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FAIR VALUE MEASUREMENTS - Fair value on a recurring basis (Details) - USD ($) $ in Millions	Dec. 31, 2024	Jul. 22, 2024	Dec. 31, 2023
Other long-term assets:
Investment in marketable equity securities	$ 53.6		$ 56.4
Corporate Borrowings:
Derivative liability		$ 233.4
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-Term Debt, Excluding Current Maturities
Recurring basis
Other long-term assets:
Total assets at fair value	$ 6.1		9.1
Corporate Borrowings:
Derivative liability	157.6
Total liabilities at fair value	157.6
Recurring basis \| Investment in Hycroft Mining Holding Corporation Warrants
Other long-term assets:
Investment in warrants	0.8		3.3
Recurring basis \| Hycroft
Other long-term assets:
Investment in marketable equity securities	5.3		5.8
Recurring basis \| Quoted prices in active market (Level 1)
Other long-term assets:
Total assets at fair value	5.3		5.8
Recurring basis \| Quoted prices in active market (Level 1) \| Hycroft
Other long-term assets:
Investment in marketable equity securities	5.3		5.8
Recurring basis \| Significant unobservable inputs (Level 3)
Other long-term assets:
Total assets at fair value	0.8		3.3
Corporate Borrowings:
Derivative liability	157.6
Total liabilities at fair value	157.6
Recurring basis \| Significant unobservable inputs (Level 3) \| Investment in Hycroft Mining Holding Corporation Warrants
Other long-term assets:
Investment in warrants	$ 0.8		$ 3.3