Financial Commitments & Contingencies and Key License Agreements - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 466	$ 459	$ 932	$ 851
Variable lease cost	114	108	228	215
Short-term lease cost	14	15	29	39
Total lease cost	$ 594	$ 582	$ 1,189	$ 1,105