Corporate Investments and Funds Held For Clients (Corporate Investments And Funds Held For Clients) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Money market securities, cash and other cash equivalents - amortized cost	$ 1,634.2	$ 2,575.2	$ 1,891.5
Amortized Cost	29,319.2	23,869.5
Gross Unrealized  Gains	64.8	579.9
Gross Unrealized Losses	(1,133.2)	(77.7)
Fair market value	28,250.8	24,371.7
Total corporate investments and funds held for clients - amortized cost	61,049.8	37,012.7
Total corporate investments and funds held for clients - gross unrealized gains	64.8	579.9
Total corporate investments and funds held for clients - gross unrealized losses	(1,133.2)	(77.7)
Total corporate investments and funds held for clients - fair market value	59,981.4	37,514.9
Corporate Investments
Debt Securities, Available-for-sale [Line Items]
Fair market value	27.6	33.9
Funds Held For Clients
Debt Securities, Available-for-sale [Line Items]
Fair market value	28,223.2	24,337.8
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,909.4	11,732.3
Gross Unrealized  Gains	38.1	321.9
Gross Unrealized Losses	(685.5)	(38.5)
Fair market value	15,262.0	12,015.7
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,573.2	4,036.9
Gross Unrealized  Gains	8.2	64.8
Gross Unrealized Losses	(134.9)	(9.3)
Fair market value	4,446.5	4,092.4
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,015.1	2,279.8
Gross Unrealized  Gains	6.8	60.9
Gross Unrealized Losses	(36.2)	(0.9)
Fair market value	1,985.7	2,339.8
Canadian government obligations and Canadian government agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,913.0	1,542.3
Gross Unrealized  Gains	0.7	15.0
Gross Unrealized Losses	(84.6)	(9.0)
Fair market value	1,829.1	1,548.3
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,750.5	1,446.3
Gross Unrealized  Gains	0.9	22.5
Gross Unrealized Losses	(91.8)	(9.4)
Fair market value	1,659.6	1,459.4
Canadian provincial bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,006.2	956.3
Gross Unrealized  Gains	1.5	22.7
Gross Unrealized Losses	(40.1)	(5.3)
Fair market value	967.6	973.7
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	874.2	793.4
Gross Unrealized  Gains	4.7	41.2
Gross Unrealized Losses	(16.1)	0.0
Fair market value	862.8	834.6
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,277.6	1,082.2
Gross Unrealized  Gains	3.9	30.9
Gross Unrealized Losses	(44.0)	(5.3)
Fair market value	1,237.5	1,107.8
Money Market Funds
Debt Securities, Available-for-sale [Line Items]
Money market securities, cash and other cash equivalents - amortized cost	31,730.6	13,143.2
Money market securities and other cash equivalents - fair market value	$ 31,730.6	$ 13,143.2