Commitments and Contingencies - Future minimum operarting lease payments (Details) (USD $) $ in Thousands |
Dec. 31, 2019
USD ($)
|
|---|---|
| Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] | |
| 2020 | $ 211 |
| 2021 | 211 |
| Total undiscounted lease payments | 422 |
| Less: present value discount | (43) |
| Total minimum lease payments | $ 379 |