FAIR VALUE MEASUREMENTS - Fair value on a recurring basis (Details) $ in Millions	Jun. 30, 2022 USD ($) $ / shares Y	Dec. 31, 2021 USD ($)
Other long-term assets:
The company's recorded investment	$ 71.1	$ 85.6
Price Volatility Rate | Investment in Hycroft Mining Holding Corporation Warrants
Other long-term assets:
Estimates to value Warrants	88.3
Discount yield | Investment in Hycroft Mining Holding Corporation Warrants
Other long-term assets:
Estimates to value Warrants	3.0
Expected Term | Investment in Hycroft Mining Holding Corporation Warrants
Other long-term assets:
Estimates to value Warrants | Y	4.7
Exercise Price | Investment in Hycroft Mining Holding Corporation Warrants
Other long-term assets:
Estimates to value Warrants | $ / shares	1.068
Recurring basis
Other long-term assets:
Total assets at fair value	$ 49.5
Recurring basis | Investment in Hycroft Mining Holding Corporation Warrants
Other long-term assets:
Investments measured at net asset value	18.0
Recurring basis | NCM
Other long-term assets:
The company's recorded investment	5.5
Recurring basis | Hycroft
Other long-term assets:
The company's recorded investment	26.0
Recurring basis | Quoted prices in active market (Level 1)
Other long-term assets:
Total assets at fair value	31.5
Recurring basis | Quoted prices in active market (Level 1) | NCM
Other long-term assets:
The company's recorded investment	5.5
Recurring basis | Quoted prices in active market (Level 1) | Hycroft
Other long-term assets:
The company's recorded investment	26.0
Recurring basis | Significant unobservable inputs (Level 3)
Other long-term assets:
Total assets at fair value	18.0
Recurring basis | Significant unobservable inputs (Level 3) | Investment in Hycroft Mining Holding Corporation Warrants
Other long-term assets:
Investments measured at net asset value	$ 18.0