Corporate Investments and Funds Held For Clients (Narrative) (Details) - USD ($)	9 Months Ended
	Mar. 31, 2021	Jun. 30, 2020
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 23,271,200,000	$ 21,576,600,000
Client fund obligation repayment period	1 year
Client funds obligations	$ 41,043,000,000.0	25,831,600,000
Client funds held in grantor trust	$ 36,686,900,000	23,740,000,000.0
Client funds investments with original maturities	ninety days or less
Percentage of the available-for-sale securities were rated AAA Or AA	74.00%
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	1,394,600,000
Fixed Rate Credit Card
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	851,400,000
Asset-Backed Equipment Lease Receivable
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	283,000,000.0
Rate Reduction
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	75,500,000
Federal Farm Credit Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	780,800,000
Federal Home Loan Banks
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	556,700,000
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	834,800,000	$ 868,200,000
Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	566,300,000
Debt Security, Corporate, Non-US
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale	$ 236,400,000