Accrued Expenses - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Professional fees	$ 1,707	$ 2,460
Accrued bonus	653	1,286
Accrued vacation	263	177
Accrued severance	60	179
Accrued payroll	212	213
Other	596	549
Total accrued expenses	$ 3,491	$ 4,864