Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Development costs	$ 2,156	$ 852
Employee compensation (including reduction in workforce)	453	352
Professional fees	244	413
Other	62	157
Total accrued expenses	$ 2,915	$ 1,774