Corporate Investments and Funds Held For Clients (Corporate Investments And Funds Held For Clients) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Money market securities, cash and other cash equivalents - amortized cost	$ 1,345.0	$ 1,436.3	$ 1,745.0
Amortized Cost	31,140.7	30,113.0
Gross Unrealized  Gains	3.8	9.7
Gross Unrealized Losses	(2,305.1)	(1,731.1)
Fair market value	28,839.4	28,391.6
Total corporate investments and funds held for clients - amortized cost	44,423.2	52,896.0
Total corporate investments and funds held for clients - gross unrealized gains	3.8	9.7
Total corporate investments and funds held for clients - gross unrealized losses	(2,305.1)	(1,731.1)
Total corporate investments and funds held for clients - fair market value	42,121.9	51,174.6
Corporate Investments
Debt Securities, Available-for-sale [Line Items]
Fair market value	16.4	169.1
Funds Held For Clients
Debt Securities, Available-for-sale [Line Items]
Fair market value	28,823.0	28,222.5
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	16,154.2	16,183.1
Gross Unrealized  Gains	1.4	3.9
Gross Unrealized Losses	(1,388.6)	(1,083.0)
Fair market value	14,767.0	15,104.0
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,803.3	5,003.6
Gross Unrealized  Gains	0.1	2.2
Gross Unrealized Losses	(287.7)	(171.1)
Fair market value	6,515.7	4,834.7
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,576.0	1,995.7
Gross Unrealized  Gains	0.3	0.5
Gross Unrealized Losses	(76.8)	(58.8)
Fair market value	1,499.5	1,937.4
Canadian government obligations and Canadian government agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,979.4	2,022.9
Gross Unrealized  Gains	0.0	0.1
Gross Unrealized Losses	(147.3)	(123.5)
Fair market value	1,832.1	1,899.5
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,688.3	1,728.2
Gross Unrealized  Gains	0.0	0.1
Gross Unrealized Losses	(187.1)	(138.2)
Fair market value	1,501.2	1,590.1
Canadian provincial bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	926.4	994.3
Gross Unrealized  Gains	0.2	0.4
Gross Unrealized Losses	(77.8)	(62.7)
Fair market value	848.8	932.0
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	752.5	858.7
Gross Unrealized  Gains	0.0	0.3
Gross Unrealized Losses	(50.3)	(29.9)
Fair market value	702.2	829.1
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,260.6	1,326.5
Gross Unrealized  Gains	1.8	2.2
Gross Unrealized Losses	(89.5)	(63.9)
Fair market value	1,172.9	1,264.8
Money Market Funds
Debt Securities, Available-for-sale [Line Items]
Money market securities, cash and other cash equivalents - amortized cost	13,282.5	22,783.0
Money market securities and other cash equivalents - fair market value	$ 13,282.5	$ 22,783.0