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Note 16 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Securities available for sale |  | $ 387,347,000 | $ 334,655,000
Servicing Asset at Fair Value, Amount, Ending Balance |  | 10,000,000.0 | 7,400,000
Reported Value Measurement [Member] |  |  |
Securities available for sale | [1] | 387,347,000 | 334,655,000
Federal Home Loan Bank stock | [2] | 18,002,000 | 18,002,000
Securities sold under agreements to repurchase |  | 118,365,000 | 102,675,000
Federal Home Loan Bank advances |  | 394,000,000 | 354,000,000
Estimate of Fair Value Measurement [Member] |  |  |
Securities available for sale | [1] | 387,347,000 | 334,655,000
Federal Home Loan Bank stock | [2] | 18,002,000 | 18,002,000
Securities sold under agreements to repurchase |  | 118,365,000 | 102,675,000
Federal Home Loan Bank advances |  | 410,881,000 | 361,887,000
Fair Value, Inputs, Level 1 [Member] |  |  |
Securities available for sale |  | 0 | 0
Fair Value, Inputs, Level 1 [Member] | Reported Value Measurement [Member] |  |  |
Cash |  | 16,953,000 | 16,430,000
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] |  |  |
Cash |  | 16,953,000 | 16,430,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] |  |  |
Cash equivalents |  | 609,053,000 | 217,301,000
Loans held for sale |  | 22,888,000 | 4,978,000
Servicing Asset at Fair Value, Amount, Ending Balance |  | 8,189,000 | 4,652,000
Accrued interest receivable |  | 10,861,000 | 9,944,000
Deposits |  | 3,411,553,000 | 2,690,384,000
Subordinated debentures |  | 47,563,000 | 46,881,000
Accrued interest payable |  | 2,313,000 | 3,949,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] |  |  |
Cash equivalents |  | 609,053,000 | 217,301,000
Loans held for sale |  | 24,029,000 | 4,978,000
Servicing Asset at Fair Value, Amount, Ending Balance |  | 10,006,000 | 7,375,000
Accrued interest receivable |  | 10,861,000 | 9,944,000
Deposits |  | 3,397,768,000 | 2,600,452,000
Subordinated debentures |  | 47,574,000 | 46,140,000
Accrued interest payable |  | 2,313,000 | 3,949,000
Fair Value, Inputs, Level 3 [Member] | Reported Value Measurement [Member] |  |  |
Loans, net |  | 3,155,503,000 | 2,827,800,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] |  |  |
Loans, net |  | $ 3,294,522,000 | $ 2,887,168,000
[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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