Employee Benefit Plans - Schedule of net periodic costs (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2020	Aug. 31, 2019
Components of net periodic benefit (credit) cost:
Amortization of (gain) loss	$ 0.1	$ 0.2
Pension Plans | Foreign Plan
Components of net periodic benefit (credit) cost:
Interest cost	0.2	0.2
Expected return on assets	(0.2)	(0.2)
Net amortization of prior service credit	0.0	0.0
Amortization of (gain) loss	0.1	0.2
Net periodic benefit (credit) cost	0.1	0.2
Post-Retirement Benefits
Components of net periodic benefit (credit) cost:
Interest cost	0.1	0.2
Expected return on assets	0.0	0.0
Net amortization of prior service credit	0.0	(0.0)
Amortization of (gain) loss	0.0	0.0
Net periodic benefit (credit) cost	$ 0.1	$ 0.2