Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accrued Expenses
Accrued compensation	$ 1,004	$ 1,181
Accrued contracted research costs	2,011	1,261
Accrued professional fees	248	181
Accrued other	332	655
Total	$ 3,595	$ 3,278