Corporate Investments and Funds Held For Clients (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Mar. 31, 2018		Jun. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Earliest Corporate bond debt maturity date	April 2018
Latest corporate debt maturity date	March 2026
Available-for-sale securities - Fair Market Value	$ 22,502.7	[1]	$ 21,901.1	[2]
Earliest U.S. Treasury maturity date	June 2018
Latest U.S Treasury maturity date	November 2025
Client Fund obligation repayment period	1 year
Client funds obligations	$ 33,943.7		27,189.4
Client funds held in grantor trust	$ 29,879.6
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	$ 2,045.6
Federal Farm Credit Banks
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	596.8
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	153.2
Fixed Rate Credit Card
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	2,050.3
Asset-Backed Auto Loan Receivables
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	1,685.8
Asset-Backed Equipment Lease Receivable
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	454.2
Rate Reduction
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	210.5
Supranational Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	210.2
Commercial Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	256.9
Sovereign Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	112.3
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 $7.3 million and funds held for clients with fair values of $22,495.4 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 $10.8 million and funds held for clients with fair values of $21,890.3 million. All available-for-sale securities were included in Level 2 of the fair value hierarchy.