Income Taxes (Details 4) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Reconciliation of unrecognized tax benefits
Balance at May 1,	$ 10.2	$ 13.1	$ 15.0
Increases:
Current year tax positions	0.1	0.7	1.4
Prior year tax positions	0.2	0.0	0.2
Decreases:
Expiration of statute of limitations periods	4.0	2.6	3.5
Prior year tax positions	0.0	1.0	0.0
Balance at April 30,	$ 6.5	$ 10.2	$ 13.1