Income taxes - Schedule of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Current
Canada	$ 0.0	$ 0.0
Foreign	0.0	0.1
Current income tax provision (benefit)	0.0	0.1
Deferred and other
Canada	0.0	0.0
Foreign	0.0	0.0
Deferred income tax provision (benefit)	0.0	0.0
Income tax expense (recovery)	$ 0.0	$ 0.1