Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accrued Expenses
Employee compensation expenses	$ 1,922	$ 3,971
Research and development expenses	704	761
Litigation settlements (see Note 17)	3,075
Other	1,230	1,174
Total accrued expenses	$ 6,931	$ 5,906