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v3.25.4

Derivatives and Fair Value Measurements - Textual (Details) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2025 USD ($) | Dec. 31, 2024 USD ($) | Dec. 31, 2023 USD ($) | Sep. 30, 2026 AUD ($) $ / $ | Dec. 31, 2025 AUD ($)
Derivatives, Fair Value [Line Items] |  |  |  |  |
Revenue from physical sale of coal | $ 3,861.5 | $ 4,236.7 | $ 4,946.7 |  |
Unobservable Measurement Input, Uncertainty, Description | 10 |  |  |  |
Fair Value, Inputs, Level 1, 2 and 3 |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Net financial asset (liability) | $ 0.0 |  |  |  |
Total net assets (liabilities) |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Net financial asset (liability) | 2.7 | (2.6) |  |  |
Total net assets (liabilities) | Level 2 |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Net financial asset (liability) | 2.7 | (3.6) |  |  |
Coal Trading |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings |  |  | (2.0) |  |
Designated as Hedging Instrument |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Total Unrealized gain (loss) recognized in income on derivatives | 6.0 | (9.0) | 154.9 |  |
Foreign currency option contracts |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Derivative, Notional Amount |  |  |  |  | $ 554,000,000.0
Derivative Asset, Notional Amount |  |  |  |  | 550,000,000.0
Foreign currency option contracts | Total net assets (liabilities) |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Net financial asset (liability) | 2.7 | (3.6) |  |  |
Foreign currency option contracts | Total net assets (liabilities) | Level 2 |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Net financial asset (liability) | 2.7 | 3.6 |  |  |
Foreign currency option contracts | Designated as Hedging Instrument |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Total Unrealized gain (loss) recognized in income on derivatives | $ 6.0 | (9.0) | 7.4 |  |
Financial trading contracts | Designated as Hedging Instrument |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Total Unrealized gain (loss) recognized in income on derivatives |  |  | (11.5) |  |
Forward Contracts | Designated as Hedging Instrument |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Other Comprehensive Income (Loss), Cash Flow Hedge, Reclassification for Discontinuance, before Tax |  | $ 0.0 |  |  |
Coal derivative contracts related to forecasted sales |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Derivative, Notional Amount |  |  |  |  | $ 0
Derivative contracts related to forecasted sales | Designated as Hedging Instrument |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Total Unrealized gain (loss) recognized in income on derivatives |  |  | $ 159.0 |  |
Scenario, Forecast | Foreign currency option contracts | Minimum |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Derivative, Exchange Rate Cap | $ / $ |  |  |  | 0.70 |
Derivative, Floor Price |  |  |  | 0.60 |
Derivative, Cap Price |  |  |  | 0.69 |
Scenario, Forecast | Foreign currency option contracts | Maximum |  |  |  |  |
Derivatives, Fair Value [Line Items] |  |  |  |  |
Derivative, Exchange Rate Cap | $ / $ |  |  |  | 0.72 |
Derivative, Floor Price |  |  |  | 0.61 |
Derivative, Cap Price |  |  |  | 0.70 |

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