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, 2022	Jun. 30, 2021
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	$ (1,305.8)	$ (77.6)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	20,798.8	6,331.3
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(425.3)	(0.1)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	4,005.8	1.9
Total, Gross Unrealized Losses	(1,731.1)	(77.7)
Total, Fair Market Value	24,804.6	6,333.2
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(824.0)	(38.5)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	11,525.4	3,539.6
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(259.0)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	2,356.7	0.0
Total, Gross Unrealized Losses	(1,083.0)	(38.5)
Total, Fair Market Value	13,882.1	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	(126.4)	(9.3)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	2,919.6	580.9
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(44.7)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	464.6	0.0
Total, Gross Unrealized Losses	(171.1)	(9.3)
Total, Fair Market Value	3,384.2	580.9
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(52.6)	(0.9)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	1,444.9	160.9
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(6.2)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	59.9	0.0
Total, Gross Unrealized Losses	(58.8)	(0.9)
Total, Fair Market Value	1,504.8	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	(110.0)	(9.0)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	1,782.6	721.3
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(13.5)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	113.3	0.0
Total, Gross Unrealized Losses	(123.5)	(9.0)
Total, Fair Market Value	1,895.9	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	(75.3)	(9.4)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	859.3	749.7
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(62.9)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	695.6	0.0
Total, Gross Unrealized Losses	(138.2)	(9.4)
Total, Fair Market Value	1,554.9	749.7
Canadian provincial bonds
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(45.4)	(5.3)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	726.9	253.7
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(17.3)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	133.2	0.0
Total, Gross Unrealized Losses	(62.7)	(5.3)
Total, Fair Market Value	860.1	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	(29.5)	0.0
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	802.8	16.7
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(0.4)	0.0
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	4.3	0.0
Total, Gross Unrealized Losses	(29.9)	0.0
Total, Fair Market Value	807.1	16.7
Other securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(42.6)	(5.2)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	737.3	308.5
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(21.3)	(0.1)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	178.2	1.9
Total, Gross Unrealized Losses	(63.9)	(5.3)
Total, Fair Market Value	$ 915.5	$ 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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