Financial Commitments & Contingencies and Key License Agreements - Operating Lease Balance Sheet Information (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Operating lease right-of-use assets - non-current*	$ 3,068	$ 3,806
Operating lease liabilities - current	1,731	1,683
Operating lease liabilities - non-current	1,563	2,372
Total operating lease liabilities	$ 3,294	$ 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*	$ 2,700	$ 3,400
Office equipment
Property, Plant and Equipment [Line Items]
Operating lease right-of-use assets - non-current*	$ 400	$ 400