Face (par) amount of debt instrument at time of issuance.

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

Convertible debt - Schedule of Glencore PIK Notes (Details) - USD ($) $ in Millions	Mar. 31, 2024	Mar. 25, 2024	Mar. 11, 2024	Dec. 31, 2023	Dec. 31, 2022
Glencore Convertible Notes
Debt Conversion [Line Items]
Amount Issued	$ 306.2
Glencore Convertible Notes \| Convertible Debt
Debt Conversion [Line Items]
Amount Issued	300.3		$ 75.0	$ 225.3	$ 208.1
First A&R Glencore Note \| Convertible Debt
Debt Conversion [Line Items]
Amount Issued	116.6
Second A&R Glencore Note \| Convertible Debt
Debt Conversion [Line Items]
Amount Issued	114.6
Senior Secured Convertible Glencore Note \| Convertible Debt
Debt Conversion [Line Items]
Amount Issued	$ 75.0	$ 75.0