Corporate Investments and Funds Held for Clients - Schedule of Expected Maturities of Available-For-Sale Securities (Details) - USD ($) $ in Millions	Sep. 30, 2025	Jun. 30, 2025
Investments, Debt and Equity Securities [Abstract]
One year or less	$ 7,747.6
One year to two years	4,548.1
Two years to three years	5,598.5
Three years to four years	5,572.6
After four years	12,185.5
Total available-for-sale securities	$ 35,652.3	$ 33,777.7