Corporate Investments and Funds Held for Clients - Narrative (Details) - USD ($)	3 Months Ended
	Sep. 30, 2026	Jun. 30, 2026
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 37,572,300,000	$ 37,701,300,000
Client fund obligation repayment period	1 year
Client funds obligations	$ 46,039,600,000	44,415,500,000
Client funds held in grantor trust	$ 39,999,700,000	$ 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	$ 1,233,700,000
Fixed Rate Credit Card
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	796,500,000
Asset-Backed Securities, Device Payment Plan Agreement Receivables
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	365,600,000
Federal Farm Credit Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	630,600,000
Federal Home Loan Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	130,200,000
Debt Security, Corporate, Non-US
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	730,400,000
Commercial Mortgage-Backed Securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	298,000,000.0
Supranational Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	227,100,000
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