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Note 10 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) | Jun. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Securities available for sale |  | $ 608,972,000 | $ 602,936,000
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure |  | 12,200,000 | 3,600,000
Fair Value, Inputs, Level 1 [Member] |  |  |
Securities available for sale |  | 0 | 0
Reported Value Measurement [Member] |  |  |
Securities available for sale | [1] | 608,972,000 | 602,936,000
FHLBI stock | [2] | 21,513,000 | 17,721,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Cash and cash equivalents |  | 207,796,000 | 96,772,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Loans, net |  | 4,007,122,000 | 3,874,373,000
Mortgage servicing rights |  | 11,201,000 | 11,837,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure |  | 11,942,000 | 3,565,000
Accrued interest receivable |  | 16,962,000 | 15,476,000
Deposits |  | 3,756,789,000 | 3,712,811,000
Repurchase agreements |  | 219,457,000 | 194,340,000
FHLBI advances |  | 467,910,000 | 308,263,000
Accrued interest payable |  | 5,652,000 | 3,223,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debentures [Member] |  |  |
Subordinated debt |  | 49,301,000 | 48,958,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Notes [Member] |  |  |
Subordinated debt |  | 88,800,000 | 88,628,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member] |  |  |
Interest rate swaps |  | 26,880,000 | 25,697,000
Interest rate swaps |  | 27,190,000 | 25,900,000
Estimate of Fair Value Measurement [Member] |  |  |
Securities available for sale | [1] | 608,972,000 | 602,936,000
FHLBI stock | [2] | 21,513,000 | 17,721,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Cash and cash equivalents |  | 207,796,000 | 96,772,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Loans, net |  | 3,993,406,000 | 3,800,042,000
Mortgage servicing rights |  | 18,676,000 | 17,727,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure |  | 12,202,000 | 3,643,000
Accrued interest receivable |  | 16,962,000 | 15,476,000
Deposits |  | 3,735,556,000 | 3,379,403,000
Repurchase agreements |  | 219,457,000 | 194,340,000
FHLBI advances |  | 447,929,000 | 292,044,000
Accrued interest payable |  | 5,652,000 | 3,223,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debentures [Member] |  |  |
Subordinated debt |  | 55,991,000 | 49,531,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Notes [Member] |  |  |
Subordinated debt |  | 75,911,000 | 75,024,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member] |  |  |
Interest rate swaps |  | 26,880,000 | 25,697,000
Interest rate swaps |  | $ 27,190,000 | $ 25,900,000
[1] | See Note 11 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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