Corporate Investments and Funds Held for Clients - Expected Maturities of Available-For-Sale Securities (Details) - USD ($) $ in Millions	Sep. 30, 2024	Jun. 30, 2024
Investments, Debt and Equity Securities [Abstract]
One year or less	$ 6,454.0
One year to two years	7,883.9
Two years to three years	4,589.9
Three years to four years	5,437.6
After four years	9,307.7
Total available-for-sale securities	$ 33,673.1	$ 31,207.5