Collaboration agreements - Johnson & Johnson (Details)	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2022 USD ($) target performanceObligation	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Collaboration agreements
Collaboration revenue		$ 2,293,000	$ 10,654,000	$ 11,538,000	$ 18,456,000
Deferred revenue		116,916,000	134,697,000	116,916,000	134,697,000	$ 125,314,000	$ 147,653,000
Johnson & Johnson Agreement
Collaboration agreements
Number of targets designated | target	3
Upfront payment received	$ 40,000,000
Performance obligations identified | performanceObligation	7
Revised transaction price		48,000,000		48,000,000
Johnson & Johnson Agreement | Performance obligations
Collaboration agreements
Collaboration revenue		1,800,000	7,500,000	7,900,000	$ 9,100,000
Johnson & Johnson Agreement | Development milestone achieved
Collaboration agreements
Collaboration revenue			$ 2,000,000
Johnson and Johnson 2024 CMC Arrangement
Collaboration agreements
Revised transaction price		5,000,000		5,000,000
Receivable from customer		1,600,000		1,600,000
Collaboration revenue				0
Johnson and Johnson Agreement and Johnson and Johnson 2024 CMC Arrangement
Collaboration agreements
Deferred revenue		$ 5,400,000		$ 5,400,000		$ 10,400,000