Corporate Investments and Funds Held For Clients (Classification Of Corporate Investments On The Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Corporate Investments And Funds Held For Clients [Abstract]
Cash and cash equivalents	$ 1,745.0	$ 2,575.2	$ 1,602.2
Short-term marketable securities	19.7	10.4
Long-term marketable securities	0.0	23.5
Total corporate investments	$ 1,764.7	$ 2,609.1