Accounts Payable and Accrued Expenses - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Trade payables	$ 1,463	$ 1,088
Employee compensation, benefits, and related accruals	872	762
Consulting and contracted research	1,029	506
Professional fees	93	214
Other	59	55
Total	$ 3,516	$ 2,625