2.4.0.81100 - Disclosure - Commitments and Contingenciestruefalsefalse1false falsefalseD2013Q2YTDhttp://www.sec.gov/CIK0001274792duration2013-01-01T00:00:002013-06-30T00:00:001true 1us-gaap_CommitmentsAndContingenciesDisclosureAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Commitments and Contingencies2false 2us-gaap_CommitmentsAndContingenciesDisclosureTextBlockus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00<div style="font-size:10.0pt;font-family:Times New Roman;"> 10. Commitments and Contingencies   Operating leases   The Company leases its office, laboratory and manufacturing space under non-cancellable operating leases. During March 2013, the Company entered into a facility lease amendment to further expand its office, laboratory and manufacturing space. The amendment leased additional space effective March 2013 and is co-terminus with the existing lease. The aggregate additional rent due over the term of the lease amendment is approximately $2.6 million. As part of this amendment, the landlord agreed to reimburse the Company for an additional portion of tenant improvements made to the facility, up to a total of $0.6 million. Aggregate landlord reimbursable tenant improvements outstanding under the existing lease and the lease amendment as of June 30, 2013 is $4.8 million, which are recorded within other current assets on the condensed consolidated balance sheets.   </div>falsefalsefalsenonnum:textBlockItemTypenaThe entire disclosure for commitments and contingencies.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Interpretation (FIN) -Number 14 -Paragraph 3 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.25) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6449706&loc=d3e16207-108621 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14435-108349 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 440 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25287-109308 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 5 -Paragraph 9, 10, 11, 12 -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. false0Commitments and ContingenciesfalseCommitments and ContingenciesUnKnownUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.merrimackpharma.com/role/DisclosureCommitmentsAndContingencies12