v3.26.3
Accumulated Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Jun. 30, 2026
Mar. 31, 2026
Sep. 30, 2025
Jun. 30, 2025
Mar. 31, 2025
Sep. 30, 2026
Sep. 30, 2025
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Beginning balance $ 943.8 $ 877.3 $ 826.1 $ 776.0 $ 756.8 $ 743.1 $ 826.1 $ 743.1
Other comprehensive income (loss), net of tax 9.8 (22.3) 5.2 (0.5) 4.1 2.6 (7.3) 6.2
Ending balance 975.5 943.8 877.3 806.1 776.0 756.8 975.5 806.1
Defined Benefit Plans:                
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Beginning balance 22.9   22.5 19.6   19.1 22.5 19.1
Less: income tax (benefit) expense [1] (0.1)     (0.1)     (0.3) (0.3)
Net loss (gain) reclassified from AOCI to Net income 0.3     0.2     0.7 0.8
Other comprehensive income (loss), net of tax 0.3     0.2     0.7 0.7
Ending balance 23.2 22.9   19.8 19.6   23.2 19.8
Defined Benefit Plans: Actuarial Loss                
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Unrealized gain on cash flow hedges               (0.1)
Net unrealized gain on cash flow hedges               (0.1)
Reclassification of unrealized loss (gain) upon settlement of cash flow hedges [2] (0.6)     (0.7)     (1.8) (1.8)
Defined Benefit Plans: Net Prior Service Cost                
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Reclassification of unrealized loss (gain) upon settlement of cash flow hedges [2] 1.0     1.0     2.8 2.9
Cash Flow Hedges:                
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Beginning balance (13.2)   4.3 7.6   1.4 4.3 1.4
Unrealized gain on cash flow hedges 6.0     9.0     5.2 25.2
Less: income tax (benefit) expense (1.4)     (2.1)     (1.2) (5.9)
Net unrealized gain on cash flow hedges 4.6     6.9     4.0 19.3
Reclassification of unrealized loss (gain) upon settlement of cash flow hedges 6.5     (10.0)     (15.6) (18.0)
Less: income tax (benefit) expense [1] (1.6)     2.4     3.6 4.2
Net loss (gain) reclassified from AOCI to Net income 4.9     (7.6)     (12.0) (13.8)
Other comprehensive income (loss), net of tax 9.5     (0.7)     (8.0) 5.5
Ending balance (3.7) [3] (13.2)   6.9 [3] 7.6   (3.7) [3] 6.9 [3]
Accumulated Other Comprehensive Income (Loss)                
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Beginning balance 9.7 32.0 26.8 27.2 23.1 20.5 26.8 20.5
Other comprehensive income (loss), net of tax 9.8 (22.3) 5.2 (0.5) 4.1 2.6    
Ending balance $ 19.5 $ 9.7 $ 32.0 $ 26.7 $ 27.2 $ 23.1 $ 19.5 $ 26.7
[1] Income tax amounts reclassified out of AOCI were included as a component of Income tax provision.
[2] Amounts amortized out of AOCI related to pension and other postretirement and postemployment benefits were included within Net periodic postretirement and postemployment benefit cost (see Note 3).
[3] As of September 30, 2026, we estimate a net mark-to-market loss before tax of $5.7 million in AOCI will be reclassified into Net income upon settlement within the next 12 months.