Corporate Investments and Funds Held For Clients - Corporate Investments And Funds Held For Clients (Details) - USD ($) $ in Millions	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2020
Debt Securities, Available-for-sale [Line Items]
Money market securities, cash and other cash equivalents - amortized cost	$ 1,436.3	$ 2,575.2	$ 1,908.5
Amortized Cost	30,113.0	23,869.5
Gross Unrealized  Gains	9.7	579.9
Gross Unrealized Losses	(1,731.1)	(77.7)
Fair market value	28,391.6	24,371.7
Total corporate investments and funds held for clients - amortized cost	52,896.0	37,012.7
Total corporate investments and funds held for clients - gross unrealized gains	9.7	579.9
Total corporate investments and funds held for clients - gross unrealized losses	(1,731.1)	(77.7)
Total corporate investments and funds held for clients - fair market value	51,174.6	37,514.9
Corporate Investments
Debt Securities, Available-for-sale [Line Items]
Fair market value	169.1	33.9
Funds Held For Clients
Debt Securities, Available-for-sale [Line Items]
Fair market value	28,222.5	24,337.8
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	16,183.1	11,732.3
Gross Unrealized  Gains	3.9	321.9
Gross Unrealized Losses	(1,083.0)	(38.5)
Fair market value	15,104.0	12,015.7
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,003.6	4,036.9
Gross Unrealized  Gains	2.2	64.8
Gross Unrealized Losses	(171.1)	(9.3)
Fair market value	4,834.7	4,092.4
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,995.7	2,279.8
Gross Unrealized  Gains	0.5	60.9
Gross Unrealized Losses	(58.8)	(0.9)
Fair market value	1,937.4	2,339.8
Canadian government obligations and Canadian government agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,022.9	1,542.3
Gross Unrealized  Gains	0.1	15.0
Gross Unrealized Losses	(123.5)	(9.0)
Fair market value	1,899.5	1,548.3
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,728.2	1,446.3
Gross Unrealized  Gains	0.1	22.5
Gross Unrealized Losses	(138.2)	(9.4)
Fair market value	1,590.1	1,459.4
Canadian provincial bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	994.3	956.3
Gross Unrealized  Gains	0.4	22.7
Gross Unrealized Losses	(62.7)	(5.3)
Fair market value	932.0	973.7
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	858.7	793.4
Gross Unrealized  Gains	0.3	41.2
Gross Unrealized Losses	(29.9)	0.0
Fair market value	829.1	834.6
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,326.5	1,082.2
Gross Unrealized  Gains	2.2	30.9
Gross Unrealized Losses	(63.9)	(5.3)
Fair market value	1,264.8	1,107.8
Money market securities, cash and other cash equivalents
Debt Securities, Available-for-sale [Line Items]
Money market securities, cash and other cash equivalents - amortized cost	22,783.0	13,143.2
Money market securities and other cash equivalents - fair market value	$ 22,783.0	$ 13,143.2