Pensions and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Oct. 31, 2025	Oct. 31, 2024	Oct. 31, 2025	Oct. 31, 2024
Defined Benefit Pension Plans
Components of net periodic benefit cost
Service cost	$ 0.1	$ 0.3	$ 0.3	$ 0.4
Interest cost	3.8	4.4	7.6	8.8
Expected return on plan assets	(3.3)	(3.1)	(6.7)	(6.2)
Amortization of net actuarial loss (gain)	1.0	1.1	2.0	2.2
Amortization of prior service cost (credit)	0.1	0.0	0.1	0.1
Net periodic benefit cost	1.7	2.7	3.3	5.3
Other Postretirement Benefits
Components of net periodic benefit cost
Service cost	0.1	0.1	0.3	0.3
Interest cost	0.6	0.6	1.2	1.3
Expected return on plan assets	0.0	0.0	0.0	0.0
Amortization of net actuarial loss (gain)	(0.4)	(0.5)	(0.9)	(1.0)
Amortization of prior service cost (credit)	(0.2)	(0.1)	(0.3)	(0.3)
Net periodic benefit cost	$ 0.1	$ 0.1	$ 0.3	$ 0.3