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Valuation and Qualifying Accounts (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Advance royalty recoupment reserve      
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance at Beginning of Period   $ 0.0 $ 0.3
Charged to Costs and Expenses     (0.3)
Deductions     0.0
Other(2)     0.0
Balance at End of Period     0.0
Reserve for materials and supplies      
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance at Beginning of Period $ 7.2 9.5 9.0
Charged to Costs and Expenses 1.7 2.6 1.4
Deductions (5.4) (4.9) (0.9)
Other(2) 0.0 0.0 0.0
Balance at End of Period 3.5 7.2 9.5
Tax valuation allowances      
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance at Beginning of Period 1,473.5 1,451.0 2,120.8
Charged to Costs and Expenses (9.6) 0.6 (583.8)
Deductions 0.0 0.0 0.0
Other(2) (43.0) 21.9 (86.0)
Balance at End of Period $ 1,420.9 $ 1,473.5 $ 1,451.0