Leases (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Operating Leased Assets [Line Items]
Operating Leases, Current Due	$ 36.9
Operating Leases, Due in Two Years	30.8
Operating Leases, Due in Three Years	25.1
Operating Leases, Due in Four Years	20.1
Operating Leases, Due in Five Years	14.5
Operating Leases, Due Thereafter	60.2
Operating Leases, Rent Expense	$ 48.7	$ 45.7	$ 38.0
Minimum [Member]
Operating Leased Assets [Line Items]
Operating Leases, Renewal Option Period (in years)	1 year
Maximum [Member]
Operating Leased Assets [Line Items]
Operating Leases, Renewal Option Period (in years)	10 years