Collaboration and Licensing Agreements - Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021
Current deferred revenue
Beginning balance		$ 4,177
Ending balance	$ 1,412	1,412
Non-current deferred revenue
Beginning balance		0
Ending balance	2,947	2,947
2019 KKC Agreement
Current deferred revenue
Beginning balance		4,177
Decreases due to revenue recognized in the period for which cash has been received		(2,765)
Ending balance	1,412	1,412
2017 KKC Agreement
Non-current deferred revenue
Beginning balance		0
Increases to amounts invoiced for which cash has been received	2,900	2,947
Ending balance	$ 2,947	$ 2,947