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Collaboration and Other Agreements - NIAID Contract (Details) |  | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Sep. 15, 2015 USD ($) Molecule | Sep. 30, 2019 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2019 USD ($) | Sep. 30, 2018 USD ($) | Dec. 31, 2017 USD ($)
Collaboration And Other Agreements [Line Items] |  |  |  |  |  |
Revenues |  | $ 18,741,000 | $ 20,798,000 | $ 38,996,000 | $ 44,327,000 |
NIAID |  |  |  |  |  |
Collaboration And Other Agreements [Line Items] |  |  |  |  |  |
Commercialization of molecules | Molecule | 2 |  |  |  |  |
Base period | $ 7,500,000 |  |  |  |  |
Additional development funding options under agreement | 17,000,000.0 |  |  |  |  |
Total potential value | $ 24,500,000 |  |  |  |  |
Proceeds from additional development funding options under agreement |  |  |  |  |  | $ 10,800,000
Revenues From Grants | NIAID |  |  |  |  |  |
Collaboration And Other Agreements [Line Items] |  |  |  |  |  |
Revenues |  | $ 800,000 | $ 200,000 | $ 1,500,000 | $ 600,000 |

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