Significant agreements - Deferred revenue (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred revenue
Contract assets	$ 0	$ 0
Deferred revenue	71,340,000	35,156,000	$ 5,657,000
Deferred revenue material rights option
Deferred revenue
Deferred revenue	3,900,000
Target 4 and Target 5 Material Rights
Deferred revenue
Deferred revenue	2,400,000
Ionis
Deferred revenue
Deferred revenue	34,115,000	3,000,000
Genentech
Deferred revenue
Deferred revenue	34,436,000	27,579,000
Genentech | Deferred revenue material rights option
Deferred revenue
Deferred revenue	24,900,000
AstraZeneca
Deferred revenue
Deferred revenue	$ 2,361,000	$ 3,756,000	$ 4,913,000