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Collaboration and Other Agreements, NIAID Contract (Details) - NIAID |  | 12 Months Ended
--- | --- | ---
Sep. 15, 2015 USD ($) Molecule | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Collaboration and Other Agreements [Line Items] |  |  |  |
Commercialization of molecules | Molecule | 2 |  |  |
Base period value | $ 7,500,000 |  |  |
Proceeds from additional development funding options under agreement |  | $ 10,800,000 |  |
Recognized revenue under agreement |  | $ 1,700,000 | $ 5,100,000 | $ 200,000
Maximum |  |  |  |
Collaboration and Other Agreements [Line Items] |  |  |  |
Additional development funding options | 17,000,000.0 |  |  |
Total potential value | $ 24,500,000.0 |  |  |

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