R15.htm 1100 - Disclosure - Commitments and Contingencies Sheet http://www.merrimackpharma.com/role/DisclosureCommitmentsAndContingencies Commitments and Contingencies false false R16.htm 1110 - Disclosure - Related Party Transactions Sheet http://www.merrimackpharma.com/role/DisclosureRelatedPartyTransactions Related Party Transactions false false R17.htm 1120 - Disclosure - Subsequent Events Sheet http://www.merrimackpharma.com/role/DisclosureSubsequentEvents Subsequent Events false false R18.htm 2020 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://www.merrimackpharma.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) false false R19.htm 3020 - Disclosure - Summary of Significant Accounting Policies (Tables) Sheet http://www.merrimackpharma.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTables Summary of Significant Accounting Policies (Tables) false false R20.htm 3040 - Disclosure - Net Loss Per Common Share (Tables) Sheet http://www.merrimackpharma.com/role/DisclosureNetLossPerCommonShareTables Net Loss Per Common Share (Tables) false false R21.htm 3050 - Disclosure - License and Collaboration Agreements (Tables) Sheet http://www.merrimackpharma.com/role/DisclosureLicenseAndCollaborationAgreementsTables License and Collaboration Agreements (Tables) false false R22.htm 3060 - Disclosure - Fair Value of Financial Instruments (Tables) Sheet http://www.merrimackpharma.com/role/DisclosureFairValueOfFinancialInstrumentsTables Fair Value of Financial Instruments (Tables) false false R23.htm 3070 - Disclosure - Accrued Expenses and Other (Tables) Sheet http://www.merrimackpharma.com/role/DisclosureAccruedExpensesAndOtherTables Accrued Expenses and Other (Tables) false false R24.htm 3080 - Disclosure - Common Stock (Tables) Sheet http://www.merrimackpharma.com/role/DisclosureCommonStockTables Common Stock (Tables) false false R25.htm 3090 - Disclosure - Stock-Based Compensation (Tables) Sheet http://www.merrimackpharma.com/role/DisclosureStockBasedCompensationTables Stock-Based Compensation (Tables) false false R26.htm 4010 - Disclosure - Nature of the Business (Details) Sheet http://www.merrimackpharma.com/role/DisclosureNatureOfTheBusinessDetails Nature of the Business (Details) false false R27.htm 4011 - Disclosure - Nature of the Business (Details 2) Sheet http://www.merrimackpharma.com/role/DisclosureNatureoftheBusinessDetails2 Nature of the Business (Details 2) false false R28.htm 4020 - Disclosure - Summary of Significant Accounting Policies (Details) Sheet http://www.merrimackpharma.com/role/DisclosureSummaryOfSignificantAccountingPoliciesDetails Summary of Significant Accounting Policies (Details) false false R29.htm 4021 - Disclosure - Summary of Significant Accounting Policies (Details 2) Sheet http://www.merrimackpharma.com/role/DisclosureSummaryOfSignificantAccountingPoliciesDetails2 Summary of Significant Accounting Policies (Details 2) false false R30.htm 4022 - Disclosure - Summary of Significant Accounting Policies (Details 3) Sheet http://www.merrimackpharma.com/role/DisclosureSummaryOfSignificantAccountingPoliciesDetails3 Summary of Significant Accounting Policies (Details 3) false false R31.htm 4023 - Disclosure - Summary of Significant Accounting Policies (Details 4) Sheet http://www.merrimackpharma.com/role/Disclosure-DisclosureSummaryOfSignificantAccountingPoliciesDetails4 Summary of Significant Accounting Policies (Details 4) false false R32.htm 4030 - Disclosure - Initial Public Offering (Details) Sheet http://www.merrimackpharma.com/role/DisclosureInitialPublicOfferingDetails Initial Public Offering (Details) false false R33.htm 4040 - Disclosure - Net Loss Per Common Share (Details) Sheet http://www.merrimackpharma.com/role/DisclosureNetLossPerCommonShareDetails Net Loss Per Common Share (Details) false false R34.htm 4050 - Disclosure - License and Collaboration Agreements (Details) Sheet http://www.merrimackpharma.com/role/DisclosureLicenseAndCollaborationAgreementsDetails License and Collaboration Agreements (Details) false false R35.htm 4060 - Disclosure - Fair Value of Financial Instruments (Details) Sheet http://www.merrimackpharma.com/role/DisclosureFairValueOfFinancialInstrumentsDetails Fair Value of Financial Instruments (Details) false false R36.htm 4061 - Disclosure - Fair Value of Financial Instruments (Details 2) Sheet http://www.merrimackpharma.com/role/DisclosureFairValueOfFinancialInstrumentsDetails2 Fair Value of Financial Instruments (Details 2) false false R37.htm 4070 - Disclosure - Accrued Expenses and Other (Details) Sheet http://www.merrimackpharma.com/role/DisclosureAccruedExpensesAndOtherDetails Accrued Expenses and Other (Details) false false R38.htm 4080 - Disclosure - Common Stock (Details) Sheet http://www.merrimackpharma.com/role/DisclosureCommonStockDetails Common Stock (Details) false false R39.htm 4090 - Disclosure - Stock-Based Compensation (Details) Sheet http://www.merrimackpharma.com/role/DisclosureStockBasedCompensationDetails Stock-Based Compensation (Details) false false R40.htm 4091 - Disclosure - Stock-Based Compensation (Details 2) Sheet http://www.merrimackpharma.com/role/DisclosureStockBasedCompensationDetails2 Stock-Based Compensation (Details 2) false false R41.htm 4092 - Disclosure - Stock-Based Compensation (Details 3) Sheet http://www.merrimackpharma.com/role/DisclosureStockBasedCompensationDetails3 Stock-Based Compensation (Details 3) false false R42.htm 4100 - Disclosure - Commitments and Contingencies (Details) Sheet http://www.merrimackpharma.com/role/DisclosureCommitmentsAndContingenciesDetails Commitments and Contingencies (Details) false false R43.htm 4110 - Disclosure - Related Party Transactions (Details) Sheet http://www.merrimackpharma.com/role/DisclosureRelatedPartyTransactionsDetails Related Party Transactions (Details) false false R44.htm 4120 - Disclosure - Subsequent Events (Details) Sheet http://www.merrimackpharma.com/role/DisclosureSubsequentEventsDetails Subsequent Events (Details) false false All Reports Book All Reports Element us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue had a mix of decimals attribute values: -5 -3. Element us-gaap_ResearchAndDevelopmentExpense had a mix of decimals attribute values: -5 -3. Element us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate had a mix of decimals attribute values: 3 4. Element us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross had a mix of decimals attribute values: -5 -3. 'Monetary' elements on report '4050 - Disclosure - License and Collaboration Agreements (Details)' had a mix of different decimal attribute values. Process Flow-Through: 0010 - Statement - Condensed Consolidated Balance Sheets Process Flow-Through: Removing column 'Sep. 30, 2011' Process Flow-Through: Removing column 'Dec. 31, 2010' Process Flow-Through: 0015 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) Process Flow-Through: Removing column 'Mar. 31, 2012' Process Flow-Through: 0020 - Statement - Condensed Consolidated Statements of Comprehensive Income (Loss) Process Flow-Through: 0030 - Statement - Condensed Consolidated Statements of Cash Flows mack-20120930.xml mack-20120930.xsd mack-20120930_cal.xml mack-20120930_def.xml mack-20120930_lab.xml mack-20120930_pre.xml true true