Accumulated Other Comprehensive Income (Loss) - Schedule of AOCI Activity (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2017	Aug. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (94.2)	$ (86.7)
Other comprehensive income (loss) before reclassifications	3.7	(1.9)
Less: amount reclassified from Accumulated other comprehensive income (loss)	0.5	0.7
Other comprehensive income (loss)	4.2	(1.2)
Ending balance	(90.0)	(87.9)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(45.3)	(40.0)
Other comprehensive income (loss) before reclassifications	3.7	(1.9)
Less: amount reclassified from Accumulated other comprehensive income (loss)	0.0	0.0
Other comprehensive income (loss)	3.7	(1.9)
Ending balance	(41.6)	(41.9)
Retirement benefit plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(48.9)	(46.7)
Other comprehensive income (loss) before reclassifications	0.0	0.0
Less: amount reclassified from Accumulated other comprehensive income (loss)	0.5	0.7
Other comprehensive income (loss)	0.5	0.7
Ending balance	$ (48.4)	$ (46.0)