Note 10 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($)		Sep. 30, 2022	Dec. 31, 2021
Securities available for sale		$ 582,999,000	$ 592,743,000
Mortgages Held-for-sale, Fair Value Disclosure		14,700,000	16,700,000
Reported Value Measurement [Member]
Securities available for sale	[1]	582,999,000	592,743,000
FHLBI stock	[2]	17,721,000	18,002,000
Mortgages Held-for-sale, Fair Value Disclosure		14,411,000	16,117,000
Estimate of Fair Value Measurement [Member]
Securities available for sale	[1]	582,999,000	592,743,000
FHLBI stock	[2]	17,721,000	18,002,000
Mortgages Held-for-sale, Fair Value Disclosure		14,709,000	16,707,000
Fair Value, Inputs, Level 1 [Member]
Securities available for sale		0	0
Fair Value, Inputs, Level 1 [Member] | Reported Value Measurement [Member]
Cash		17,016,000	17,872,000
Cash equivalents		266,998,000	957,288,000
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Cash		17,016,000	17,872,000
Cash equivalents		266,998,000	957,288,000
Fair Value, Inputs, Level 3 [Member] | Reported Value Measurement [Member]
Loans, net		3,841,838,000	3,418,096,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Loans, net		3,803,053,000	3,498,345,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Mortgage servicing rights		12,088,000	12,248,000
Accrued interest receivable		13,988,000	9,311,000
Deposits		3,846,085,000	4,083,193,000
Repurchase agreements		198,605,000	197,463,000
FHLBI advances		338,263,000	374,000,000
Accrued interest payable		1,995,000	1,393,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] | Subordinated Debentures [Member]
Subordinated debt		48,787,000	48,244,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] | Subordinated Notes [Member]
Subordinated debt		88,542,000	73,646,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] | Interest Rate Swap [Member]
Interest rate swaps		28,445,000	4,609,000
Interest rate swaps		28,544,000	4,857,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Mortgage servicing rights		17,014,000	15,445,000
Accrued interest receivable		12,988,000	9,311,000
Deposits		3,434,643,000	4,028,249,000
Repurchase agreements		198,605,000	197,463,000
FHLBI advances		318,419,000	384,927,000
Accrued interest payable		1,995,000	1,393,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Subordinated Debentures [Member]
Subordinated debt		49,854,000	48,284,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Subordinated Notes [Member]
Subordinated debt		78,828,000	73,646,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Interest Rate Swap [Member]
Interest rate swaps		28,445,000	4,609,000
Interest rate swaps		$ 28,544,000	$ 4,857,000

[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.