Significant agreements - Ionis Share Purchase Agreement (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Jul. 09, 2021	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate purchase price		$ 234,492	$ 12,127	$ 2,716
Ionis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction price	$ 38,000	$ 38,000
Ionis | Ionis Share Purchase Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Shares issued (in shares)	282,485
Purchase price per share	$ 38.94
Aggregate purchase price	$ 11,000
Fair value of shares held	7,600
Transaction price	$ 3,400
Ionis | Ionis Share Purchase Agreement | American Depositary Shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Purchase price per share	$ 31.11