Note 15 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022
Securities available for sale		$ 617,092	$ 602,936
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure		19,000	3,600
Interest Rate Swap [Member]
Derivative Asset		27,505	26,173
Derivative Liability		27,964	26,377
Fair Value, Inputs, Level 1 [Member]
Securities available for sale		0	0
Reported Value Measurement [Member]
Securities available for sale	[1]	617,092	602,936
Federal Home Loan Bank stock	[2]	21,513	17,721
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents		130,533	96,772
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net		4,253,844	3,874,373
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure		18,607	3,565
Accrued interest receivable		19,806	15,476
Deposits		3,900,918	3,712,811
Securities sold under agreements to repurchase		229,734	194,340
Federal Home Loan Bank advances		467,910	308,263
Accrued interest payable		9,012	3,223
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debentures [Member]
Subordinated debt		49,644	48,958
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Notes [Member]
Subordinated debt		88,971	88,628
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Derivative Asset		27,505	26,173
Derivative Liability		27,964	26,377
Estimate of Fair Value Measurement [Member]
Securities available for sale	[1]	617,092	602,936
Federal Home Loan Bank stock	[2]	21,513	17,721
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents		130,533	96,772
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net		4,191,644	3,800,042
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure		19,027	3,643
Accrued interest receivable		19,806	15,476
Deposits		3,814,778	3,379,403
Securities sold under agreements to repurchase		229,734	194,340
Federal Home Loan Bank advances		454,857	292,044
Accrued interest payable		9,012	3,223
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debentures [Member]
Subordinated debt		49,653	49,531
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Notes [Member]
Subordinated debt		77,218	75,024
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Derivative Asset		27,505	26,173
Derivative Liability		$ 27,964	$ 26,377

[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.