Property and Equipment, Net of Accumulated Depreciation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Aug. 31, 2013	Aug. 31, 2012	May 31, 2013
Components of property and equipment, at cost
Land and improvements	$ 8.1		$ 8.1
Buildings and improvements	100.3		99.2
Data processing equipment	182.4		175.6
Software	300.9		290.1
Furniture, fixtures, and equipment	144.6		145.2
Leasehold improvements	100.6		99.5
Construction in progress	35.9		32.8
Total property and equipment, gross	872.8		850.5
Less: Accumulated depreciation and amortization	522.3		504.5
Property and equipment, net of accumulated depreciation	350.5		346.0
Property and Equipment, Net of Accumulated Depreciation (Textual)
Depreciation expense	$ 20.7	$ 19.4