Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 22.3	$ 28.7	$ 26.8
Related income tax benefit	5.3	6.6	6.4
Selling, Distribution And Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	23.7	28.3	26.4
Other special project costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ (1.4)	$ 0.4	$ 0.4