Financial instruments and financial risk factors - Commodity Pricing Adjustments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) $ / t T	Dec. 31, 2022 USD ($) $ / t T	Oct. 31, 2022 USD ($) $ / t T	Oct. 31, 2021 USD ($) $ / t T
Cobalt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Metric tonnes subject to fair value pricing adjustments | T	2,313	4,428	4,202	1,728
10% increase in prices	$ 0.2	$ 0.8	$ 1.1	$ 0.3
10% decrease in prices	$ (0.2)	$ (0.8)	$ (1.1)	$ (0.3)
Market price per tonne | $ / t	28,660	41,337	53,462	60,407
Nickel
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Metric tonnes subject to fair value pricing adjustments | T	2,313	4,428	4,202	1,728
10% increase in prices	$ 0.3	$ 1.4	$ 1.0	$ 0.4
10% decrease in prices	$ (0.3)	$ (1.4)	$ (1.0)	$ (0.4)
Market price per tonne | $ / t	16,250	30,400	21,710	19,300