Goodwill and Intangible Assets, Net of Accumulated Amortization (Components of Intangible Assets, at Cost) (Details) - USD ($) $ in Millions	May 31, 2022	May 31, 2021
Intangible Assets [Line Items]
Total intangible assets, gross	$ 660.4	$ 656.4
Less: Accumulated amortization	435.8	380.6
Intangible assets, net of accumulated amortization	224.6	275.8
Other Intangible Assets [Member]
Intangible Assets [Line Items]
Total intangible assets, gross	23.0	24.1
Client Lists [Member]
Intangible Assets [Line Items]
Total intangible assets, gross	$ 637.4	$ 632.3