Summary of Significant Accounting Policies - Loans Receivable and Allowance for Loan Losses and Other Narrative Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) segment bank_location	Dec. 31, 2021 USD ($)
Nature of Operations
Number of banking locations | bank_location	150
Number of reportable business segments | segment	1
Marketable Securities
Securities classified as trading	$ 0.0	$ 0.0
Debt securities held to maturity accrued interest receivable	2.8	2.2
Available for sale accrued interest receivable	2.0	1.9
Loans Receivable
Accrued interest receivable	$ 30.4	21.3
Number of days in delinquency for accrued interest on loans to be considered for reversal, minimum	90 days
Number of days delinquent for loans to be placed on non-accrual status, minimum	90 days
Period of time to return TDRs included in impaired loans to performing status through the fulfilling of contractual terms	180 days
Residential mortgage loans held-for-sale	$ 9.9	$ 25.1
Number of loan segments | segment	7