Pensions and Other Postretirement Benefits (Details 3) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Change in plan assets:
Company contributions	$ 5.1	$ 29.3	$ 39.6
Defined benefit pensions	(179.3)	(139.1)
Other postretirement benefits	(70.0)	(65.0)
Defined Benefit Pension Plans [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	615.5	639.7
Service cost	1.6	2.1	5.2
Interest cost	20.9	23.2	21.6
Amendments	0.0	0.0
Actuarial loss (gain)	61.8	17.0
Benefits paid	(39.6)	(33.9)
Curtailment	0.0	(1.3)
Settlement	(4.9)	(27.7)
Termination benefit cost	0.2	0.0	0.0
Foreign currency translation adjustments	(3.2)	(3.6)
Benefit obligation at end of year	652.3	615.5	639.7
Change in plan assets:
Fair value of plan assets at beginning of year	480.3	497.0
Actual return on plan assets	34.3	19.6
Company contributions	5.1	29.3
Benefits paid	(39.6)	(33.9)
Settlement	(4.9)	(27.7)
Foreign currency translation adjustments	(3.6)	(4.0)
Fair value of plan assets at end of year	471.6	480.3	497.0
Funded status of the plans	(180.7)	(135.2)
Defined benefit pensions	(179.3)	(139.1)
Other noncurrent assets	11.6	8.0
Accrued compensation	(13.0)	(4.1)
Other postretirement benefits	0.0	0.0
Net benefit liability	(180.7)	(135.2)
Other Postretirement Benefits [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	70.1	65.9
Service cost	1.8	1.9	2.0
Interest cost	2.3	2.3	2.1
Amendments	0.0	2.0
Actuarial loss (gain)	4.4	2.8
Benefits paid	(3.8)	(4.7)
Curtailment	0.0	0.0
Settlement	0.0	0.0
Termination benefit cost	0.0	0.2	0.0
Foreign currency translation adjustments	(0.3)	(0.3)
Benefit obligation at end of year	74.5	70.1	65.9
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	3.8	4.7
Benefits paid	(3.8)	(4.7)
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	(74.5)	(70.1)
Defined benefit pensions	0.0	0.0
Other noncurrent assets	0.0	0.0
Accrued compensation	(4.5)	(5.1)
Other postretirement benefits	(70.0)	(65.0)
Net benefit liability	$ (74.5)	$ (70.1)