Fair value measurement - BMS warrants (Details) $ in Millions		3 Months Ended		9 Months Ended
	Dec. 01, 2020 USD ($) item	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Collaboration arrangements
Number of Collaboration Targets | item	4
Collaboration Agreement, Cash Payable	$ 70.0
Derivative gain (loss) on derivative net		$ 0.0	$ 0.0	$ 0.6	$ 0.0
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]				Other Nonoperating Income (Expense).
Non-current liabilities
Collaboration arrangements
Fair value of the derivative financial liability		$ 2.2		$ 2.2		$ 2.8
Collaboration Agreement, If 70 Million Is Greater Than Five Percent Of Net Proceeds | Derecognition Of Warrants
Collaboration arrangements
Threshold Percentage Of Net Proceeds	5.0
Percentage Of Net Proceeds Payable	5
Collaboration Agreement, If 70 Million Is Lesser Than One Percent Of Net Proceeds | Derecognition Of Warrants
Collaboration arrangements
Threshold Percentage Of Net Proceeds	1
Percentage Of Net Proceeds Payable	1