Significant agreements - Genentech Collaboration Agreement (Details) $ in Thousands		1 Months Ended		3 Months Ended		12 Months Ended
	Feb. 21, 2020 USD ($) item	Dec. 31, 2022 USD ($)	Nov. 30, 2021 USD ($)	Mar. 31, 2024 USD ($) item	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	Oct. 31, 2021 USD ($)	Mar. 31, 2021 USD ($)
Significant agreements.
Deferred revenue		$ 61,873		$ 114,547		$ 135,194
Collaboration revenues				19,530	$ 4,896
Genentech
Significant agreements.
Number of potential development candidates | item	4
Upfront cash payment	$ 30,000
Number of immuno oncology targets | item	2
Additional number of immuno oncology targets | item	2
Expansion Fee	$ 10,000
Milestone payments, receivable									$ 2,000
Transaction price	31,000			33,000					$ 33,000
Deferred revenue		39,308		17,278		29,104
Collaboration revenues				$ 11,611	$ 2,112
Genentech | Royalty
Significant agreements.
Number of years over which royalty is payable				10 years
Genentech | Maximum
Significant agreements.
Milestone payments, receivable	200,000
Genentech | Development milestone | Maximum
Significant agreements.
Milestone payments, receivable	65,000
Genentech | Regulatory milestone | Maximum
Significant agreements.
Milestone payments, receivable	$ 135,000
Genentech | Collaboration Program 1 Performance Obligation
Significant agreements.
Transaction price				$ 4,019
Genentech | Collaboration Program 2 Performance Obligation
Significant agreements.
Transaction price				8,037
Genentech | Collaboration Program 3 Performance Obligation
Significant agreements.
Expansion Fee			$ 10,000
Milestone payments, receivable								$ 1,000
Transaction price								11,000
Material rights								$ 3,500
Amount of estimate of variable consideration		2,000
Collaboration revenues		$ 8,400		10,400
Revenue recognized				7,500
Genentech | Collaboration Program 3 Performance Obligation | Maximum
Significant agreements.
Period over which performance obligations will be performed		3 years
Genentech | Collaboration Program 3 Performance Obligation | Minimum
Significant agreements.
Period over which performance obligations will be performed		2 years
Genentech | Collaboration Program 4 Performance Obligation
Significant agreements.
Transaction price						10,000
Deferred revenue		$ 100
Material rights						3,500
Collaboration revenues						$ 5,300
Genentech | Specified Targeting Arm Material Right Arm Program One
Significant agreements.
Number of initial collaboration programs exercised | item	1
Option fee for development and exploitation rights	$ 1,000
Milestone payments, receivable	$ 1,000
Transaction price				352
Genentech | Material rights for associated and limited substitution rights
Significant agreements.
Transaction price				$ 1,187
Deferred revenue		700
Genentech | Two material rights associated with the LSR Go Option for Collaboration Programs One And Two
Significant agreements.
Number of collaboration programs | item	2			2
Number of expansion option collaboration programs | item				2
Transaction price				$ 12,400
Genentech | Material rights associated with the LSR Go Option for Collaboration Programs One
Significant agreements.
Deferred revenue							$ 6,000
Genentech | Material rights associated with the LSR Go Option for Collaboration Programs Three
Significant agreements.
Deferred revenue		$ 7,400
Genentech | Two material rights for Expansion Options
Significant agreements.
Number of expansion option collaboration programs | item	2
Transaction price				$ 7,005
Genentech | Collaboration Program One and Two Performance Obligation
Significant agreements.
Material rights exercise period				4 years
Genentech | Collaboration Program One and Two Performance Obligation | Maximum
Significant agreements.
Regulatory, and initial commercialization milestones, payments receivable	$ 200,000
Period over which performance obligations will be performed				3 years
Genentech | Collaboration Program One and Two Performance Obligation | Minimum
Significant agreements.
Period over which performance obligations will be performed				2 years