Goodwill - Goodwill by Segment (Details) - USD ($) $ in Millions	Dec. 31, 2023	Sep. 30, 2023
Goodwill [Line Items]
Total Goodwill	$ 59.3	$ 59.3
Commercial
Goodwill [Line Items]
Total Goodwill	33.7	33.7
Institutional
Goodwill [Line Items]
Total Goodwill	9.8	9.8
Retail
Goodwill [Line Items]
Total Goodwill	5.8	5.8
Payments
Goodwill [Line Items]
Total Goodwill	$ 10.0	$ 10.0