Property and Equipment, Net of Accumulated Depreciation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011
Components of property and equipment, at cost
Land and improvements	$ 8.1	$ 7.0
Buildings and improvements	99.2	96.8
Data processing equipment	175.6	212.3
Software	290.1	263.5
Furniture, fixtures, and equipment	145.2	154.2
Leasehold improvements	99.5	96.0
Construction in progress	32.8	28.2
Total property and equipment, gross	850.5	858.0
Less: Accumulated depreciation and amortization	504.5	533.7
Property and equipment, net of accumulated depreciation	346.0	324.3
Property and Equipment, Net of Accumulated Depreciation (Textual)
Depreciation expense	$ 79.2	$ 74.8	$ 68.4