Financial Commitments & Contingencies and Key License Agreements - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 459		$ 851
Short-term lease cost	108		215
Variable lease cost	15		39
Total lease cost	$ 582	$ 400	$ 1,105	$ 900