Annual report pursuant to Section 13 and 15(d)

Legal Proceedings, Commitments and Contingencies - Additional Information (Details)

v3.6.0.2
Legal Proceedings, Commitments and Contingencies - Additional Information (Details)
$ in Millions
12 Months Ended
Dec. 31, 2016
USD ($)
Building
RenewalOption
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Commitments And Contingencies [Line Items]      
Estimate of milestone payments $ 7.5    
Operating leases, number of successive renewal options | RenewalOption 2    
Operating leases, extended lease term 5 years    
Operating leases, total rental expense $ 3.8 $ 3.7 $ 3.5
Capital leases, lease terms 3 years    
Agenus West, LLC [Member]      
Commitments And Contingencies [Line Items]      
Operating leases, sublease commencement date Dec. 31, 2015    
Operating leases, sublease early termination date Oct. 31, 2016    
Operating leases sublease income $ 0.3    
Operating leases, number of portions of leased buildings | Building 2