v3.25.2
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Reclassification (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Mar. 31, 2025
Jun. 30, 2024
Mar. 31, 2024
Jun. 30, 2025
Jun. 30, 2024
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)            
Commodity cash flow hedges $ 747.7   $ 851.6   $ 1,468.7 $ 1,695.0
Total before tax (103.0)   (47.5)   (175.4) (117.6)
Tax effect 2.5   20.3   9.1 25.7
Total, net of tax (105.5) $ (79.0) (67.8) $ (75.5) (184.5) (143.3)
Amortization of pension and other postretirement benefit plan items | Reclassified from AOCI to net income (loss)            
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)            
Net curtailment and settlement gain (0.8)       (0.8)  
Total before tax (1.7)   (0.6)   (2.7) (1.1)
Tax effect 0.2   0.2   0.6 0.3
Total, net of tax (1.5)   (0.4)   (2.1) (0.8)
Prior service credit | Reclassified from AOCI to net income (loss)            
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)            
Prior service credit (0.2)   (0.1)   (0.5) (0.2)
Net actuarial (gain) loss | Reclassified from AOCI to net income (loss)            
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)            
Net actuarial (gain) loss (0.7)   (0.5)   (1.4) (0.9)
Cash flow hedging items | Reclassified from AOCI to net income (loss)            
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)            
Total before tax 0.8   2.8   1.1 7.6
Tax effect (0.1)   (0.3)   (0.1) (0.8)
Total, net of tax 0.7   2.5   1.0 6.8
Cash flow hedging items | Reclassified from AOCI to net income (loss) | Commodity cash flow hedges            
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)            
Commodity cash flow hedges $ 0.8   $ 2.8   $ 1.1 $ 7.6