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, 2016	Jun. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (0.8)	$ (40.3)
Fair market value of securities in unrealized loss position less than 12 months	295.9	4,242.9
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.7	8.3
Fair market value of securities in unrealized loss positions greater than 12 months	217.9	1,075.4
Total Gross Unrealized Losses	(1.5)	(48.6)
Total fair market value of securities in unrealized loss position	513.8	5,318.3
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	(0.5)	(27.3)
Fair market value of securities in unrealized loss position less than 12 months	138.0	2,403.5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.1	2.3
Fair market value of securities in unrealized loss positions greater than 12 months	35.1	228.1
Total Gross Unrealized Losses	(0.6)	(29.6)
Total fair market value of securities in unrealized loss position	173.1	2,631.6
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	0.0	(6.9)
Fair market value of securities in unrealized loss position less than 12 months	0.0	836.5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.0	2.6
Fair market value of securities in unrealized loss positions greater than 12 months	0.0	374.0
Total Gross Unrealized Losses	0.0	(9.5)
Total fair market value of securities in unrealized loss position	0.0	1,210.5
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	0.0	(0.3)
Fair market value of securities in unrealized loss position less than 12 months	3.4	28.6
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	1.6	0.0
Total Gross Unrealized Losses	0.0	(0.3)
Total fair market value of securities in unrealized loss position	5.0	28.6
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	(0.1)	(3.2)
Fair market value of securities in unrealized loss position less than 12 months	58.8	606.8
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.2	2.9
Fair market value of securities in unrealized loss positions greater than 12 months	154.8	443.6
Total Gross Unrealized Losses	(0.3)	(6.1)
Total fair market value of securities in unrealized loss position	213.6	1,050.4
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	0.0	(0.2)
Fair market value of securities in unrealized loss position less than 12 months	53.2	85.8
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	0.0	(0.2)
Total fair market value of securities in unrealized loss position	53.2	85.8
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	(0.1)	(0.8)
Fair market value of securities in unrealized loss position less than 12 months	19.1	101.5
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	7.8	10.0
Total Gross Unrealized Losses	(0.1)	(0.8)
Total fair market value of securities in unrealized loss position	26.9	111.5
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	0.0	(1.2)
Fair market value of securities in unrealized loss position less than 12 months	12.9	143.6
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.3	0.2
Fair market value of securities in unrealized loss positions greater than 12 months	10.6	6.0
Total Gross Unrealized Losses	(0.3)	(1.4)
Total fair market value of securities in unrealized loss position	23.5	149.6
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	(0.1)	(0.4)
Fair market value of securities in unrealized loss position less than 12 months	10.5	36.6
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.1	0.3
Fair market value of securities in unrealized loss positions greater than 12 months	8.0	13.7
Total Gross Unrealized Losses	(0.2)	(0.7)
Total fair market value of securities in unrealized loss position	$ 18.5	$ 50.3