Corporate Investments and Funds Held for Clients - Narrative (Details) - USD ($)	6 Months Ended
	Dec. 31, 2023	Jun. 30, 2023
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 30,295,500,000	$ 29,764,900,000
Client fund obligation repayment period	1 year
Client funds obligations	$ 44,002,100,000	38,538,600,000
Client funds held in grantor trust	$ 39,005,900,000	32,758,100,000
Client funds investments with original maturities	ninety
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	552,400,000
Fixed Rate Credit Card
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	377,700,000
Asset-Backed Equipment Lease Receivable
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	157,300,000
Federal Farm Credit Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	990,500,000
Federal Home Loan Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	447,100,000
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	568,800,000	$ 632,500,000
Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	534,300,000
Debt Security, Corporate, Non-US
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	399,500,000
Supranational Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 211,900,000