Significant agreements - Novartis Collaboration Agreement - Accounting Analysis (Details) $ in Thousands		3 Months Ended		6 Months Ended
	Mar. 27, 2023 USD ($) item	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenues		$ 11,397	$ 4,378	$ 16,293	$ 8,238
Deferred revenue		144,837		144,837		$ 61,873	$ 71,340
Novartis Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction price	$ 50,000
Collaboration revenues		0	$ 0	0	$ 0
Deferred revenue		$ 51,553		$ 51,553		$ 0
Novartis Collaboration Agreement | Two Combined Performance Obligations For First And Second Targets [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Combined performance obligations | item	2
Transaction price	$ 18,008
Novartis Collaboration Agreement | Two Material Rights Associated With Limited Substitution Rights [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of material rights | item	2
Transaction price	$ 2,466
Novartis Collaboration Agreement | Two Material Rights Associated With Options To Progress Development Candidates Incorporating Radionuclides [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of material rights | item	2
Transaction price	$ 19,684
Novartis Collaboration Agreement | Two Material Rights Associated With Options To Progress Development Candidates Not Incorporating Radionuclides [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of material rights | item	2
Transaction price	$ 9,842