Commitments and Contingencies - Operating Leases - Lease Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 31, 2019	Jan. 01, 2019
Assets and Liabilities, Lessee [Abstract]
Operating lease right-of-use asset	$ 4,300	$ 4,877	$ 4,877
Operating lease liabilities, current	1,230	1,116	1,116
Operating lease liabilities, non-current	$ 4,726	$ 5,917	$ 5,917