Income taxes - Schedule of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2023	Oct. 31, 2022	Oct. 31, 2021
Current
Canada	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Foreign	0.0	0.1	0.0	0.0
Current income tax provision (benefit)	0.0	0.1	0.0	0.0
Deferred and other
Canada	0.0	0.0	0.0	0.0
Foreign	0.0	0.0	0.0	0.0
Deferred income tax provision (benefit)	0.0	0.0	0.0	0.0
Income tax expense	$ 0.0	$ 0.1	$ 0.0	$ 0.0