Financial Commitments & Contingencies and Key License Agreements - Operating Lease Balance Sheet Information (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Operating lease right-of-use assets - non-current	$ 2,662	$ 3,806
Operating lease liabilities - current	1,655	1,683
Operating lease liabilities - non-current	1,210	2,372
Total operating lease liabilities	$ 2,865	$ 4,055
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Office and research facilities
Property, Plant and Equipment [Line Items]
Operating lease right-of-use assets - non-current	$ 2,300	$ 3,400
Office equipment
Property, Plant and Equipment [Line Items]
Operating lease right-of-use assets - non-current	$ 300	$ 400