Corporate Investments And Funds Held For Clients (Available-For-Sale Securities That Have Been In An Unrealized Loss Position) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jun. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (283.4)	$ (73.5)
Fair market value of securities in unrealized loss position less than 12 months	16,606.5	8,915.3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(109.0)	(0.3)
Fair market value of securities in unrealized loss positions greater than 12 months	3,256.8	29.8
Total Gross Unrealized Losses	(392.4)	(73.8)
Total fair market value of securities in unrealized loss position	19,863.3	8,945.1
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(118.2)	(22.0)
Fair market value of securities in unrealized loss position less than 12 months	7,132.9	2,619.9
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(42.7)	0.0
Fair market value of securities in unrealized loss positions greater than 12 months	994.2	7.4
Total Gross Unrealized Losses	(160.9)	(22.0)
Total fair market value of securities in unrealized loss position	8,127.1	2,627.3
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(47.4)	(8.5)
Fair market value of securities in unrealized loss position less than 12 months	3,515.9	1,916.1
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(16.7)	(0.1)
Fair market value of securities in unrealized loss positions greater than 12 months	867.7	11.3
Total Gross Unrealized Losses	(64.1)	(8.6)
Total fair market value of securities in unrealized loss position	4,383.6	1,927.4
U.S. Treasury And Direct Obligations Of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(31.2)	(13.4)
Fair market value of securities in unrealized loss position less than 12 months	2,013.8	1,935.3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(16.5)	0.0
Fair market value of securities in unrealized loss positions greater than 12 months	431.1	0.0
Total Gross Unrealized Losses	(47.7)	(13.4)
Total fair market value of securities in unrealized loss position	2,444.9	1,935.3
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(46.9)	(14.3)
Fair market value of securities in unrealized loss position less than 12 months	1,676.8	1,317.8
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(30.0)	0.0
Fair market value of securities in unrealized loss positions greater than 12 months	864.0	1.0
Total Gross Unrealized Losses	(76.9)	(14.3)
Total fair market value of securities in unrealized loss position	2,540.8	1,318.8
Canadian Government Obligations And Canadian Government Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(20.6)	(11.4)
Fair market value of securities in unrealized loss position less than 12 months	1,020.3	699.6
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.0	0.0
Fair market value of securities in unrealized loss positions greater than 12 months	0.0	0.0
Total Gross Unrealized Losses	(20.6)	(11.4)
Total fair market value of securities in unrealized loss position	1,020.3	699.6
Canadian Provincial Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(6.3)	(1.4)
Fair market value of securities in unrealized loss position less than 12 months	387.7	179.8
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1.1)	0.0
Fair market value of securities in unrealized loss positions greater than 12 months	50.4	0.0
Total Gross Unrealized Losses	(7.4)	(1.4)
Total fair market value of securities in unrealized loss position	438.1	179.8
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3.6)	(1.2)
Fair market value of securities in unrealized loss position less than 12 months	285.8	98.8
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(0.7)	(0.1)
Fair market value of securities in unrealized loss positions greater than 12 months	16.0	1.2
Total Gross Unrealized Losses	(4.3)	(1.3)
Total fair market value of securities in unrealized loss position	301.8	100.0
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(9.2)	(1.3)
Fair market value of securities in unrealized loss position less than 12 months	573.3	148.0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1.3)	(0.1)
Fair market value of securities in unrealized loss positions greater than 12 months	33.4	8.9
Total Gross Unrealized Losses	(10.5)	(1.4)
Total fair market value of securities in unrealized loss position	$ 606.7	$ 156.9