Business Segment Information - Reconciliation of Gross Profit to Income (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2021	Aug. 31, 2020
Reconciliation of segment gross profit to income from continuing operations before provision for income taxes
Segment gross profit	$ 64.6	$ 48.6
Selling, general and administrative	(49.3)	(45.3)
Loss from joint ventures	(0.2)	(0.1)
Loss on sale of business	0.0	(19.5)
Other income, net	0.7	0.2
Interest expense	(0.7)	(1.7)
Interest income	0.0	0.1
Income (Loss) from continuing operations before provision for income taxes	$ 15.1	$ (17.7)