Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands |
Mar. 31, 2020 |
Dec. 31, 2019 |
Mar. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|---|---|
| Summary of Significant Accounting Policies | ||||
| Restricted cash for the benefit of its leased properties | $ 1,700 | $ 1,700 | ||
| Restricted cash (non-current) | 1,735 | 1,735 | ||
| Cash, cash equivalents and restricted cash | 146,252 | 93,633 | $ 194,356 | $ 309,421 |
| Restricted cash | 1,700 | $ 1,900 | ||
| Restricted cash (current) | $ 0 | $ 0 |