Corporate Investments And Funds Held For Clients (Available-For-Sale Securities That Have Been In An Unrealized Loss Position) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Jun. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	$ (11.0)	$ (8.3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	8,824.6	5,318.3
Fair market value of securities in unrealized loss position less than 12 months	7,790.8	4,242.9
Fair market value of securities in unrealized loss positions greater than 12 months	1,033.8	1,075.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(84.8)	(48.6)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(73.8)	(40.3)
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(3.1)	(2.3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	4,112.3	2,631.6
Fair market value of securities in unrealized loss position less than 12 months	3,898.8	2,403.5
Fair market value of securities in unrealized loss positions greater than 12 months	213.5	228.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(42.5)	(29.6)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(39.4)	(27.3)
U.S. Treasury and direct obligations of U.S. government agencies
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(3.4)	(2.6)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,044.2	1,239.1
Fair market value of securities in unrealized loss position less than 12 months	1,671.0	865.1
Fair market value of securities in unrealized loss positions greater than 12 months	373.2	374.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(21.0)	(9.8)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(17.6)	(7.2)
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(4.1)	(2.9)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,261.0	1,050.4
Fair market value of securities in unrealized loss position less than 12 months	1,841.7	606.8
Fair market value of securities in unrealized loss positions greater than 12 months	419.3	443.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(18.0)	(6.1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(13.9)	(3.2)
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
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	56.9	85.8
Fair market value of securities in unrealized loss position less than 12 months	56.9	85.8
Fair market value of securities in unrealized loss positions greater than 12 months	0.0	0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(0.1)	(0.2)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(0.1)	(0.2)
Canadian provincial bonds
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(0.1)	0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	213.5	111.5
Fair market value of securities in unrealized loss position less than 12 months	203.5	101.5
Fair market value of securities in unrealized loss positions greater than 12 months	10.0	10.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2.1)	(0.8)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2.0)	(0.8)
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(0.1)	(0.2)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	52.2	149.6
Fair market value of securities in unrealized loss position less than 12 months	47.8	143.6
Fair market value of securities in unrealized loss positions greater than 12 months	4.4	6.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(0.4)	(1.4)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(0.3)	(1.2)
Other securities
Schedule of Available-for-sale Securities [Line Items]
Unrealized losses less than 12 months	(0.2)	(0.3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	84.5	50.3
Fair market value of securities in unrealized loss position less than 12 months	71.1	36.6
Fair market value of securities in unrealized loss positions greater than 12 months	13.4	13.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(0.7)	(0.7)
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (0.5)	$ (0.4)