Corporate Investments and Funds Held For Clients (Narrative) (Details) - USD ($)	6 Months Ended
	Dec. 31, 2020	Jun. 30, 2020
Debt Securities, Available-for-sale [Line Items]
Fair market value	$ 22,350,500,000	$ 21,576,600,000
Client fund obligation repayment period	1 year
Client funds obligations	$ 36,066,100,000	25,831,600,000
Client funds held in grantor trust	$ 33,706,400,000	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	77.00%
Corporate Investments
Debt Securities, Available-for-sale [Line Items]
Fair market value	$ 10,600,000	13,600,000
Funds Held For Clients
Debt Securities, Available-for-sale [Line Items]
Fair market value	22,339,900,000	21,563,000,000.0
Fair Value, Inputs, Level 1
Debt Securities, Available-for-sale [Line Items]
Fair market value	0
Fair Value, Inputs, Level 3
Debt Securities, Available-for-sale [Line Items]
Fair market value	0
Asset-Backed Auto Loan Receivables
Debt Securities, Available-for-sale [Line Items]
Fair market value	1,478,700,000
Fixed Rate Credit Card
Debt Securities, Available-for-sale [Line Items]
Fair market value	965,800,000
Asset-Backed Equipment Lease Receivable
Debt Securities, Available-for-sale [Line Items]
Fair market value	302,800,000
Rate Reduction
Debt Securities, Available-for-sale [Line Items]
Fair market value	80,800,000
Federal Farm Credit Banks
Debt Securities, Available-for-sale [Line Items]
Fair market value	679,400,000
Federal Home Loan Banks
Debt Securities, Available-for-sale [Line Items]
Fair market value	584,700,000
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair market value	860,400,000	$ 868,200,000
Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Fair market value	560,700,000
Debt Security, Corporate, Non-US
Debt Securities, Available-for-sale [Line Items]
Fair market value	$ 208,300,000