Significant agreements - Collaboration revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Significant agreements.
Collaboration revenues	$ 1,808	$ 1,129
AstraZeneca
Significant agreements.
Collaboration revenues	277	412
Dementia Discovery Fund
Significant agreements.
Collaboration revenues	83	56
Genentech
Significant agreements.
Collaboration revenues	$ 1,448	$ 661