v3.25.2
Other Comprehensive Income: Accumulated Other Comprehensive Income (Details) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Beginning balance $ 3,585.2 $ 3,305.8
Ending balance 3,719.4 3,443.4
Accumulated Other Comprehensive Income (Loss)    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Beginning balance (9.4) (14.8)
Other comprehensive income (loss), before reclassifications (0.2) (0.2)
Amounts reclassified from AOCI 1.6 3.7
Ending balance (8.0) (11.3)
Accumulated Defined Benefit Plans Adjustment    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Beginning balance (5.3) (6.2)
Other comprehensive income (loss), before reclassifications 0.0 0.0
Amounts reclassified from AOCI 0.1 0.1
Ending balance (5.2) (6.1)
Interest Rate Swap | Cash Flow Hedging    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Beginning balance (3.8) (6.1)
Other comprehensive income (loss), before reclassifications 0.0 0.0
Amounts reclassified from AOCI 1.1 1.1
Ending balance (2.7) (5.0)
Commodity Contract | Cash Flow Hedging    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Beginning balance (0.3) (2.5)
Other comprehensive income (loss), before reclassifications (0.2) (0.2)
Amounts reclassified from AOCI 0.4 2.5
Ending balance $ (0.1) $ (0.2)