Property and Equipment, Net of Accumulated Depreciation (Components of Property and Equipment, at Cost) (Details) - USD ($) $ in Millions		May 31, 2021	May 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment, gross		$ 1,361.9	$ 1,364.6
Less: Accumulated depreciation		966.1	957.2
Property and equipment, net of accumulated depreciation		395.8	407.4
Land and Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross		10.3	10.8
Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross		158.3	166.5
Data Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross		211.4	222.4
Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	[1]	748.3	690.9
Furniture, Fixtures, and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross		99.8	116.3
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross		83.5	110.6
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	[1]	$ 50.3	$ 47.1

[1] Software includes both purchased software and costs capitalized related to internally developed software placed in service. Capitalized costs related to internally developed software that has not yet been placed in service is included in construction in progress.