XML 29 R18.htm IDEA: XBRL DOCUMENT v2.4.1.9
Summary of Significant Accounting Policies (Details 5)
3 Months Ended 9 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2015
Mar. 31, 2014
Segment Reporting        
Number of operating segments     1us-gaap_NumberOfOperatingSegments  
Biotest | Revenue        
Collaborative Partner:        
Percentages of revenue recognized 9.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_BiotestAGMember
13.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_BiotestAGMember
4.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_BiotestAGMember
3.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_BiotestAGMember
Lilly | Revenue        
Collaborative Partner:        
Percentages of revenue recognized 1.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_EliLillyAndCompanyMember
15.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_EliLillyAndCompanyMember
24.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_EliLillyAndCompanyMember
18.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_EliLillyAndCompanyMember
Novartis | Revenue        
Collaborative Partner:        
Percentages of revenue recognized 44.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_NovartisInstitutesForBioMedicalResearchIncMember
22.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_NovartisInstitutesForBioMedicalResearchIncMember
44.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_NovartisInstitutesForBioMedicalResearchIncMember
40.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_NovartisInstitutesForBioMedicalResearchIncMember
Roche | Revenue        
Collaborative Partner:        
Percentages of revenue recognized 45.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_RocheMember
37.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_RocheMember
19.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_RocheMember
31.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesMember
/ us-gaap_MajorCustomersAxis
= imgn_RocheMember