Accumulated Other Comprehensive Income (Loss) - Schedule of AOCI Activity (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Nov. 30, 2014	Nov. 30, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (55.2)	$ (66.7)
Other comprehensive income (loss) before reclassifications	(12.1)
Less: amount reclassified from Accumulated other comprehensive income (loss)	3.1
Other comprehensive income (loss)	(9.0)
Ending balance	(64.2)	(66.7)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(16.7)
Other comprehensive income (loss) before reclassifications	(7.5)
Less: amount reclassified from Accumulated other comprehensive income (loss)	0
Other comprehensive income (loss)	(7.5)
Ending balance	(24.2)
Retirement benefit plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(38.5)
Other comprehensive income (loss) before reclassifications	(4.6)
Less: amount reclassified from Accumulated other comprehensive income (loss)	3.1
Other comprehensive income (loss)	(1.5)
Ending balance	$ (40.0)