Development Derivative Liability - Roll Forward (Details) - Derivative $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Initial payment, net of common stock warrants	$ 2,100
Funding during the period	8,400
Change in fair value	(4,200)
SFJ Agreement | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0
Initial payment, net of common stock warrants	2,075
Funding during the period	8,449
Change in fair value	4,162
Ending balance	$ 14,686