Business Segment Information - Reconcile of Gross Profit to Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Reconciliation of segment gross profit to income before provision for income taxes (benefit)
Segment gross profit	$ 77.6	$ 66.5	$ 209.9	$ 185.5
Selling, general and administrative	(53.4)	(43.1)	(146.7)	(126.6)
Interest expense	(2.2)	(1.4)	(5.8)	(3.8)
Interest income		0.1	0.1	0.1
Other expense	(0.5)		(0.5)
Income from continuing operations before provision for income taxes (benefit)	$ 21.5	$ 22.1	$ 57.0	$ 55.2