Goodwill and Other Intangibles - Schedule of activity in goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2024	May 31, 2023	May 31, 2022
Goodwill [Roll Forward]
Gross beginning balance	$ 172.3	$ 164.9
Goodwill, Impaired, Accumulated Impairment Loss	(39.6)	(39.6)	$ (39.6)
Beginning balance	132.7	125.3
Additions	0.0	7.6
Foreign currency translation	0.1	(0.2)
Gross ending balance	172.4	172.3
Ending balance	$ 132.8	$ 132.7