Corporate Investments and Funds Held for Clients - Narrative (Details) - USD ($)	12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 37,701,300,000	$ 33,777,700,000
Client fund obligation repayment period	1 year
Client funds obligations	$ 44,415,500,000	$ 31,343,300,000
Funds held for clients held-in grantor trust	$ 38,969,200,000
Client funds investments with original maturities	90 days
Asset Backed Auto Loan Receivables
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 968,700,000
Fixed Rate Credit Card
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	853,100,000
Asset-Backed Securities, Device Payment Plan Agreement Receivables
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	359,200,000
Federal Farm Credit Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	654,000,000.0
Federal Home Loan Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	135,400,000
Debt Security, Corporate, Non-US
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	737,800,000
Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	557,700,000
Commercial Mortgage-Backed Securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	320,200,000
Supranational Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	230,200,000
Fair Value, Inputs, Level 1
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	0
Fair Value, Inputs, Level 3
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 0