v3.19.3.a.u2

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] |  |  |
Stock-based compensation expense | $ 81,122 | $ 72,565 | $ 40,055
Research and development |  |  |
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] |  |  |
Stock-based compensation expense | 48,259 | 37,659 | 21,679
General and administrative |  |  |
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] |  |  |
Stock-based compensation expense | 32,863 | 34,906 | 18,376
Options |  |  |
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] |  |  |
Stock-based compensation expense | 74,780 | 63,288 | 31,724
Restricted common stock and units |  |  |
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] |  |  |
Stock-based compensation expense | 5,125 | 9,277 | 8,331
Employee stock purchase plan |  |  |
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] |  |  |
Stock-based compensation expense | $ 1,217 | $ 0 | $ 0

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