v3.24.1.u1
Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Gain) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Mar. 31, 2024
Mar. 31, 2023
Defined Benefit Plan Disclosure        
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax $ 8.3 $ 0.0 $ 8.3 $ 0.0
Pension Benefits | North America        
Components of net periodic benefit cost (gain)        
Service cost 0.5 0.5 1.0 1.1
Interest cost 1.4 1.3 2.8 2.6
Expected return on plan assets (2.0) (1.9) (4.1) (3.8)
Recognized net actuarial loss (gain) (0.1) (0.1) (0.2) (0.1)
Recognized prior service cost (credit) 0.1 0.1 0.1 0.1
Net periodic benefit cost (income) (0.1) (0.1) (0.4) (0.1)
Pension Benefits | Other International        
Components of net periodic benefit cost (gain)        
Service cost 0.1 0.0 0.1 0.0
Interest cost 6.6 5.7 12.7 11.3
Expected return on plan assets (8.9) (7.6) (17.2) (15.0)
Recognized net actuarial loss (gain) 0.0 0.1 0.1 0.1
Recognized prior service cost (credit) 0.1 0.1 0.2 0.2
Net periodic benefit cost (income) (2.1) (1.7) (4.1) (3.4)
Other Postretirement Benefit Plan | North America        
Components of net periodic benefit cost (gain)        
Service cost 0.0 0.0 0.1 0.1
Interest cost 0.6 0.7 1.3 1.3
Recognized net actuarial loss (gain) (0.2) (0.2) (0.5) (0.3)
Recognized prior service cost (credit) (0.1) (1.1) (0.3) (2.3)
Net periodic benefit cost (income) $ 0.3 $ (0.6) $ 0.6 $ (1.2)