Annual report pursuant to Section 13 and 15(d)

Funds Held for Clients and Corporate Investments (Classification of Investments on Consolidated Balance Sheets) (Details)

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Funds Held for Clients and Corporate Investments (Classification of Investments on Consolidated Balance Sheets) (Details) - USD ($)
$ in Millions
May 31, 2018
May 31, 2017
Funds Held for Clients and Corporate Investments [Abstract]    
Funds held for clients $ 4,703.8 $ 4,301.9
Corporate investments 66.0 138.8
Long-term corporate investments 295.5 454.0
Total funds held for clients and corporate investments, Fair value $ 5,065.3 $ 4,894.7