Corporate Investments and Funds Held For Clients (Classification Of Corporate Investments On The Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016
Corporate Investments And Funds Held For Clients [Abstract]
Cash and cash equivalents	$ 2,363.6	$ 2,780.4	$ 2,776.6
Short-term marketable securities	113.2	3.2
Long-term marketable securities	26.8	7.6
Total corporate investments	$ 2,503.6	$ 2,791.2