Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	May 31, 2025	May 31, 2024	May 31, 2023
Income Tax Disclosure [Abstract]
Beginning Balance	$ 0.2	$ 1.2	$ 1.2
Decreases - tax positions taken in prior years		(1.0)	0.0
Increases - current tax positions	0.0	0.0	0.0
Settlements	0.0	0.0	0.0
Lapse of statutes of limitations	(0.2)	0.0	0.0
Ending Balance	$ 0.0	$ 0.2	$ 1.2