Corporate Investments and Funds Held For Clients (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2017		Jun. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Earliest Corporate bond debt maturity date	October 2017
Latest corporate debt maturity date	March 2026
Available-for-sale securities - Fair Market Value	$ 22,106.6	[1]	$ 21,901.1	[2]
Earliest U.S. Treasury maturity date	December 2017
Latest U.S Treasury maturity date	September 2025
Length of shortest cash flow of residential mortgages used as collateral for companies mortgage backed securities (in years)	15 years
Length of longest cash flow of residential mortgages used as collateral for company's mortgage backed securities (in years)	30 years
Client Fund obligation repayment period	1 year
Client funds obligations	$ 25,596.6		27,189.4
Client funds investments with original maturities	ninety days or less
Percentage of the available-for-sale securities were rated AAA Or AA	79.00%
Federal Home Loan Banks
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	$ 2,423.6
Federal Farm Credit Banks
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	573.4
Fixed Rate Credit Card
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	2,133.2
Asset-Backed Auto Loan Receivables
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	1,412.0
Asset-Backed Equipment Lease Receivable
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	434.4
Rate Reduction
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	232.3
Supranational Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	111.5
Commercial Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	102.4
Sovereign Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	130.1
Residential Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities - Fair Market Value	91.6
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 $140.0 million and funds held for clients with fair values of $21,966.6 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.