Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Income Taxes [Line Items] | |||
| Interest and penalties accrued | $ 0 | ||
| Reconciliation of the beginning and ending amount of gross unrecognized tax benefits | |||
| Balance at beginning of year | 7,362 | $ 5,945 | $ 4,293 |
| Additions based on tax positions related to the current year | 1,426 | 1,416 | 1,651 |
| Additions (reductions) for tax positions of prior years | (169) | ||
| Additions for tax positions of prior years | 1 | 1 | |
| Balance at end of year | 8,619 | 7,362 | 5,945 |
| Research and development tax credit carryforward | |||
| Income Taxes [Line Items] | |||
| Unrecognized tax benefits increase | $ 1,300 | $ 1,400 | $ 1,700 |