Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|---|---|
| Summary of Significant Accounting Policies | ||||
| Restricted cash for the benefit of its leased properties | $ 1,700 | $ 1,700 | ||
| Restricted cash (current) | $ 100 | |||
| Current restricted cash included in prepaid expense and other current assets | ruby:PrepaidExpenseAndOtherCurrent | |||
| Restricted cash (non-current) | $ 1,573 | 1,735 | ||
| Cash, cash equivalents and restricted cash | 92,901 | 93,633 | $ 309,421 | $ 104,572 |
| Restricted cash | $ 1,700 | $ 1,700 | $ 2,300 |