Employee Benefit Plans - Schedule of change in benefit obligations (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2024	May 31, 2023	May 31, 2022
U.K. | Pension Plans
Change in benefit obligation:
Benefit obligation at beginning of year	$ 25.1	$ 31.9
Interest cost	1.3	1.0	$ 0.8
Plan participants’ contributions	0.0	0.0
Actuarial losses (gains)	0.9	(6.7)
Foreign currency translation	0.7	(0.3)
Benefits paid, including expenses	(1.3)	(0.8)
Benefit obligation at end of year	26.7	25.1	31.9
U.S. | Other Postretirement Benefits
Change in benefit obligation:
Benefit obligation at beginning of year	8.0	9.4
Interest cost	0.3	0.3	0.2
Plan participants’ contributions	0.1	0.0
Actuarial losses (gains)	(0.3)	(0.8)
Foreign currency translation	0.0	0.0
Benefits paid, including expenses	(0.9)	(0.9)
Benefit obligation at end of year	$ 7.2	$ 8.0	$ 9.4