Corporate Investments and Funds Held for Clients - Narrative (Details) - USD ($)	6 Months Ended
	Dec. 31, 2024	Jun. 30, 2024
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 33,019,900,000	$ 31,207,500,000
Client fund obligation repayment period	1 year
Client funds obligations	$ 48,482,200,000	39,503,900,000
Client funds held in grantor trust	$ 43,112,400,000	34,940,000,000
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	751,900,000
Fixed Rate Credit Card
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	480,100,000
Asset-Backed Equipment Lease Receivable
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	167,500,000
Federal Farm Credit Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	960,200,000
Federal Home Loan Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	480,000,000.0
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	453,000,000.0	$ 500,800,000
Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	523,700,000
Debt Security, Corporate, Non-US
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	293,900,000
Supranational Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 213,000,000.0