v3.26.1
Employee Benefit Plans - Components of Pension and Other Postretirement Benefit Income (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Pension benefits        
Defined Benefit Plan Disclosure [Line Items]        
Interest cost $ 16.9 $ 17.4 $ 50.8 $ 52.3
Expected return on plan assets (17.9) (18.1) (53.6) (54.2)
Amortization of prior service (credits) costs 0.0 0.1 0.0 0.1
Net periodic benefit income (1.0) (0.6) (2.8) (1.8)
Other postretirement benefits        
Defined Benefit Plan Disclosure [Line Items]        
Interest cost 0.3 0.3 0.8 0.8
Expected return on plan assets 0.0 0.0 0.0 0.0
Amortization of prior service (credits) costs (0.6) (0.6) (1.7) (1.7)
Net periodic benefit income $ (0.3) $ (0.3) $ (0.9) $ (0.9)