Commitments and Contingencies - Future Undiscounted Cash Payments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Remaining 2019	$ 84
2020	30
Total cash payments remaining	114
Total accrued lease liability		$ 111
ROU Lease
Lessee, Lease, Description [Line Items]
Remaining 2019	44
2020	30
Total cash payments remaining	74
Effect of discounting	(3)
Total accrued lease liability	$ 71