Corporate Investments and Funds Held for Clients - Schedule of Classification of Corporate Investments on the Consolidated Balance Sheets (Details) - USD ($) $ in Millions		Dec. 31, 2025	Jun. 30, 2025	Dec. 31, 2024
Investments, Debt and Equity Securities [Abstract]
Cash and cash equivalents		$ 2,424.7	$ 3,347.8	$ 2,216.4
Short-term marketable securities	[1]	45.7	4,498.8
Total corporate investments		$ 2,470.4	$ 7,846.6

[1] As of December 31, 2025, $45.7 million of short-term marketable securities and $0.1 million of cash and cash equivalents have been pledged as collateral under the Company's reverse repurchase agreements. As of June 30, 2025, $38.4 million of short-term marketable securities have been pledged as collateral under the Company's reverse repurchase agreements (see Note 10).