Corporate Investments And Funds Held For Clients (Available-For-Sale Securities That Have Been In An Unrealized Loss Position) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Jun. 30, 2016
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	$ (2.6)	$ (0.8)
Fair market value of securities in unrealized loss position less than 12 months	974.2	295.9
Unrealized losses greater than 12 months	(0.4)	(0.7)
Fair market value of securities in unrealized loss positions greater than 12 months	194.7	217.9
Total gross unrealized losses	(3.0)	(1.5)
Total fair market value	1,168.9	513.8
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(1.7)	(0.5)
Fair market value of securities in unrealized loss position less than 12 months	474.8	138.0
Unrealized losses greater than 12 months	0.0	(0.1)
Fair market value of securities in unrealized loss positions greater than 12 months	41.4	35.1
Total gross unrealized losses	(1.7)	(0.6)
Total fair market value	516.2	173.1
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(0.1)	0.0
Fair market value of securities in unrealized loss position less than 12 months	94.8	0.0
Unrealized losses greater than 12 months	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	(0.1)	0.0
Total fair market value	94.8	0.0
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(0.3)	(0.1)
Fair market value of securities in unrealized loss position less than 12 months	294.2	58.8
Unrealized losses greater than 12 months	(0.1)	(0.2)
Fair market value of securities in unrealized loss positions greater than 12 months	132.6	154.8
Total gross unrealized losses	(0.4)	(0.3)
Total fair market value	426.8	213.6
Canadian government obligations and Canadian government agency obligations
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	0.0	0.0
Fair market value of securities in unrealized loss position less than 12 months	7.6	53.2
Unrealized losses greater than 12 months	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	0.0
Total fair market value	7.6	53.2
Canadian provincial bonds
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	0.0	(0.1)
Fair market value of securities in unrealized loss position less than 12 months	27.0	19.1
Unrealized losses greater than 12 months	0.0	0.0
Fair market value of securities in unrealized loss positions greater than 12 months	7.7	7.8
Total gross unrealized losses	0.0	(0.1)
Total fair market value	34.7	26.9
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	0.0	0.0
Fair market value of securities in unrealized loss position less than 12 months	2.1	3.4
Unrealized losses greater than 12 months	0.0	0.0
Fair market value of securities in unrealized loss positions greater than 12 months	0.0	1.6
Total gross unrealized losses	0.0	0.0
Total fair market value	2.1	5.0
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(0.4)	0.0
Fair market value of securities in unrealized loss position less than 12 months	61.5	12.9
Unrealized losses greater than 12 months	(0.2)	(0.3)
Fair market value of securities in unrealized loss positions greater than 12 months	8.1	10.6
Total gross unrealized losses	(0.6)	(0.3)
Total fair market value	69.6	23.5
Other securities
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(0.1)	(0.1)
Fair market value of securities in unrealized loss position less than 12 months	12.2	10.5
Unrealized losses greater than 12 months	(0.1)	(0.1)
Fair market value of securities in unrealized loss positions greater than 12 months	4.9	8.0
Total gross unrealized losses	(0.2)	(0.2)
Total fair market value	$ 17.1	$ 18.5