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Note 1 - Summary of Significant Accounting Policies (Details Textual) $ in Thousands | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Jan. 01, 2022 USD ($) | May 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Aug. 08, 2020 USD ($) | Jun. 01, 2014 USD ($)
Number of Unconsolidated Business Trusts Formed to Issue Trust Preferred Securities | 5 |  |  |  |  |  |  |
Financing Receivable, before Allowance for Credit Loss, Total | $ 4,303,758 | $ 3,916,619 |  |  |  |  |  |
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Ending Balance | 0 |  |  |  |  |  |  |
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss | 2,600 | 2,500 |  |  |  |  |  |
Financing Receivable, Unamortized Loan Cost (Fee) | $ 2,400 | 1,000 |  |  |  |  |  |
Interest Income on Commercial and Mortgage Loans Discontinued Period (Day) | 90 days |  |  |  |  |  |  |
Maximum Delinquency Period for Consumer and Credit Card Loans to be Charged Off (Day) | 120 days |  |  |  |  |  |  |
Financing Receivable, Accrued Interest, after Allowance for Credit Loss | $ 16,900 | 12,800 |  |  |  |  |  |
Repossessed Assets | 200 | 0 |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 49,914 | 42,246 | $ 35,363 |  |  | $ 37,967 |  |
Retained Earnings (Accumulated Deficit) | 277,526 | 216,313 |  |  |  |  |  |
Other Expense [Member] |  |  |  |  |  |  |  |
Income (Loss) from Affordable Housing Projects, Equity Method Investments |  | (300) | (200) |  |  |  |  |
Federal Income Tax Expense [Member] |  |  |  |  |  |  |  |
Amortization Method Qualified Affordable Housing Project Investments, Amortization | 500 |  |  |  |  |  |  |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-13 [Member] |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  |  | $ (400) | $ (400) |  |  |  |
Retained Earnings (Accumulated Deficit) |  |  |  | 300 |  |  |  |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-13 [Member] | Other Assets [Member] |  |  |  |  |  |  |  |
Deferred Income Tax Assets, Net |  |  |  | $ 100 |  |  |  |
Not Designated as Hedging Instrument [Member] | Mortgage Loan Derivative [Member] |  |  |  |  |  |  |  |
Derivative Liability | 100 |  |  |  |  |  |  |
Derivative Asset |  | 100 |  |  |  |  |  |
Commercial Loan [Member] |  |  |  |  |  |  |  |
Loan Participation, Amount | 46,700 | $ 33,500 |  |  |  |  |  |
SBA, CARES Act, Paycheck Protection Program [Member] |  |  |  |  |  |  |  |
Number of Loans Originated Under the Paycheck Protection Program |  |  |  |  |  |  | 2,200 |
Financing Receivable, before Allowance for Credit Loss, Total |  |  |  |  |  |  | $ 554,000 |
Financing Receivable, Not Yet Forgiven | 100 |  |  |  |  |  |  |
SBA, CARES Act, Paycheck Protection Program, Round Two [Member] |  |  |  |  |  |  |  |
Number of Loans Originated Under the Paycheck Protection Program |  |  |  |  | 1,200 |  |  |
Financing Receivable, before Allowance for Credit Loss, Total |  |  |  |  | $ 209,000 |  |  |
Financing Receivable, Not Yet Forgiven | $ 200 |  |  |  |  |  |  |
Financing Receivable, Not Yet Forgiven, Number of Loans | 5 |  |  |  |  |  |  |
Firstbank Corporation [Member] |  |  |  |  |  |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets, Total |  |  |  |  |  |  |  | $ 1,500,000
Business Combination Branches Acquired |  |  |  |  |  |  |  | 46

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