Goodwill and Intangible Assets, Net of Accumulated Amortization (Components of Intangible Assets, at Cost) (Details) - USD ($) $ in Millions	Nov. 30, 2019	May 31, 2019
Intangible Assets [Line Items]
Total intangible assets, gross	$ 632.9	$ 631.2
Less: Accumulated amortization	273.2	232.1
Intangible assets, net of accumulated amortization	359.7	399.1
Other Intangible Assets [Member]
Intangible Assets [Line Items]
Total intangible assets, gross	23.2	23.0
Client Lists [Member]
Intangible Assets [Line Items]
Total intangible assets, gross	$ 609.7	$ 608.2