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, 2022	Jun. 30, 2022
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	$ (899.3)	$ (1,305.8)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	17,527.4	20,798.8
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(1,405.8)	(425.3)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	11,063.9	4,005.8
Total, Gross Unrealized Losses	(2,305.1)	(1,731.1)
Total, Fair Market Value	28,591.3	24,804.6
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(552.1)	(824.0)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	8,221.3	11,525.4
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(836.5)	(259.0)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	6,457.6	2,356.7
Total, Gross Unrealized Losses	(1,388.6)	(1,083.0)
Total, Fair Market Value	14,678.9	13,882.1
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(116.0)	(126.4)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	5,008.0	2,919.6
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(171.7)	(44.7)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	1,495.8	464.6
Total, Gross Unrealized Losses	(287.7)	(171.1)
Total, Fair Market Value	6,503.8	3,384.2
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(30.4)	(52.6)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	1,091.4	1,444.9
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(46.4)	(6.2)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	371.0	59.9
Total, Gross Unrealized Losses	(76.8)	(58.8)
Total, Fair Market Value	1,462.4	1,504.8
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	(39.0)	(110.0)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	808.8	1,782.6
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(108.3)	(13.5)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	1,019.9	113.3
Total, Gross Unrealized Losses	(147.3)	(123.5)
Total, Fair Market Value	1,828.7	1,895.9
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(61.0)	(75.3)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	586.0	859.3
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(126.1)	(62.9)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	915.2	695.6
Total, Gross Unrealized Losses	(187.1)	(138.2)
Total, Fair Market Value	1,501.2	1,554.9
Canadian provincial bonds
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(29.6)	(45.4)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	503.0	726.9
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(48.2)	(17.3)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	324.1	133.2
Total, Gross Unrealized Losses	(77.8)	(62.7)
Total, Fair Market Value	827.1	860.1
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(39.3)	(29.5)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	610.4	802.8
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(11.0)	(0.4)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	91.8	4.3
Total, Gross Unrealized Losses	(50.3)	(29.9)
Total, Fair Market Value	702.2	807.1
Other securities
Debt Securities, Available-for-sale [Line Items]
Securities in Unrealized Loss Position Less Than 12 Months, Gross Unrealized Losses	(31.9)	(42.6)
Securities in Unrealized Loss Position Less Than 12 Months, Fair Market Value	698.5	737.3
Securities in Unrealized Loss Position Greater Than 12 Months, Gross Unrealized Losses	(57.6)	(21.3)
Securities in Unrealized Loss Position Greater Than 12 Months, Fair Market Value	388.5	178.2
Total, Gross Unrealized Losses	(89.5)	(63.9)
Total, Fair Market Value	$ 1,087.0	$ 915.5