Fair value of financial instruments - Note Purchase Agreement and Oxford Loan Agreement (Details) $ in Millions	Jun. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)
Notes
Financial liabilities
Aggregate principal amount	$ 75.0
Debt, fair value	73.8	$ 76.3
Difference in fair value and principle amount	$ (1.2)	$ 1.3
Level 3 \| Discount rate, notes \| Maximum
Financial liabilities
Discount rate	0.142	0.13
Level 3 \| Discount rate, notes \| Minimum
Financial liabilities
Discount rate	0.139	0.126

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Name:	us-gaap_DebtInstrumentFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant