Note 10 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($)		Jun. 30, 2022	Dec. 31, 2021
Securities available for sale		$ 603,638,000	$ 592,743,000
Mortgages Held-for-sale, Fair Value Disclosure		13,300,000	16,700,000
Reported Value Measurement [Member]
Securities available for sale	[1]	603,638,000	592,743,000
FHLBI stock	[2]	17,721,000	18,002,000
Mortgages Held-for-sale, Fair Value Disclosure		12,964,000	16,117,000
Estimate of Fair Value Measurement [Member]
Securities available for sale	[1]	603,638,000	592,743,000
FHLBI stock	[2]	17,721,000	18,002,000
Mortgages Held-for-sale, Fair Value Disclosure		13,283,000	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		18,692,000	17,872,000
Cash equivalents		460,413,000	957,288,000
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Cash		18,692,000	17,872,000
Cash equivalents		460,413,000	957,288,000
Fair Value, Inputs, Level 3 [Member] | Reported Value Measurement [Member]
Loans, net		3,687,826,000	3,418,096,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Loans, net		3,632,452,000	3,498,345,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Mortgage servicing rights		12,286,000	12,248,000
Accrued interest receivable		10,884,000	9,311,000
Deposits		3,873,893,000	4,083,193,000
Repurchase agreements		203,339,000	197,463,000
FHLBI advances		362,263,000	374,000,000
Accrued interest payable		2,834,000	1,393,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] | Subordinated Debentures [Member]
Subordinated debt		48,585,000	48,244,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] | Subordinated Notes [Member]
Subordinated debt		88,457,000	73,646,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] | Interest Rate Swap [Member]
Interest rate swaps		17,069,000	4,609,000
Interest rate swaps		17,196,000	4,857,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Mortgage servicing rights		16,547,000	15,445,000
Accrued interest receivable		10,884,000	9,311,000
Deposits		3,573,291,000	4,028,249,000
Repurchase agreements		203,339,000	197,463,000
FHLBI advances		347,018,000	384,927,000
Accrued interest payable		2,834,000	1,393,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Subordinated Debentures [Member]
Subordinated debt		52,820,000	48,284,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Subordinated Notes [Member]
Subordinated debt		83,679,000	73,646,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Interest Rate Swap [Member]
Interest rate swaps		17,069,000	4,609,000
Interest rate swaps		$ 17,196,000	$ 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.