Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Expenses
Accrued Payroll and Employee Benefits	$ 4,575	$ 4,400
Accrued Research and Development Contract Costs	1,186	1,766
Accrued Professional Fees	400	620
Other Accrued Expenses	338	221
Accrued Expenses	$ 6,499	$ 7,007