Corporate Investments and Funds Held For Clients (Classification Of Corporate Investments On The Consolidated Balance Sheets) (Details) - USD ($) $ in Millions		Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019
Corporate Investments And Funds Held For Clients [Abstract]
Cash and cash equivalents		$ 1,613.1	$ 1,908.5	$ 1,403.9
Short-term marketable securities	[1]	3.4	0.0
Long-term marketable securities	[2]	0.0	13.6
Total corporate investments		$ 1,616.5	$ 1,922.1

[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.