Commitments and Contingencies - Future Undiscounted Cash Payments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Remaining 2019	$ 127
2020	30
Total cash payments remaining	157
Total accrued lease liability		$ 111
ROU Lease
Lessee, Lease, Description [Line Items]
Remaining 2019	66
2020	30
Total cash payments remaining	96
Effect of discounting	(4)
Total accrued lease liability	$ 92