Leases (Details) - USD ($) $ in Millions	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating leases minimum payments due, due in year one	$ 27.0
Operating leases minimum payments due, due in two years	21.2
Operating leases minimum payments due, due in three years	16.9
Operating leases minimum payments due, due in four years	11.1
Operating leases minimum payments due, due in five years	7.6
Operating leases minimum payments due, due thereafter	$ 14.9
Minimum
Operating Leased Assets [Line Items]
Operating leases renewal option period	1 year
Maximum
Operating Leased Assets [Line Items]
Operating leases renewal option period	10 years
Continuing Operations
Operating Leased Assets [Line Items]
Operating lease rent expense	$ 34.9	$ 43.5	$ 41.9