Corporate Investments and Funds Held for Clients - Classification of Corporate Investments on the Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Corporate Investments And Funds Held For Clients [Abstract]
Cash and cash equivalents	$ 1,641.3	$ 2,083.5	$ 1,345.0
Short-term marketable securities	24.4	14.7
Long-term marketable securities	0.0	104.6
Total corporate investments	$ 1,665.7	$ 2,202.8