Deferred Client Conversion And Start-Up Costs - Schedule of Deferred Client Conversion and Start-Up Costs (Details) - USD ($) $ in Millions	Dec. 31, 2024	Jun. 30, 2024
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred client conversion and start-up costs	$ 856.9	$ 884.5
Other start-up costs	6.8	7.6
Total	$ 863.8	$ 892.1