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License and Asset Acquisitions - Schedule of IPR&D Expense (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Acquired Finite Lived Intangible Assets [Line Items] |  |  |
Total in process research and development | $ 3,600 | $ 49,659 | $ 5,500
GB002 |  |  |
Acquired Finite Lived Intangible Assets [Line Items] |  |  |
Total in process research and development |  |  | $ 5,500
GB001 |  |  |
Acquired Finite Lived Intangible Assets [Line Items] |  |  |
Total in process research and development |  | 19,148 |
GB004 |  |  |
Acquired Finite Lived Intangible Assets [Line Items] |  |  |
Total in process research and development |  | 20,000 |
GB1275 |  |  |
Acquired Finite Lived Intangible Assets [Line Items] |  |  |
Total in process research and development | 1,000 | 7,501 |
Other Programs |  |  |
Acquired Finite Lived Intangible Assets [Line Items] |  |  |
Total in process research and development | $ 2,600 | $ 3,010 |

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