Property and Equipment, Net of Accumulated Depreciation (Details) - USD ($) $ in Millions	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Components of property and equipment, at cost
Land and improvements	$ 8.3	$ 8.1
Buildings and improvements	102.1	101.1
Data processing equipment	190.9	180.8
Software	391.8	344.8
Furniture, fixtures, and equipment	145.6	145.0
Leasehold improvements	106.2	101.7
Construction in progress	28.5	25.3
Total property and equipment, gross	973.4	906.8
Less: Accumulated depreciation	619.5	564.6
Property and equipment, net of accumulated depreciation	353.9	342.2
Property and Equipment, Net of Accumulated Depreciation (Textual)
Depreciation expense	$ 92.1	$ 89.1	$ 79.2