Pensions and Other Postretirement Benefits (Details 3) - USD ($) $ in Millions		12 Months Ended
		Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Change in plan assets:
Company contributions		$ 13.1	$ 5.1	$ 29.3
Defined benefit pensions		(151.9)	(179.3)
Other postretirement benefits		(64.3)	(70.0)
Defined Benefit Pension Plans
Change in benefit obligation:
Benefit obligation at beginning of year		652.3	615.5
Service cost		1.8	1.6	2.1
Interest cost		14.4	20.9	23.2
Actuarial loss (gain) (A)	[1]	10.8	61.8
Benefits paid		(35.9)	(39.6)
Settlement		(101.2)	(4.9)
Termination benefit cost		0.0	0.2	0.0
Foreign currency translation adjustments		4.6	(3.2)
Benefit obligation at end of year		546.8	652.3	615.5
Change in plan assets:
Fair value of plan assets at beginning of year		471.6	480.3
Actual return on plan assets		44.5	34.3
Company contributions		13.1	5.1
Benefits paid		(35.9)	(39.6)
Settlement		(101.2)	(4.9)
Foreign currency translation adjustments		5.7	(3.6)
Fair value of plan assets at end of year		397.8	471.6	480.3
Funded status of the plans		(149.0)	(180.7)
Defined benefit pensions		(151.9)	(179.3)
Other noncurrent assets		7.5	11.6
Accrued compensation		(4.6)	(13.0)
Other postretirement benefits		0.0	0.0
Net benefit liability		(149.0)	(180.7)
Other Postretirement Benefits
Change in benefit obligation:
Benefit obligation at beginning of year		74.5	70.1
Service cost		1.8	1.8	1.9
Interest cost		1.8	2.3	2.3
Actuarial loss (gain) (A)	[1]	(5.9)	4.4
Benefits paid		(3.4)	(3.8)
Settlement		0.0	0.0
Termination benefit cost		0.0	0.0	0.2
Foreign currency translation adjustments		0.8	(0.3)
Benefit obligation at end of year		69.6	74.5	70.1
Change in plan assets:
Fair value of plan assets at beginning of year		0.0	0.0
Actual return on plan assets		0.0	0.0
Company contributions		3.4	3.8
Benefits paid		(3.4)	(3.8)
Settlement		0.0	0.0
Foreign currency translation adjustments		0.0	0.0
Fair value of plan assets at end of year		0.0	0.0	$ 0.0
Funded status of the plans		(69.6)	(74.5)
Defined benefit pensions		0.0	0.0
Other noncurrent assets		0.0	0.0
Accrued compensation		(5.3)	(4.5)
Other postretirement benefits		(64.3)	(70.0)
Net benefit liability		$ (69.6)	$ (74.5)

[1] The actuarial losses and gains for our defined benefit pension plans and other postretirement benefits were primarily due to changes in the discount rates used in determining the plan obligations.