Accumulated Other Comprehensive Income (Loss) - Schedule of AOCI Activity (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Feb. 28, 2015	Feb. 28, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (55.2)	$ (68.2)
Other comprehensive income (loss) before reclassifications	(19.7)
Less: amount reclassified from Accumulated other comprehensive income (loss)	3.9
Other comprehensive income (loss)	(15.8)
Ending balance	(71.0)	(68.2)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(16.7)
Other comprehensive income (loss) before reclassifications	(15.1)
Less: amount reclassified from Accumulated other comprehensive income (loss)	0
Other comprehensive income (loss)	(15.1)
Ending balance	(31.8)
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)	3.9
Other comprehensive income (loss)	(0.7)
Ending balance	$ (39.2)