Employee Benefit Plans - Schedule of net periodic costs (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2021	Aug. 31, 2020
Pension Plans | Foreign Plan
Components of net periodic benefit (credit) cost:
Interest cost	$ 0.2	$ 0.2
Expected return on assets	(0.3)	(0.2)
Net amortization of prior service credit	0.0	0.0
Amortization of (gain) loss	0.2	0.1
Net periodic benefit (credit) cost	0.1	0.1
Post-Retirement Benefits
Components of net periodic benefit (credit) cost:
Interest cost	0.1	0.1
Expected return on assets	0.0	0.0
Net amortization of prior service credit	(0.2)	(0.0)
Amortization of (gain) loss	0.0	0.0
Net periodic benefit (credit) cost	$ (0.1)	$ 0.1