Corporate Investments and Funds Held For Clients (Classification Of Corporate Investments On The Consolidated Balance Sheets) (Details) - USD ($) $ in Millions		Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Corporate Investments And Funds Held For Clients [Abstract]
Cash and cash equivalents (A)		$ 2,785.6	$ 2,170.0	$ 1,773.4
Short-term marketable securities	[1]	3.4	3.3
Long-term marketable securities	[2]	7.2	7.2
Total corporate investments		$ 2,796.2	$ 2,180.5

[1] (a) - Short-term marketable securities are included within Other current assets on the Consolidated Balance Sheets.

[2] (b) - Long-term marketable securities are included within Other assets on the Consolidated Balance Sheets.