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Note 15 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Securities available for sale |  | $ 730,352 | $ 617,092
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure |  | 16,000 | 19,000
Interest Rate Swap [Member] |  |  |
Derivative Asset |  | 26,793 | 27,505
Derivative Liability |  | 27,050 | 27,964
Fair Value, Inputs, Level 1 [Member] |  |  |
Securities available for sale |  | 0 | 0
Reported Value Measurement [Member] |  |  |
Securities available for sale | [1] | 730,352 | 617,092
Federal Home Loan Bank stock | [2] | 21,513 | 21,513
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Cash and cash equivalents |  | 393,010 | 130,533
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Loans, net |  | 4,546,327 | 4,253,844
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure |  | 15,824 | 18,607
Accrued interest receivable |  | 21,401 | 19,806
Deposits |  | 4,698,366 | 3,900,918
Securities sold under agreements to repurchase |  | 121,521 | 229,734
Federal Home Loan Bank advances |  | 387,083 | 467,910
Accrued interest payable |  | 10,201 | 9,012
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debentures [Member] |  |  |
Subordinated debt |  | 50,330 | 49,644
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Notes [Member] |  |  |
Subordinated debt |  | 89,314 | 88,971
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member] |  |  |
Derivative Asset |  | 26,793 | 27,505
Derivative Liability |  | 27,050 | 27,964
Estimate of Fair Value Measurement [Member] |  |  |
Securities available for sale | [1] | 730,352 | 617,092
Federal Home Loan Bank stock | [2] | 21,513 | 21,513
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Cash and cash equivalents |  | 393,010 | 130,533
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Loans, net |  | 4,558,628 | 4,191,644
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure |  | 16,047 | 19,027
Accrued interest receivable |  | 21,401 | 19,806
Deposits |  | 4,541,896 | 3,814,778
Securities sold under agreements to repurchase |  | 121,521 | 229,734
Federal Home Loan Bank advances |  | 374,499 | 454,857
Accrued interest payable |  | 10,201 | 9,012
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debentures [Member] |  |  |
Subordinated debt |  | 50,336 | 49,653
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Notes [Member] |  |  |
Subordinated debt |  | 81,825 | 77,218
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member] |  |  |
Derivative Asset |  | 26,793 | 27,505
Derivative Liability |  | $ 27,050 | $ 27,964
[1] | See Note 16 for a description of the fair value hierarchy as well as a disclosure of levels for classes of financial assets and liabilities.
[2] | It is not practical to determine the fair value of FHLBI stock due to transferability restrictions; therefore, fair value is estimated at carrying amount.

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