Goodwill and Other Intangibles - Schedule of other intangible assets subject to amortization (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Aug. 31, 2021	Aug. 31, 2020	May 31, 2021
Finite-lived Intangible Assets [Roll Forward]
Beginning balance other intangibles subject to amortization	$ 8.4	$ 10.5	$ 10.5
Additions	0.0	0.0
Adjustments	0.0	0.0	(0.5)
Amortization expense	(0.5)	(0.6)	(2.2)
Foreign currency translation	(0.1)	0.3	0.6
Total other intangibles subject to amortization, net of accumulated amortization of $24.8, $24.1 and $22.5, respectively	7.8	10.2	8.4
Accumulated amortization of intangible assets	32.8	30.7	32.3
Total other intangibles not subject to amortization	2.1	2.1	2.1
Total other intangibles	$ 9.9	$ 12.3	$ 10.5