Corporate Investments and Funds Held for Clients - Schedule of Investment of Funds Held for Clients (Details) - USD ($) $ in Millions	Sep. 30, 2025		Jun. 30, 2025	Sep. 30, 2024	[1]
Debt Securities, Available-for-sale [Line Items]
Restricted cash and cash equivalents held to satisfy client funds obligations	$ 1,513.7	[1]	$ 1,706.8	$ 686.6
Total funds held for clients	31,699.9		30,985.7
Current
Debt Securities, Available-for-sale [Line Items]
Restricted short-term and long term marketable securities held to satisfy client funds obligations	2,281.6		3,155.7
Non-current
Debt Securities, Available-for-sale [Line Items]
Restricted short-term and long term marketable securities held to satisfy client funds obligations	$ 27,904.6		$ 26,123.2

[1] See Note 7 for a reconciliation of restricted cash and restricted cash equivalents in funds held for clients on the Consolidated Balance Sheets.