Income Taxes (Details 4) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2023	Apr. 30, 2022	Apr. 30, 2021
Reconciliation of unrecognized tax benefits
Balance at May 1,	$ 6.5	$ 10.2	$ 13.1
Increases:
Current year tax positions	0.0	0.1	0.7
Prior year tax positions	0.0	0.2	0.0
Decreases:
Expiration of statute of limitations periods	1.2	4.0	2.6
Prior year tax positions	0.0	0.0	1.0
Balance at April 30,	$ 5.3	$ 6.5	$ 10.2