Corporate information - Narrative (Details) - USD ($) $ in Millions			3 Months Ended
	Mar. 26, 2024	Aug. 10, 2021	Mar. 31, 2024	Mar. 31, 2023	Mar. 11, 2024	Dec. 31, 2023	Oct. 23, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Operating income (loss)			$ (44.2)	$ (39.1)
Net cash used in operating activities			(29.1)	$ (22.4)
Sale of stock, consideration received on transaction		$ 315.5
Property, plant and equipment, construction budget							$ 560.0
Restructuring and related cost, number of positions expected to be eliminated, percent	17.00%
Glencore Convertible Notes
Debt Instrument [Line Items]
Amount Issued			306.2
Glencore Convertible Notes | Convertible Debt
Debt Instrument [Line Items]
Amount Issued			$ 300.3		$ 75.0	$ 225.3		$ 208.1