v3.26.3
Fair Value - Financial Assets and Liabilities Recorded at FV (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Derivative Asset [Abstract]    
Derivative asset $ 79.3 $ 0.0
Cash margin receivables offset with derivatives 6.6  
Derivative assets 62.3 0.0
Derivative Liability [Abstract]    
Derivative liability 42.8 0.0
Fair Value, Recurring    
Derivative Asset [Abstract]    
Effect of netting and cash margin receivables/payables, asset (15.7)  
Derivative asset, total 63.6  
Derivative Liability [Abstract]    
Effect of netting and cash margin receivables/payables, liability (22.3)  
Derivative liability, total 20.5  
Liabilities, fair value, recurring   0.0
Assets, fair value, recurring   $ 0.0
Level 1 | Fair Value, Recurring    
Derivative Asset [Abstract]    
Derivative asset 11.5  
Derivative Liability [Abstract]    
Derivative liability 18.1  
Level 2 | Fair Value, Recurring    
Derivative Asset [Abstract]    
Derivative asset 67.8  
Derivative Liability [Abstract]    
Derivative liability 24.7  
Level 3 | Fair Value, Recurring    
Derivative Asset [Abstract]    
Derivative asset 0.0  
Derivative Liability [Abstract]    
Derivative liability 0.0  
Forward natural gas contracts    
Derivative Asset [Abstract]    
Derivative assets 62.3  
Derivative asset, noncurrent 1.3  
Forward natural gas contracts | Fair Value, Recurring    
Derivative Asset [Abstract]    
Effect of netting and cash margin receivables/payables, asset (4.2)  
Derivative asset, total 63.6  
Derivative Liability [Abstract]    
Effect of netting and cash margin receivables/payables, liability (4.2)  
Derivative liability, total 20.5  
Forward natural gas contracts | Level 1 | Fair Value, Recurring    
Derivative Asset [Abstract]    
Derivative asset 0.0  
Derivative Liability [Abstract]    
Derivative liability 0.0  
Forward natural gas contracts | Level 2 | Fair Value, Recurring    
Derivative Asset [Abstract]    
Derivative asset 67.8  
Derivative Liability [Abstract]    
Derivative liability 24.7  
Forward natural gas contracts | Level 3 | Fair Value, Recurring    
Derivative Asset [Abstract]    
Derivative asset 0.0  
Derivative Liability [Abstract]    
Derivative liability 0.0  
NYMEX/ICE Natural Gas Contracts    
Derivative Liability [Abstract]    
Derivative liability, current 13.8  
Derivative liability, noncurrent 6.7  
NYMEX/ICE Natural Gas Contracts | Fair Value, Recurring    
Derivative Asset [Abstract]    
Effect of netting and cash margin receivables/payables, asset (11.5)  
Derivative asset, total 0.0  
Derivative Liability [Abstract]    
Effect of netting and cash margin receivables/payables, liability (18.1)  
Derivative liability, total 0.0  
NYMEX/ICE Natural Gas Contracts | Level 1 | Fair Value, Recurring    
Derivative Asset [Abstract]    
Derivative asset 11.5  
Derivative Liability [Abstract]    
Derivative liability 18.1  
NYMEX/ICE Natural Gas Contracts | Level 2 | Fair Value, Recurring    
Derivative Asset [Abstract]    
Derivative asset 0.0  
Derivative Liability [Abstract]    
Derivative liability 0.0  
NYMEX/ICE Natural Gas Contracts | Level 3 | Fair Value, Recurring    
Derivative Asset [Abstract]    
Derivative asset 0.0  
Derivative Liability [Abstract]    
Derivative liability $ 0.0