Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Income Tax Disclosure [Abstract]
Income taxes paid	$ 269.6	$ 452.6	$ 236.7
Undistributed earnings of foreign subsidiaries	214.8	117.2	147.1
Unrecognized tax benefits that would impact effective tax rates if recognized	12.6	12.9
Unrecognized tax benefits, interest and penalties accrued	0.9	1.1
Unrecognized tax benefits period increase (decrease)		0.8	1.4
Unrecognized tax benefits, increase (decrease) in accrued interest	$ 0.2	$ 0.2	$ 0.2