Significant agreements - Collaboration revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Significant agreements.
Collaboration revenues	$ 1,785	$ 1,571	$ 3,593	$ 2,700
AstraZeneca
Significant agreements.
Collaboration revenues	0	319	277	731
Dementia Discovery Fund
Significant agreements.
Collaboration revenues	154	56	237	112
Genentech
Significant agreements.
Collaboration revenues	$ 1,631	$ 1,196	$ 3,079	$ 1,857