Collaboration and Licensing Agreements - Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Deferred revenue - non-current
Beginning balance	$ 4,727
Ending balance	8,563
2019 KKC Agreement
Deferred revenue - current
Beginning balance	0	$ 4,177
Decreases due to revenue recognized in the period for which cash has been received	0	(1,454)
Ending balance	0	2,723
2017 KKC Agreement
Deferred revenue - non-current
Beginning balance	4,727	0
Increases to amounts invoiced, for which cash has not yet been received	3,829	2,947
Increase due to unbilled prepayments recorded during the period	7	0
Ending balance	$ 8,563	$ 2,947