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Note 1 - Summary of Significant Accounting Policies (Details Textual) | 12 Months Ended |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2022 USD ($) | Jan. 01, 2022 USD ($) | Dec. 31, 2021 USD ($) | May 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Aug. 08, 2020 USD ($) | Dec. 31, 2019 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 | $ 3,916,619,000 |  | $ 3,453,459,000 |  |  |  |  |
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Ending Balance | 0 |  |  |  |  |  |  |
Financing Receivable, Unamortized Loan Cost (Fee) | $ (1,000,000.0) |  | 2,500,000 |  |  |  |  |
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, Allowance for Credit Loss, Ending Balance | $ 42,246,000 |  | 35,363,000 |  | $ 37,967,000 |  | $ 23,889,000 |
Retained Earnings (Accumulated Deficit), Total | 216,313,000 |  | 174,536,000 |  |  |  |  |
Financing Receivable, Allowance for Credit Loss, Allowance Reduction | (900,000) |  |  |  |  |  |  |
Repossessed Assets, Total | $ 0 |  | 0 |  |  |  |  |
Core Deposits [Member] |  |  |  |  |  |  |  |
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life (Year) | 10 years |  |  |  |  |  |  |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-13 [Member] |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | $ (400,000) |  |  |  |  |  |  |
Retained Earnings (Accumulated Deficit), Total |  | $ 300,000 |  |  |  |  |  |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-13 [Member] | Other Assets [Member] |  |  |  |  |  |  |  |
Deferred Income Tax Assets, Net |  | $ 100,000 |  |  |  |  |  |
Not Designated as Hedging Instrument [Member] | Mortgage Loan Derivative [Member] |  |  |  |  |  |  |  |
Derivative Asset, Total | 100,000 |  | 300,000 |  |  |  |  |
Commercial Loan [Member] |  |  |  |  |  |  |  |
Loan Participation, Amount | $ 33,500,000 |  | $ 24,200,000 |  |  |  |  |
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 |  |  |  |  |  | $ 554,000,000 |  |
Financing Receivable, Not Yet Forgiven, Number of Loans | 5 |  |  |  |  |  |  |
Financing Receivable, Not Yet Forgiven | $ 500,000 |  |  |  |  |  |  |
Amortization of Deferred Loan Origination Fees, Net | $ 100,000 |  |  |  |  |  |  |
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 |  |  |  | $ 209,000,000 |  |  |  |
Financing Receivable, Not Yet Forgiven, Number of Loans | 6 |  |  |  |  |  |  |
Financing Receivable, Not Yet Forgiven | $ 400,000 |  |  |  |  |  |  |
Amortization of Deferred Loan Origination Fees, Net | $ 1,000,000.0 |  |  |  |  |  |  |
Firstbank Corporation [Member] |  |  |  |  |  |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets, Total |  |  |  |  |  |  |  | $ 1,500,000,000
Business Combination Branches Acquired |  |  |  |  |  |  |  | 46

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