Leases (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Operating Leased Assets [Line Items]
Operating lease rent expense	$ 55.7	$ 52.2	$ 48.7
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating leases minimum payments due, next 12 months	35.3
Operating leases minimum payments due, due in two years	30.2
Operating leases minimum payments due, due in three years	24.3
Operating leases minimum payments due, due in four years	20.1
Operating leases minimum payments due, due in five years	14.3
Operating leases minimum payments due, due thereafter	$ 60.4
Minimum [Member]
Operating Leased Assets [Line Items]
Operating leases renewal option period (years)	1 year
Maximum [Member]
Operating Leased Assets [Line Items]
Operating leases renewal option period (years)	10 years