Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accrued Expenses
Payroll and related costs	$ 1,572	$ 1,962
Clinical and nonclinical trial expenses	4,968	3,958
Professional and consulting fees	412	605
Restructuring expenses	209	1,147
Other	146	212
Total accrued expenses	7,307	7,884
Salary continuation severance benefits	$ 100	$ 700