Significant agreements - Collaboration revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Significant agreements
Collaboration revenues	$ 614	$ 1,610	$ 8,520	$ 6,079
AstraZeneca
Significant agreements
Collaboration revenues	441	388	1,229	1,078
Sanofi
Significant agreements
Collaboration revenues	0	1,047	6,016	3,258
Oxurion
Significant agreements
Collaboration revenues	0	175	0	1,743
Dementia Discovery Fund
Significant agreements
Collaboration revenues	173	0	275	0
Material transfer agreement
Significant agreements
Collaboration revenues	$ 0	$ 0	$ 1,000	$ 0