Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Income Tax Disclosure [Abstract]
Income taxes paid	$ 236.7	$ 172.5	$ 122.2
Undistributed earnings of foreign subsidiaries	147.1	172.7	194.0
Unrecognized tax benefits that would impact effective tax rates if recognized	11.9	9.7
Unrecognized tax benefits, interest and penalties accrued	0.9	0.7
Unrecognized tax benefits period increase (decrease)	1.4	(0.2)	(29.2)
Unrecognized tax benefits, increase (decrease) in accrued interest	$ 0.2	$ (0.4)	$ (0.9)