Note 16 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($)		Dec. 31, 2021	Dec. 31, 2020
Securities available for sale		$ 592,743,000	$ 387,347,000
Servicing Asset at Fair Value, Amount, Ending Balance		15,400,000	10,000,000.0
Reported Value Measurement [Member]
Securities available for sale	[1]	592,743,000	387,347,000
Federal Home Loan Bank stock	[2]	18,002,000	18,002,000
Estimate of Fair Value Measurement [Member]
Securities available for sale	[1]	592,743,000	387,347,000
Federal Home Loan Bank stock	[2]	18,002,000	18,002,000
Fair Value, Inputs, Level 1 [Member]
Securities available for sale		0	0
Fair Value, Inputs, Level 1 [Member] | Reported Value Measurement [Member]
Cash		17,872,000	16,953,000
Cash equivalents		957,288,000	609,053,000
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Cash		17,872,000	16,953,000
Cash equivalents		957,288,000	609,053,000
Fair Value, Inputs, Level 3 [Member] | Reported Value Measurement [Member]
Loans, net		3,418,096,000	3,155,503,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Loans, net		3,498,345,000	3,294,522,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Loans held for sale		16,117,000	22,888,000
Servicing Asset at Fair Value, Amount, Ending Balance		12,248,000	8,189,000
Accrued interest receivable		9,311,000	10,861,000
Deposits		4,083,193,000	3,411,553,000
Securities sold under agreements to repurchase		197,463,000	118,365,000
Federal Home Loan Bank advances		374,000,000	394,000,000
Accrued interest payable		1,393,000	2,313,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] | Subordinated Debentures [Member]
Subordinated debt		48,244,000	47,563,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] | Subordinated Notes [Member]
Subordinated debt		73,646,000	0
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] | Interest Rate Swap [Member]
Derivative Asset, Total		4,609,000	1,003,000
Interest rate swaps		4,857,000	1,027,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Loans held for sale		16,707,000	24,029,000
Servicing Asset at Fair Value, Amount, Ending Balance		15,445,000	10,006,000
Accrued interest receivable		9,311,000	10,861,000
Deposits		4,028,249,000	3,397,768,000
Securities sold under agreements to repurchase		197,463,000	118,365,000
Federal Home Loan Bank advances		384,927,000	410,881,000
Accrued interest payable		1,393,000	2,313,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Subordinated Debentures [Member]
Subordinated debt		48,284,000	47,574,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Subordinated Notes [Member]
Subordinated debt		73,646,000	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Interest Rate Swap [Member]
Derivative Asset, Total		4,609,000	1,003,000
Interest rate swaps		$ 4,857,000	$ 1,027,000

[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.