Corporate Investments and Funds Held for Clients - Classification of Corporate Investments on the Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Cash and cash equivalents	$ 2,216.4	$ 2,913.4	$ 1,641.3
Short-term marketable securities	0.0	384.0
Long-term marketable securities	0.0	0.0
Total corporate investments	$ 2,216.4	$ 3,297.4

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Sum of the carrying amounts as of the balance sheet date of all investments.

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Amount of investment in marketable security, classified as current.

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