Corporate Investments and Funds Held for Clients - Narrative (Details) - USD ($)	6 Months Ended
	Dec. 31, 2025	Jun. 30, 2025
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 36,318,800,000	$ 33,777,700,000
Client fund obligation repayment period	1 year
Client funds obligations	$ 67,613,700,000	31,343,300,000
Client funds held in grantor trust	$ 61,953,000,000	$ 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	894,900,000
Fixed Rate Credit Card
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	644,300,000
Asset-Backed Securities, Device Payment Plan Agreement Receivables
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	313,700,000
Federal Farm Credit Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	636,100,000
Federal Home Loan Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	137,200,000
Debt Security, Corporate, Non-US
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	648,700,000
Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	549,900,000
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	387,000,000.0
Supranational Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 232,900,000