Corporate Investments and Funds Held For Clients (Corporate Investments And Funds Held For Clients) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2021
Debt Securities, Available-for-sale [Line Items]
Money market securities, cash and other cash equivalents - amortized cost	$ 1,207.7	$ 1,436.3	$ 1,602.1
Amortized Cost	31,316.0	30,113.0
Gross Unrealized  Gains	0.4	9.7
Gross Unrealized Losses	(2,555.4)	(1,731.1)
Fair market value	28,761.0	28,391.6
Total corporate investments and funds held for clients - amortized cost	36,892.0	52,896.0
Total corporate investments and funds held for clients - gross unrealized gains	0.4	9.7
Total corporate investments and funds held for clients - gross unrealized losses	(2,555.4)	(1,731.1)
Total corporate investments and funds held for clients - fair market value	34,337.0	51,174.6
Corporate Investments
Debt Securities, Available-for-sale [Line Items]
Fair market value	191.4	169.1
Funds Held For Clients
Debt Securities, Available-for-sale [Line Items]
Fair market value	28,569.6	28,222.5
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	16,156.5	16,183.1
Gross Unrealized  Gains	0.0	3.9
Gross Unrealized Losses	(1,572.8)	(1,083.0)
Fair market value	14,583.7	15,104.0
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,756.6	5,003.6
Gross Unrealized  Gains	0.0	2.2
Gross Unrealized Losses	(303.9)	(171.1)
Fair market value	6,452.7	4,834.7
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,716.7	1,995.7
Gross Unrealized  Gains	0.0	0.5
Gross Unrealized Losses	(81.8)	(58.8)
Fair market value	1,634.9	1,937.4
Canadian government obligations and Canadian government agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,942.7	2,022.9
Gross Unrealized  Gains	0.0	0.1
Gross Unrealized Losses	(149.9)	(123.5)
Fair market value	1,792.8	1,899.5
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,723.2	1,728.2
Gross Unrealized  Gains	0.0	0.1
Gross Unrealized Losses	(199.7)	(138.2)
Fair market value	1,523.5	1,590.1
Canadian provincial bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	940.6	994.3
Gross Unrealized  Gains	0.3	0.4
Gross Unrealized Losses	(81.3)	(62.7)
Fair market value	859.6	932.0
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	807.8	858.7
Gross Unrealized  Gains	0.0	0.3
Gross Unrealized Losses	(54.0)	(29.9)
Fair market value	753.8	829.1
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,271.9	1,326.5
Gross Unrealized  Gains	0.1	2.2
Gross Unrealized Losses	(112.0)	(63.9)
Fair market value	1,160.0	1,264.8
Money Market Funds
Debt Securities, Available-for-sale [Line Items]
Money market securities, cash and other cash equivalents - amortized cost	5,576.0	22,783.0
Money market securities and other cash equivalents - fair market value	$ 5,576.0	$ 22,783.0