Corporate Investments and Funds Held For Clients (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Dec. 31, 2019		Jun. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Earliest Corporate bond debt maturity date	January 2020
Latest corporate debt maturity date	November 2029
Fair market value	$ 24,801.1	[1]	$ 24,859.1	[2]
Earliest U.S. treasury maturity date	January 2020
Latest U.S treasury maturity date	December 2029
Client fund obligation repayment period	1 year
Client funds obligations	$ 36,269.9		29,144.5
Client funds held in grantor trust	$ 33,001.5		$ 26,648.0
Client funds investments with original maturities	ninety days or less
Percentage of the available-for-sale securities were rated AAA Or AA	78.00%
Federal Home Loan Banks
Debt Securities, Available-for-sale [Line Items]
Fair market value	$ 1,150.0
Federal Farm Credit Banks
Debt Securities, Available-for-sale [Line Items]
Fair market value	715.6
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Fair market value	90.6
Fixed Rate Credit Card
Debt Securities, Available-for-sale [Line Items]
Fair market value	1,597.4
Asset-Backed Auto Loan Receivables
Debt Securities, Available-for-sale [Line Items]
Fair market value	2,101.3
Asset-Backed Equipment Lease Receivable
Debt Securities, Available-for-sale [Line Items]
Fair market value	418.8
Rate Reduction
Debt Securities, Available-for-sale [Line Items]
Fair market value	121.8
Supranational Bonds
Debt Securities, Available-for-sale [Line Items]
Fair market value	201.9
Commercial Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Fair market value	$ 739.3

[1] Included within available-for-sale securities are corporate investments with fair values of $7.2 million and funds held for clients with fair values of $24,793.9 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 $271.9 million and funds held for clients with fair values of $24,587.2 million. All available-for-sale securities were included in Level 2 of the fair value hierarchy.