Loans - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) contract	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Net deferred costs	$ 38.1		$ 38.1		$ 35.1
Accrued interest receivable	37.8		37.8		28.2
Interest income from securities with no related allowance	0.4	$ 0.2	$ 0.8	$ 1.4
Loans moved from individually evaluated to collectively evaluated	$ 19.9
Number of loans under trouble debt restructuring | contract			8
Modified in trouble borrower modifications			$ 2.2
Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Remaining fair value adjustment for loans acquired			$ 186.5		$ 97.7
Percentage of fair value adjustment for loans acquired	4.90%		4.90%		4.30%