Cash, Cash Equivalents and Investments - Fair Values and Gross Unrealized Loss of Available-For-Sale Investments (Details) - USD ($) $ in Thousands |
Sep. 30, 2021 |
Dec. 31, 2020 |
|---|---|---|
| Debt Securities, Available-for-sale [Line Items] | ||
| Adjusted Cost | $ 45,951 | $ 111,565 |
| Gross Unrealized Loss | (19) | (23) |
| Fair Value | 45,932 | 111,542 |
| U.S. government securities | ||
| Debt Securities, Available-for-sale [Line Items] | ||
| Adjusted Cost | 16,024 | 90,120 |
| Gross Unrealized Loss | (10) | (14) |
| Fair Value | 16,014 | 90,106 |
| Corporate bonds and commercial paper | ||
| Debt Securities, Available-for-sale [Line Items] | ||
| Adjusted Cost | 29,927 | 21,445 |
| Gross Unrealized Loss | (9) | (9) |
| Fair Value | $ 29,918 | $ 21,436 |