Note 10 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands		Mar. 31, 2024	Dec. 31, 2023
Securities available for sale		$ 609,153	$ 617,092
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure		14,600	19,000
Interest Rate Swap [Member]
Interest rate swaps		29,661	27,505
Interest rate swaps		30,036	27,964
Fair Value, Inputs, Level 1 [Member]
Securities available for sale		0	0
Reported Value Measurement [Member]
Securities available for sale	[1]	609,153	617,092
FHLBI stock	[2]	21,513	21,513
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents		237,231	130,533
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net		4,270,368	4,253,844
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure		14,393	18,607
Accrued interest receivable		21,681	19,806
Deposits		4,007,810	3,900,918
Securities sold under agreements to repurchase		228,618	229,734
FHLBI advances		447,083	467,910
Accrued interest payable		10,107	9,012
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debentures [Member]
Subordinated debt		49,815	49,644
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Notes [Member]
Subordinated debt		89,057	88,971
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Interest rate swaps		29,661	27,505
Interest rate swaps		30,036	27,964
Estimate of Fair Value Measurement [Member]
Securities available for sale	[1]	609,153	617,092
FHLBI stock	[2]	21,513	21,513
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents		237,231	130,533
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net		4,243,647	4,191,644
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Loan, Mortgage, Held-for-Sale, Fair Value Disclosure		14,603	19,027
Accrued interest receivable		21,681	19,806
Deposits		3,900,366	3,814,778
Securities sold under agreements to repurchase		228,618	229,734
FHLBI advances		430,397	454,857
Accrued interest payable		10,107	9,012
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debentures [Member]
Subordinated debt		49,824	49,653
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Notes [Member]
Subordinated debt		78,131	77,218
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Interest rate swaps		29,661	27,505
Interest rate swaps		$ 30,036	$ 27,964

[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.