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Note 16 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | ---
Securities available for sale |  | $ 602,936,000 | $ 592,743,000
Mortgages Held-for-sale, Fair Value Disclosure |  | 3,600,000 | 16,700,000
Servicing Asset at Fair Value, Amount, Ending Balance |  | 17,700,000 | 15,400,000
Fair Value, Inputs, Level 1 [Member] |  |  |
Securities available for sale |  | 0 | 0
Reported Value Measurement [Member] |  |  |
Securities available for sale | [1] | 602,936,000 | 592,743,000
Federal Home Loan Bank stock | [2] | 17,721,000 | 18,002,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Cash and cash equivalents |  | 96,772,000 | 975,160,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Loans, net |  | 3,874,373,000 | 3,418,096,000
Servicing Asset at Fair Value, Amount, Ending Balance |  | 11,837,000 | 12,248,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Mortgages Held-for-sale, Fair Value Disclosure |  | 3,565,000 | 16,117,000
Accrued interest receivable |  | 15,476,000 | 9,311,000
Deposits |  | 3,712,811,000 | 4,083,193,000
Securities sold under agreements to repurchase |  | 194,340,000 | 197,463,000
Federal Home Loan Bank advances |  | 308,263,000 | 374,000,000
Accrued interest payable |  | 3,223,000 | 1,393,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debentures [Member] |  |  |
Subordinated debt |  | 48,958,000 | 48,244,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Notes [Member] |  |  |
Subordinated debt |  | 88,628,000 | 73,646,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member] |  |  |
Derivative Asset, Total |  | 25,697,000 | 4,609,000
Interest rate swaps |  | 25,900,000 | 4,857,000
Estimate of Fair Value Measurement [Member] |  |  |
Securities available for sale | [1] | 602,936,000 | 592,743,000
Federal Home Loan Bank stock | [2] | 17,721,000 | 18,002,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Cash and cash equivalents |  | 96,772,000 | 975,160,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Loans, net |  | 3,800,042,000 | 3,498,345,000
Servicing Asset at Fair Value, Amount, Ending Balance |  | 17,727,000 | 15,445,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Mortgages Held-for-sale, Fair Value Disclosure |  | 3,643,000 | 16,707,000
Accrued interest receivable |  | 15,476,000 | 9,311,000
Deposits |  | 3,379,403,000 | 4,028,249,000
Securities sold under agreements to repurchase |  | 194,340,000 | 197,463,000
Federal Home Loan Bank advances |  | 292,044,000 | 384,927,000
Accrued interest payable |  | 3,223,000 | 1,393,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debentures [Member] |  |  |
Subordinated debt |  | 49,531,000 | 48,284,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Notes [Member] |  |  |
Subordinated debt |  | 75,024,000 | 73,646,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member] |  |  |
Derivative Asset, Total |  | 25,697,000 | 4,609,000
Interest rate swaps |  | $ 25,900,000 | $ 4,857,000
[1] | See Note 17 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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