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Summary of Significant Accounting Policies - Summary of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Balance $ 4,977.3 $ 4,640.9
Balance 4,981.2 4,644.9
Accumulated Other Comprehensive Income (Loss) [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Balance (2.6) (2.7)
Amounts reclassified from accumulated other comprehensive income (loss) 0.1 0.2
Balance (2.5) (2.5)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member] | Pension Plan [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Balance (10.0) (8.8)
Amounts reclassified from accumulated other comprehensive income (loss) 0.3 0.2
Balance (9.7) (8.6)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member] | Other Postretirement Benefits Plan [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Balance 7.4 6.1
Amounts reclassified from accumulated other comprehensive income (loss) (0.2) (0.0)
Balance $ 7.2 $ 6.1