Significant agreements - Ionis (Details) $ in Thousands		1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 09, 2021 USD ($) item	Dec. 31, 2021 USD ($)	Jan. 31, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) item	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenues				$ 3,040	$ 4,333	$ 11,278	$ 7,926
Deferred revenue		$ 71,340		58,140		$ 58,140		$ 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		$ 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				2,195	$ 2,066	$ 6,764	$ 2,066
Deferred revenue		34,115		22,161		22,161		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		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		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		34,100						$ 3,000
Amended Ionis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment		1,600
Collaboration revenues		800
Amended Ionis | Service for initial six month
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment		800
Amended Ionis | Service for additional six month
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment		$ 800