Significant agreements - Ionis Accounting Analysis (Details) $ in Thousands		1 Months Ended			3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 09, 2021 USD ($) item	Oct. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jan. 31, 2021 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) item	Jun. 30, 2023 USD ($)	Dec. 31, 2020 USD ($)	Mar. 31, 2024 USD ($)	Mar. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenues					$ 9,361	$ 11,397	$ 28,891	$ 16,293
Deferred revenue					105,613		$ 105,613					$ 135,194	$ 61,873
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
Transaction price	$ 38,000									$ 37,800
Upfront cash payment	31,000
Estimated amount payable to CROs	600									$ 400	$ 600
Expected period for satisfaction of performance obligations							3 years
Material rights exercise period							4 years
Collaboration revenues					3,027	$ 2,557	$ 8,881	$ 5,341
Deferred revenue					$ 3,576		3,576					12,464	$ 21,489
Ionis | Combined licenses and research and discovery performance obligation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction price	34,100
Ionis | Four material rights associated with credits for IND Acceptance fees
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction price	3,900
Ionis | Ionis Share Purchase Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction price	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
Deferred revenue									$ 3,000			$ 12,500
Amended Ionis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment			$ 1,600
Collaboration revenues		$ 800	$ 800
Third Amended Ionis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenues							$ 800