Corporate Investments and Funds Held For Clients (Corporate Investments And Funds Held For Clients) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Money market securities, cash and other cash equivalents - amortized cost	$ 2,575.2	$ 1,908.5	$ 1,949.2
Amortized Cost	23,869.5	20,699.8
Gross Unrealized  Gains	579.9	877.5
Gross Unrealized Losses	(77.7)	(0.7)
Fair market value	24,371.7	21,576.6
Total corporate investments and funds held for clients - amortized cost	37,012.7	27,753.4
Total corporate investments and funds held for clients - gross unrealized gains	579.9	877.5
Total corporate investments and funds held for clients - gross unrealized losses	(77.7)	(0.7)
Total corporate investments and funds held for clients - fair market value	37,514.9	28,630.2
Corporate Investments
Debt Securities, Available-for-sale [Line Items]
Fair market value	33.9	13.6
Funds Held For Clients
Debt Securities, Available-for-sale [Line Items]
Fair market value	24,337.8	21,563.0
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,732.3	9,188.7
Gross Unrealized  Gains	321.9	473.4
Gross Unrealized Losses	(38.5)	0.0
Fair market value	12,015.7	9,662.1
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,036.9	3,580.6
Gross Unrealized  Gains	64.8	120.8
Gross Unrealized Losses	(9.3)	0.0
Fair market value	4,092.4	3,701.4
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,279.8	3,274.6
Gross Unrealized  Gains	60.9	96.0
Gross Unrealized Losses	(0.9)	(0.5)
Fair market value	2,339.8	3,370.1
Canadian government obligations and Canadian government agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,542.3	1,018.7
Gross Unrealized  Gains	15.0	23.1
Gross Unrealized Losses	(9.0)	0.0
Fair market value	1,548.3	1,041.8
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,446.3	1,128.2
Gross Unrealized  Gains	22.5	35.6
Gross Unrealized Losses	(9.4)	0.0
Fair market value	1,459.4	1,163.8
Canadian provincial bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	956.3	676.6
Gross Unrealized  Gains	22.7	33.6
Gross Unrealized Losses	(5.3)	0.0
Fair market value	973.7	710.2
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	793.4	814.3
Gross Unrealized  Gains	41.2	53.9
Gross Unrealized Losses	0.0	0.0
Fair market value	834.6	868.2
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,082.2	1,018.1
Gross Unrealized  Gains	30.9	41.1
Gross Unrealized Losses	(5.3)	(0.2)
Fair market value	1,107.8	1,059.0
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	13,143.2	7,053.6
Money market securities and other cash equivalents - fair market value	$ 13,143.2	$ 7,053.6