Goodwill - Schedule of Goodwill Allocated to Operating Segments (Details) - USD ($) $ in Millions	Jun. 30, 2026	Sep. 30, 2025
Goodwill [Line Items]
Total Goodwill	$ 301.8	$ 298.3
Commercial
Goodwill [Line Items]
Total Goodwill	115.0	115.6
Institutional
Goodwill [Line Items]
Total Goodwill	162.6	167.0
Self-Directed/Retail
Goodwill [Line Items]
Total Goodwill	6.1	5.7
Payments
Goodwill [Line Items]
Total Goodwill	$ 18.1	$ 10.0

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details