Pensions and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Jul. 31, 2025	Jul. 31, 2024
Defined Benefit Pension Plans
Components of net periodic benefit cost
Service cost	$ 0.2	$ 0.1
Interest cost	3.8	4.4
Expected return on plan assets	(3.4)	(3.1)
Amortization of net actuarial loss (gain)	1.0	1.1
Amortization of prior service cost (credit)	0.0	0.1
Net periodic benefit cost	1.6	2.6
Other Postretirement Benefits
Components of net periodic benefit cost
Service cost	0.2	0.2
Interest cost	0.6	0.7
Expected return on plan assets	0.0	0.0
Amortization of net actuarial loss (gain)	(0.5)	(0.5)
Amortization of prior service cost (credit)	(0.1)	(0.2)
Net periodic benefit cost	$ 0.2	$ 0.2