Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accrued Expenses
Accrued payroll and employee benefits	$ 7,968	$ 6,113
Accrued research and development contract costs	2,871	1,590
Accrued professional fees	878	421
Other accrued expenses	283	335
Accrued expenses	$ 12,000	$ 8,459