Pensions and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Jul. 31, 2023	Jul. 31, 2022
Components of net periodic benefit cost
Pension settlement loss (gain)	$ 3.2	$ 0.0
Defined Benefit Plan, Plan Assets, Contributions by Employer		70.0
Defined Benefit Plan, Plan Assets, Benefits Paid	0.7	0.7
Defined Benefit Pension Plans
Components of net periodic benefit cost
Service cost	0.2	0.3
Interest cost	4.6	4.4
Expected return on plan assets	(4.1)	(4.0)
Amortization of net actuarial loss (gain)	0.9	1.0
Amortization of prior service cost (credit)	0.1	0.1
Pension settlement loss (gain)	3.2	0.0
Net periodic benefit cost	4.9	1.8
Other Postretirement Benefits
Components of net periodic benefit cost
Service cost	0.2	0.2
Interest cost	0.6	0.6
Expected return on plan assets	0.0	0.0
Amortization of net actuarial loss (gain)	(0.4)	(0.3)
Amortization of prior service cost (credit)	(0.1)	(0.1)
Pension settlement loss (gain)	0.0	0.0
Net periodic benefit cost	$ 0.3	$ 0.4