Fair value of financial instruments - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 71.3		$ 71.3		$ 121.0
Other Income
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success Payment Liability, Payable	1.7	$ 0.7	1.7	$ 0.1
Harvard and Board
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, payable	10,000.0		10,000.0
Harvard | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, payable	$ 31.3		$ 31.3