DEFERRED CLIENT CONVERSION AND START-UP COSTS - Schedule of Deferred Client Conversion and Start-Up Costs (Details) - USD ($) $ in Millions	Jun. 30, 2025	Jun. 30, 2024
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred client conversion and start-up costs	$ 837.5	$ 884.5
Other start-up costs	5.4	7.6
Total	$ 842.9	$ 892.1