Income Taxes - Net deferred tax assets (Details) - USD ($) $ in Thousands |
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|---|---|
| Deferred tax assets: | ||||
| Net operating loss carryforwards | $ 145,990 | $ 97,791 | ||
| Research and development tax credit carryforwards | 36,161 | 23,524 | ||
| Accrued expenses | 2,137 | 2,241 | ||
| Capitalized intellectual property costs | 1,746 | 1,123 | ||
| Capitalized research and development expense | 86 | 97 | ||
| Operating lease liabilities | 10,194 | 11,394 | ||
| Stock-based compensation expense | 21,483 | 15,847 | ||
| Total deferred tax assets | 217,797 | 152,017 | ||
| Deferred tax liabilities: | ||||
| Operating lease assets | (9,590) | (11,050) | ||
| Depreciation and other | (1,500) | (1,090) | ||
| Total deferred tax liabilities | (11,090) | (12,140) | ||
| Valuation allowance | $ (206,707) | $ (139,877) | $ (85,884) | $ (33,666) |