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
Aug. 31, 2016
May 31, 2016
Funds Held for Clients and Corporate Investments [Abstract]    
Funds held for clients $ 3,443.3 $ 3,997.5
Corporate investments 367.7 220.6
Long-term corporate investments 446.3 441.1
Total funds held for clients and corporate investments, Fair value $ 4,257.3 $ 4,659.2