Property and Equipment, Net of Accumulated Depreciation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	May 31, 2012
Components of property and equipment, at cost
Land and improvements	$ 7.3		$ 7.0
Buildings and improvements	97.8		96.8
Data processing equipment	175.6		212.3
Software	279.7		263.5
Furniture, fixtures, and equipment	154.4		154.2
Leasehold improvements	96.6		96.0
Construction in progress	20.1		28.2
Total property and equipment, gross	831.5		858.0
Less: Accumulated depreciation and amortization	504.6		533.7
Property and equipment, net of accumulated depreciation	326.9		324.3
Property and Equipment, Net of Accumulated Depreciation (Textual) [Abstract]
Depreciation expense	$ 19.4	$ 18.5