Significant agreements - Deferred revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred revenue
Deferred revenue	$ 35,710	$ 35,156	$ 5,657
AstraZeneca
Deferred revenue
Deferred revenue	3,560	3,756	$ 4,913
AstraZeneca | Target 3, Target 4, Target 5 and Target 6 Material Rights
Deferred revenue
Deferred revenue	3,600
Genentech
Deferred revenue
Deferred revenue	28,377	$ 27,579
Genentech | Deferred revenue material rights option
Deferred revenue
Deferred revenue	$ 20,700