2.4.0.84090 - Disclosure - Stock-Based Compensation (Details)truefalsefalse1false falsefalseD2013Q1_M01_StockIncentivePlan2011Memberhttp://www.sec.gov/CIK0001274792duration2013-01-01T00:00:002013-01-31T00:00:00SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli02false falsefalseD2013Q2YTD_StockIncentivePlan2011Memberhttp://www.sec.gov/CIK0001274792duration2013-01-01T00:00:002013-06-30T00:00:00SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli03false falsefalseD2012Q2YTD_StockIncentivePlan2011Memberhttp://www.sec.gov/CIK0001274792duration2012-01-01T00:00:002012-06-30T00:00:00SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli04false falsefalseI2012_StockIncentivePlan2011Memberhttp://www.sec.gov/CIK0001274792instant2012-12-31T00:00:000001-01-01T00:00:00SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli01true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Stock-based compensation2false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrossus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2truefalsefalse30760003076000falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:sharesItemTypesharesGross number of share options (or share units) granted during the period.No definition available.false1Stock options issued (in shares)3false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse2false truefalseD2013Q1_M01_StockIncentivePlan2011Memberhttp://www.sec.gov/CIK0001274792duration2013-01-01T00:00:002013-01-31T00:00:00falsefalse2011 Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldimack_StockIncentivePlan2011Memberus-gaap_PlanNameAxisexplicitMemberSharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0nanafalse02011 Plan4true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Stock-based compensation5false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2truefalsefalse17000001700000falsefalsefalse3falsefalsefalse00falsefalsefalse4truefalsefalse13000001300000falsefalsefalsexbrli:sharesItemTypesharesThe difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false1Shares of common stock available for grant (in shares)6false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorizedus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse34000003400000falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:sharesItemTypesharesNumber of additional shares authorized for issuance under an established share-based compensation plan.No definition available.false1Additional common stock available for issuance (in shares)7false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrossus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2truefalsefalse300000300000falsefalsefalse3truefalsefalse300000300000falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:sharesItemTypesharesGross number of share options (or share units) granted during the period.No definition available.false1Stock options issued (in shares)falseStock-Based Compensation (Details)UnKnownNoRoundingUnKnownUnKnowntruefalsefalseSheethttp://www.merrimackpharma.com/role/DisclosureStockBasedCompensationDetails47