Description of Business and Summary of Significant Accounting Policies - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|---|---|
| Reconciliation of cash, cash equivalents and restricted cash | ||||
| Cash and cash equivalents | $ 66,949,000 | $ 35,318,000 | ||
| Restricted cash | 1,778,000 | 0 | ||
| Total cash, cash equivalents and restricted cash | $ 68,727,000 | $ 35,318,000 | $ 66,145,000 | $ 77,453,000 |