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Legal Proceedings, Commitments and Contingencies - Additional Information (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2015 USD ($) Building RenewalOption | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
Commitments And Contingencies [Line Items] |  |  |
Estimate of milestone payments | $ 57.7 |  |
Operating leases, number of successive renewal options | RenewalOption | 2 |  |
Operating leases, extended lease term | 5 years |  |
Operating leases, total rental expense | $ 3.7 | $ 3.5 | $ 3.5
Capital leases, lease term | 3 years |  |
Agenus West, LLC [Member] |  |  |
Commitments And Contingencies [Line Items] |  |  |
Operating leases, sublease commencement date | Dec. 31, 2015 |  |
Operating leases, sublease expiration date | Dec. 31, 2016 |  |
Operating leases sublease income | $ 0.3 |  |
Operating leases, number of portions of leased buildings | Building | 2 |  |

X
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X
- Definition Term of the lessee's leasing arrangement renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Operating leases, number of successive renewal options. + References No definition available. + Details
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- Details
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