Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Other Income and Expenses [Abstract]
Accrued employee compensation and benefits	$ 3,756	$ 2,916
Accrued external research and development expenses	3,150	1,977
Accrued professional fees	627	1,347
Other	485	221
Accrued expenses	$ 8,018	$ 6,461