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Asset Retirement Obligation (Details)
$ in Millions
9 Months Ended 12 Months Ended
Sep. 30, 2025
USD ($)
Sep. 30, 2024
USD ($)
Dec. 31, 2024
USD ($)
Mar. 07, 2024
USD ($)
Dec. 31, 2023
USD ($)
Jul. 27, 2018
USD ($)
ARO Loss Contingencies [Line Items]            
Asset Retirement Obligation, Liabilities Incurred $ 16.2   $ 29.8      
Number Of Consent Decrees 2          
Asset Retirement Obligation $ 2,538.9   2,572.2   $ 2,213.4  
Surety Bonds Outstanding Delivered To EPA       $ 327.1    
Asset retirement obligations $ 2,253.7   2,219.4      
Number Of Decades Remaining For Trust 3          
Asset Retirement Obligation, Liabilities Settled $ (217.2)   (253.8)      
Accretion expense for asset retirement obligations 97.5 $ 80.9 111.2      
Asset Retirement Obligation, Revision of Estimate 70.0   541.4      
Asset Retirement Obligation, Foreign Currency Translation Gain (Loss) 40.1   (69.8)      
Asset Retirement Obligation, Reclass to Held for Sale (39.9)   0.0      
Asset retirement obligations 285.2   352.8      
Unfavorable Regulatory Action | 2015 Consent Decrees With EPA            
ARO Loss Contingencies [Line Items]            
Asset retirement obligations, undiscounted     2,300.0      
Asset Retirement Obligation     1,100.0      
Bonnie Facility Trust [Member]            
ARO Loss Contingencies [Line Items]            
Assets Held-in-trust, Current           $ 21.0
Plant City and Bonnie Facilities            
ARO Loss Contingencies [Line Items]            
Asset retirement obligations $ 342.5   $ 368.7