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Note 4 - Loans and Allowance for Credit Losses (Details Textual) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Jun. 30, 2025 | Dec. 31, 2024 | Dec. 21, 2024 | Jun. 30, 2024 | Dec. 31, 2023
Financing Receivable, Unamortized Loan Cost (Fee) | $ 400 |  | $ 400 |  |  | $ 1,100 |  |  |
Interest Receivable | 21,602 |  | 21,602 |  |  | 20,075 |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 4,102,075 |  | 4,102,075 |  |  | 3,992,534 |  |  |
Off-Balance-Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal) | 1,100 | $ 549 | 3,900 | $ 31 |  |  |  |  |
Debt Securities, Held-to-Maturity, Credit Loss Expense (Reversal) | 2 | 14 | 6 | 76 |  |  |  |  |
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest | 62,127 | 39,142 | 62,127 | 39,142 | $ 59,278 | 59,929 |  | $ 38,332 | $ 35,843
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Period Increase (Decrease) |  |  | $ 2,200 |  |  |  |  |  |
Percentage of Increase in Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest |  |  | 3.70% |  |  |  |  |  |
Loans and Leases Receivables, Impaired, Troubled Debt, Interest Income | 1,500 | 1,900 |  |  |  |  |  |  |
Financing Receivable, Nonaccrual, Interest Income | 0 | 0 |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 0 | 0 |  | 0 |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Modified, Subsequent Default | 0 | $ 0 | $ 0 | $ 0 |  |  |  |  |
Asset Pledged as Collateral [Member] | FHLB Borrowings, Deposits, and Other [Member] |  |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 2,600,000 |  | 2,600,000 |  |  | 2,900,000 |  |  |
Loans Receivable [Member] |  |  |  |  |  |  |  |  |
Interest Receivable | 18,300 |  | 18,300 |  |  | $ 16,400 |  |  |
Non-mortgage Loans [Member] |  |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Transfer out, Allowance for Credit Loss, Expense Reversal |  |  | 78 |  |  |  |  |  |
Metro Phoenix Bank and HMN Financial Inc. [Member] |  |  |  |  |  |  |  |  |
Financing Receivable, Unamortized Purchase Premium (Discount) | $ 47,300 |  | $ 47,300 |  |  |  | $ 70,600 |  |

X
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- Definition Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 22 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147476148/220-40-50-22 + Details
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