Leases (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011
Operating Leased Assets [Line Items]
Operating lease rent expense	$ 52.2	$ 48.7	$ 45.7
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating leases minimum payments due, next 12 months	40.1
Operating leases minimum payments due, due in two years	34.5
Operating leases minimum payments due, due in three years	29.1
Operating leases minimum payments due, due in four years	22.7
Operating leases minimum payments due, due in five years	17.6
Operating leases minimum payments due, due therafter	$ 65.5
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