Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Income and Expenses [Abstract]
Accrued employee compensation and benefits	$ 2,916	$ 924
Accrued external research and development expenses	1,977	754
Accrued professional fees	1,347	1,324
Other	221	249
Accrued expenses	$ 6,461	$ 3,251