v3.26.3
Note 1 - Significant Accounting Policies (Details Textual)
$ in Thousands
 3 Months Ended 9 Months Ended
Dec. 31, 2025
USD ($)
Sep. 30, 2026
USD ($)
shares
Sep. 30, 2025
USD ($)
shares
Sep. 30, 2026
USD ($)
shares
Sep. 30, 2025
USD ($)
shares
Number of Unconsolidated Business Trusts Formed to Issue Trust Preferred Securities   5   5  
Debt Securities, Available-for-Sale, Allowance for Credit Loss $ 0 $ 0   $ 0  
Financing Receivable, Unamortized Loan Cost (Fee) 1,300 900   900  
Investment Income, Net, Amortization of Discount and Premium       $ 400  
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  
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure 17,300 22,500   $ 22,500  
Financing Receivable, Credit Loss, Expense (Reversal)   700 $ 200 (2,900) $ 3,900
Financing Receivable, Accrued Interest, after Allowance for Credit Loss 17,500 18,300   18,300  
Continuing Involvement with Transferred Financial Assets, Principal Amount Outstanding 1,690,000 1,730,000   1,730,000  
Servicing Asset at Amortized Cost 13,600 13,800   13,800  
Servicing Asset at Fair Value, Amount 21,400 $ 23,100   $ 23,100  
Restricted Stock [Member]          
Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights (in shares) | shares   255,000 277,000 255,000 277,000
Eastern Michigan Financial Corp. [Member]          
Business Combination, Recognized Asset Acquired, Asset Including Goodwill $ 572,000        
Business Combination Branches Acquired 11        
Business Combination, Recognized Asset Acquired, Financing Receivable, Unamortized Purchase Premium (Discount) $ (1,500)        
Goodwill, Acquired During Period $ 24,200