Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Nov. 30, 2024	Aug. 31, 2024	Nov. 30, 2023	Aug. 31, 2023	Nov. 30, 2024	Nov. 30, 2023
Accumulated Other Comprehensive Loss
Beginning Balance	$ (7.3)	$ (8.8)	$ (8.1)	$ (23.5)	$ (8.8)	$ (23.5)
Other comprehensive loss	(3.3)		(0.4)		(1.8)	0.1
Amounts reclassified from AOCL						14.9
Total other comprehensive income	(3.3)	1.5	(0.4)	15.4	(1.8)	15.0
Ending Balance	(10.6)	(7.3)	(8.5)	(8.1)	(10.6)	(8.5)
Currency Translation Adjustments
Accumulated Other Comprehensive Loss
Beginning Balance	(4.0)	(5.5)	(5.2)	(5.7)	(5.5)	(5.7)
Other comprehensive loss	(3.3)		(0.4)		(1.8)	0.1
Total other comprehensive income						0.1
Ending Balance	(7.3)	(4.0)	(5.6)	(5.2)	(7.3)	(5.6)
Pensions Plans
Accumulated Other Comprehensive Loss
Beginning Balance	(3.3)	(3.3)	(2.9)	(17.8)	(3.3)	(17.8)
Amounts reclassified from AOCL						14.9
Total other comprehensive income						14.9
Ending Balance	$ (3.3)	$ (3.3)	$ (2.9)	$ (2.9)	$ (3.3)	$ (2.9)