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, 2020	Jun. 30, 2020
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	$ (2.2)	$ (0.7)
Fair market value of securities in unrealized loss position less than 12 months	887.2	63.0
Unrealized losses greater than 12 months	0.0	0.0
Fair market value of securities in unrealized loss positions greater than 12 months	1.4	1.5
Total gross unrealized losses	(2.2)	(0.7)
Total fair market value	888.6	64.5
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(0.9)	0.0
Fair market value of securities in unrealized loss position less than 12 months	379.3	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	(0.9)	0.0
Total fair market value	379.3	0.0
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	0.0	(0.5)
Fair market value of securities in unrealized loss position less than 12 months	3.2	43.9
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	(0.5)
Total fair market value	3.2	43.9
U.S. government agency securities
Debt Securities, Available-for-sale [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	14.1	2.0
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	14.1	2.0
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(0.9)	0.0
Fair market value of securities in unrealized loss position less than 12 months	348.6	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	(0.9)	0.0
Total fair market value	348.6	0.0
Canadian government obligations and Canadian government agency obligations
Debt Securities, Available-for-sale [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	68.1	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	68.1	0.0
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [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	0.0	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	1.4	1.5
Total gross unrealized losses	0.0	0.0
Total fair market value	1.4	1.5
Canadian provincial bonds
Debt Securities, Available-for-sale [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	45.7	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	45.7	0.0
Other securities
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(0.1)	(0.2)
Fair market value of securities in unrealized loss position less than 12 months	28.2	17.1
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)	(0.2)
Total fair market value	$ 28.2	$ 17.1

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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