Summary of Significant Accounting Policies - Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Accrued Liabilities
Accrued contract payments	$ 5,188	$ 6,389
Accrued clinical trial costs	6,418	11,087
Accrued professional services	1,274	1,171
Accrued employee benefits	314	651
Accrued public reporting charges	180	164
Other current accrued liabilities	558	1,003
Total	$ 13,932	$ 20,465