Corporate Investments and Funds Held for Clients - Narrative (Details) - USD ($)	3 Months Ended
	Sep. 30, 2025	Jun. 30, 2025
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 35,652,300,000	$ 33,777,700,000
Client fund obligation repayment period	1 year
Client funds obligations	$ 31,845,600,000	31,343,300,000
Client funds held in grantor trust	$ 28,332,900,000	$ 27,355,200,000
Client funds investments with original maturities	90 days
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
Asset-Backed Auto Loan Receivables
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	936,600,000
Fixed Rate Credit Card
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	584,700,000
Asset-Backed Securities, Device Payment Plan Agreement Receivables
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	313,600,000
Federal Farm Credit Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	743,200,000
Federal Home Loan Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	126,800,000
Debt Security, Corporate, Non-US
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	642,500,000
Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	538,600,000
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	418,600,000
Supranational Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 232,600,000