Quarterly report pursuant to Section 13 or 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
Feb. 28, 2018
May 31, 2017
Funds Held for Clients and Corporate Investments [Abstract]    
Funds held for clients $ 3,944.7 $ 4,301.9
Corporate investments 97.3 138.8
Long-term corporate investments 405.4 454.0
Total funds held for clients and corporate investments, Fair value $ 4,447.4 $ 4,894.7