Significant agreements - Ionis (Details) $ in Thousands		1 Months Ended			12 Months Ended
	Jul. 09, 2021 USD ($) item	Oct. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jan. 31, 2021 USD ($)	Dec. 31, 2022 USD ($) item	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenues					$ 14,463	$ 11,697	$ 10,390
Deferred revenue			$ 71,340		$ 61,873	71,340	35,156
Ionis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of material rights associated with future payments | item					4
Number of collaboration targets | item	4
Total transaction price initially determined	$ 38,000				$ 38,000
Upfront cash payment	31,000
Estimated amount payable to CROs	600
Expected period for satisfaction of performance obligations					3 years
Material rights exercise period					4 years
Collaboration revenues					$ 9,347	4,242	0
Deferred revenue			34,115		21,489	$ 34,115	3,000
Ionis | Combined licenses and research and discovery performance obligation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total transaction price initially determined					34,100
Ionis | Four material rights associated with credits for IND Acceptance fees
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total transaction price initially determined					3,900
Ionis | Ionis Share Purchase Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total transaction price initially determined	3,400
Ionis Evaluation and Option Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment	$ 3,000			$ 3,000	$ 3,000		3,000
Deferred revenue							$ 3,000
Amended Ionis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment			1,600
Collaboration revenues		$ 800	$ 800