v3.26.1
Asset Retirement Obligation (Details)
$ in Millions
3 Months Ended 6 Months Ended
Mar. 31, 2026
USD ($)
Mar. 31, 2025
USD ($)
Jun. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Mar. 07, 2024
USD ($)
Jul. 27, 2018
USD ($)
ARO Loss Contingencies [Line Items]              
Asset Retirement Obligation, Liabilities Incurred $ 3.2   $ 22.7        
Number Of Consent Decrees 2            
Asset Retirement Obligation $ 2,527.5     $ 2,601.9 $ 2,572.2    
Surety Bonds Outstanding Delivered To EPA           $ 337.6  
Asset retirement obligations $ 2,288.5     2,330.6      
Number Of Decades Remaining For Trust 3            
Asset Retirement Obligation, Liabilities Settled $ (53.1)   (288.9)        
Accretion expense for asset retirement obligations 34.2 $ 32.2 129.7        
Asset Retirement Obligation, Revision of Estimate 0.0   190.5        
Asset Retirement Obligation, Foreign Currency Translation Gain (Loss) 5.9   37.8        
Asset Retirement Obligation, Reclass to Held for Sale (64.6)   $ 62.1        
Asset retirement obligations 239.0     271.3      
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 $ 368.5     $ 387.9