Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands |
Sep. 30, 2021 |
Dec. 31, 2020 |
Sep. 30, 2020 |
Dec. 31, 2019 |
|---|---|---|---|---|
| Summary of Significant Accounting Policies | ||||
| Restricted cash for the benefit of its leased properties | $ 1,700 | $ 1,700 | ||
| Restricted cash (current) | $ 100 | $ 100 | ||
| Current restricted cash included in prepaid expense and other current assets | Prepaid expenses and other current assets | Prepaid expenses and other current assets | ||
| Restricted cash (non-current) | $ 1,573 | $ 1,573 | ||
| Cash, cash equivalents and restricted cash | 265,753 | $ 92,901 | $ 76,909 | $ 93,633 |
| Restricted cash | $ 1,700 | $ 1,700 |