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, 2021	Jun. 30, 2021
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	$ (206.1)	$ (77.6)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	11,884.0	6,331.3
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(23.5)	(0.1)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	741.2	1.9
Total, Gross Unrealized Losses	(229.6)	(77.7)
Total, Fair Market Value	12,625.2	6,333.2
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(120.7)	(38.5)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	7,113.9	3,539.6
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(9.0)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	258.6	0.0
Total, Gross Unrealized Losses	(129.7)	(38.5)
Total, Fair Market Value	7,372.5	3,539.6
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(32.5)	(9.3)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	1,659.3	580.9
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(0.2)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	4.4	0.0
Total, Gross Unrealized Losses	(32.7)	(9.3)
Total, Fair Market Value	1,663.7	580.9
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(6.7)	(0.9)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	409.0	160.9
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(0.1)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	3.1	0.0
Total, Gross Unrealized Losses	(6.8)	(0.9)
Total, Fair Market Value	412.1	160.9
Canadian government obligations and Canadian government agency obligations
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(17.3)	(9.0)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	1,100.3	721.3
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(2.2)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	69.5	0.0
Total, Gross Unrealized Losses	(19.5)	(9.0)
Total, Fair Market Value	1,169.8	721.3
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(11.2)	(9.4)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	681.6	749.7
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(9.5)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	339.9	0.0
Total, Gross Unrealized Losses	(20.7)	(9.4)
Total, Fair Market Value	1,021.5	749.7
Canadian provincial bonds
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(7.9)	(5.3)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	335.2	253.7
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(1.5)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	44.2	0.0
Total, Gross Unrealized Losses	(9.4)	(5.3)
Total, Fair Market Value	379.4	253.7
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(1.7)	0.0
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	115.8	16.7
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	0.0	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	0.0	0.0
Total, Gross Unrealized Losses	(1.7)	0.0
Total, Fair Market Value	115.8	16.7
Other securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(8.1)	(5.2)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	468.9	308.5
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(1.0)	(0.1)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	21.5	1.9
Total, Gross Unrealized Losses	(9.1)	(5.3)
Total, Fair Market Value	$ 490.4	$ 310.4

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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