Significant agreements - Collaboration revenues (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Significant agreements.
Collaboration revenues	$ 4,378,000	$ 1,785,000	$ 8,238,000	$ 3,593,000
Ionis
Significant agreements.
Collaboration revenues	2,255,000	0	4,569,000	0
Genentech
Significant agreements.
Collaboration revenues	872,000	1,631,000	2,346,000	3,079,000
Dementia Discovery Fund
Significant agreements.
Collaboration revenues	86,000	154,000	158,000	237,000
AstraZeneca
Significant agreements.
Collaboration revenues	$ 1,165,000	$ 0	$ 1,165,000	$ 277,000