Quarterly report pursuant to Section 13 or 15(d)

Property and Equipment, Net of Accumulated Depreciation (Components of Property and Equipment, at Cost) (Details)

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Property and Equipment, Net of Accumulated Depreciation (Components of Property and Equipment, at Cost) (Details) - USD ($)
$ in Millions
Aug. 31, 2017
May 31, 2017
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross $ 1,068.1 $ 1,051.0
Less: Accumulated depreciation 739.5 713.8
Property and equipment, net of accumulated depreciation 328.6 337.2
Land and Improvements [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross 8.3 8.3
Buildings and Improvements [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross 103.6 103.5
Data Processing Equipment [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross 207.8 199.7
Software [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross 503.9 496.1
Furniture, Fixtures, and Equipment [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross 115.3 115.2
Leasehold Improvements [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross 111.5 109.5
Construction in Progress [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross $ 17.7 $ 18.7