Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2018	Aug. 31, 2017
Accumulated Other Comprehensive Loss
Balance at beginning of the period	$ (32.0)	$ (39.9)
Other comprehensive income (loss) before reclassifications	(0.5)	0.6
Amounts reclassified from AOCL	0.3	0.3
Total other comprehensive income (loss), net of tax	(0.2)	0.9
Balance at end of the period	(32.2)	(39.0)
Currency Translation Adjustments
Accumulated Other Comprehensive Loss
Balance at beginning of the period	0.3	(1.7)
Other comprehensive income (loss) before reclassifications	(0.5)	0.6
Total other comprehensive income (loss), net of tax	(0.5)	0.6
Balance at end of the period	(0.2)	(1.1)
Pensions Plans
Accumulated Other Comprehensive Loss
Balance at beginning of the period	(32.3)	(38.2)
Amounts reclassified from AOCL	0.3	0.3
Total other comprehensive income (loss), net of tax	0.3	0.3
Balance at end of the period	$ (32.0)	$ (37.9)