v3.26.1
Employee Benefits - Summary of Components of Net Periodic Postretirement Benefit Cost (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Defined Benefit Plan Disclosure [Line Items]        
Total net periodic postretirement and postemployment benefit cost $ 1.0 $ 1.4 $ 2.1 $ 2.6
Pension Plans        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0.9 0.8 1.7 1.7
Interest cost 0.5 0.4 1.0 0.8
Expected return on plan assets (0.5) (0.3) (1.0) (0.7)
Amortization of prior service cost [1] 0.2 0.2 0.4 0.4
Total net periodic postretirement and postemployment benefit cost 1.1 1.1 2.1 2.2
Other Postretirement Benefits Plan        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0.2 0.3 0.4 0.5
Interest cost 0.9 0.8 1.8 1.7
Amortization of net actuarial gain (0.3) (0.4) (0.6) (0.9)
Total net periodic postretirement and postemployment benefit cost 0.8 0.7 1.6 1.3
Postretirement Health Coverage | Salaried VEBA        
Defined Benefit Plan Disclosure [Line Items]        
Interest cost 0.4 0.6 0.9 1.1
Expected return on plan assets (0.6) (0.6) (1.2) (1.1)
Amortization of prior service cost [1] 0.7 0.8 1.4 1.5
Amortization of net actuarial gain (0.3) (0.1) (0.6) (0.2)
Total net periodic postretirement and postemployment benefit cost $ 0.2 $ 0.7 $ 0.5 $ 1.3
[1] We amortize prior service cost on a straight-line basis over the average remaining years of service of the active plan participants.