Accrued Expenses - (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued professional fees	$ 281	$ 322
Accrued compensation	449	462
Accrued clinical trial expenses	525	342
Accrued other	215	134
Total accrued expenses	$ 1,470	$ 1,260