Corporate Investments and Funds Held For Clients (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Mar. 31, 2019		Jun. 30, 2018
Schedule of Available-for-sale Securities [Line Items]
Earliest Corporate bond debt maturity date	April 2019
Latest corporate debt maturity date	November 2028
Available-for-sale securities - Fair Market Value	$ 23,703.4	[1]	$ 22,776.2	[2]
Earliest U.S. Treasury maturity date	May 2019
Latest U.S Treasury maturity date	January 2029
Client Fund obligation repayment period	1 year
Client funds obligations	$ 36,055.6		27,493.5
Client funds held in grantor trust	$ 32,528.8		24,242.9
Client funds investments with original maturities	ninety days or less
Percentage of the available-for-sale securities were rated AAA Or AA	80.00%
Federal Home Loan Banks
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	$ 1,798.0
Federal Farm Credit Banks
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	656.1
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	117.9
Fixed Rate Credit Card
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	1,957.9
Asset-Backed Auto Loan Receivables
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	1,940.0
Asset-Backed Equipment Lease Receivable
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	489.5
Rate Reduction
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	175.8
Supranational Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	198.9
Commercial Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	398.5
Sovereign Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	77.8
Level 1
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	0.0		0.0
Level 3
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	$ 0.0		$ 0.0

[1] Included within available-for-sale securities are corporate investments with fair values of $10.5 million and funds held for clients with fair values of $23,692.9 million. All available-for-sale securities were included in Level 2 of the fair value hierarchy.

[2] Included within available-for-sale securities are corporate investments with fair values of $10.5 million and funds held for clients with fair values of $22,765.7 million. All available-for-sale securities were included in Level 2 of the fair value hierarchy.