Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2016	Aug. 31, 2015
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	$ (44.4)	$ (40.4)
Other comprehensive income (loss) before reclassifications from AOCL	(1.5)	0.2
Amounts reclassified from AOCL	0.3	0.2
Other comprehensive income (loss), net of tax	(1.2)	0.4
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(45.6)	(40.0)
Currency Translation Adjustments
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(1.1)	0.9
Reclassification within AOCL		(2.0)
Other comprehensive income (loss) before reclassifications from AOCL	(1.5)	0.2
Other comprehensive income (loss), net of tax	(1.5)	0.2
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(2.6)	(0.9)
Pension Plans
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(43.3)	(41.3)
Reclassification within AOCL		2.0
Amounts reclassified from AOCL	0.3	0.2
Other comprehensive income (loss), net of tax	0.3	0.2
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	$ (43.0)	$ (39.1)