Corporate Investments and Funds Held for Clients - Expected Maturities of Available-for-Sale Securities (Details) - USD ($) $ in Millions	Jun. 30, 2026	Jun. 30, 2025
Corporate Investments And Funds Held For Clients [Abstract]
One year or less	$ 5,871.3
One year to two years	5,668.1
Two years to three years	6,585.0
Three years to four years	8,075.4
After four years	11,501.5
Total available-for-sale securities	$ 37,701.3	$ 33,777.7