v3.25.4
FAIR VALUE MEASUREMENTS (Measured on Recurring Basis) (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Obligation to receive cash collateral posted against derivative obligations $ 5.7 $ 15.1
ASSETS    
Commodity contracts, effect of counter-party netting (5.7) (15.1)
Fair Value, Measurements, Recurring | Commodity Contract    
Liabilities    
Commodity contracts 9.7 14.0
Commodity contracts, effect of counter-party netting (9.7) (14.0)
Commodity contracts, net carrying value on Balance Sheet 0.0 0.0
Fair Value, Measurements, Recurring | Renewable Energy Credit and Emissions Obligation    
Liabilities    
Commodity contracts, effect of counter-party netting 0.0 0.0
Renewable energy credit and emissions obligations 574.8 465.9
Level 1 | Fair Value, Measurements, Recurring | Commodity Contract    
Liabilities    
Commodity contracts 9.6 14.0
Level 1 | Fair Value, Measurements, Recurring | Renewable Energy Credit and Emissions Obligation    
Liabilities    
Renewable energy credit and emissions obligations 0.0 0.0
Level 2 | Fair Value, Measurements, Recurring | Commodity Contract    
Liabilities    
Commodity contracts 0.1 0.0
Level 2 | Fair Value, Measurements, Recurring | Renewable Energy Credit and Emissions Obligation    
Liabilities    
Renewable energy credit and emissions obligations 574.8 465.9
Level 3 | Fair Value, Measurements, Recurring | Commodity Contract    
Liabilities    
Commodity contracts 0.0 0.0
Level 3 | Fair Value, Measurements, Recurring | Renewable Energy Credit and Emissions Obligation    
Liabilities    
Renewable energy credit and emissions obligations 0.0 0.0
Money market funds | Fair Value, Measurements, Recurring    
ASSETS    
Money market funds 14.2 21.0
Money market funds | Level 1 | Fair Value, Measurements, Recurring    
ASSETS    
Money market funds 14.2 21.0
Money market funds | Level 2 | Fair Value, Measurements, Recurring    
ASSETS    
Money market funds 0.0 0.0
Money market funds | Level 3 | Fair Value, Measurements, Recurring    
ASSETS    
Money market funds 0.0 0.0
Commodity Contract | Fair Value, Measurements, Recurring    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Obligation to receive cash collateral posted against derivative obligations 9.7 14.0
ASSETS    
Commodity contracts 20.1 16.0
Commodity contracts, effect of counter-party netting (9.7) (14.0)
Commodity contracts, net carrying value on Balance Sheet 10.4 2.0
Commodity Contract | Level 1 | Fair Value, Measurements, Recurring    
ASSETS    
Commodity contracts 8.2 16.0
Commodity Contract | Level 2 | Fair Value, Measurements, Recurring    
ASSETS    
Commodity contracts 11.9 0.0
Commodity Contract | Level 3 | Fair Value, Measurements, Recurring    
ASSETS    
Commodity contracts $ 0.0 $ 0.0