Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Accrued Expenses
Accrued compensation	$ 1,237	$ 796
Accrued contracted research costs	800	1,109
Accrued professional fees	159	791
Accrued other	241	97
Total	$ 2,437	$ 2,793