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Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Collaborations, licenses and milestones | $ 10,941 | $ 7,090 | $ 13,340 | $ 4,340 | $ 6,440 | $ 7,821 | $ 66,007 | $ 7,252 | $ 35,711 | $ 87,520 | $ 27,762
Accounting Standard Update 2016 09 | Additional Paid-in Capital |  |  |  |  |  |  |  |  |  |  |
Adoption of ASU 2016-09 | 400 |  |  |  |  |  |  |  | 400 |  |
Accounting Standard Update 2016 09 | Accumulated Deficit |  |  |  |  |  |  |  |  |  |  |
Adoption of ASU 2016-09 | $ (400) |  |  |  |  |  |  |  | (400) |  |
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 |  |  |  |  |  |  |  |  |  |  |
Collaborations, licenses and milestones |  |  |  |  |  |  |  |  | $ 10,400 | $ 21,500 |

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