Note 16 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($)		Dec. 31, 2019	Dec. 31, 2018
Securities available for sale		$ 334,655,000	$ 337,366,000
Servicing Asset at Fair Value, Amount, Ending Balance		7,400,000	8,400,000
Reported Value Measurement [Member]
Securities available for sale	[1]	334,655,000	337,366,000
Federal Home Loan Bank stock	[2]	18,002,000	16,022,000
Estimate of Fair Value Measurement [Member]
Securities available for sale	[1]	334,655,000	337,366,000
Federal Home Loan Bank stock	[2]	18,002,000	16,022,000
Fair Value, Inputs, Level 1 [Member]
Securities available for sale		0	0
Fair Value, Inputs, Level 1 [Member] | Reported Value Measurement [Member]
Cash		16,430,000	15,656,000
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Cash		16,430,000	15,656,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Cash equivalents		217,301,000	59,698,000
Loans held for sale		4,978,000	1,122,000
Servicing Asset at Fair Value, Amount, Ending Balance		4,652,000	4,436,000
Accrued interest receivable		9,944,000	9,896,000
Deposits		2,690,384,000	2,463,708,000
Securities sold under agreements to repurchase		102,675,000	103,519,000
Federal Home Loan Bank advances		354,000,000	350,000,000
Subordinated debentures		46,881,000	46,199,000
Accrued interest payable		3,949,000	2,249,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Cash equivalents		217,301,000	59,698,000
Loans held for sale		4,978,000	1,122,000
Servicing Asset at Fair Value, Amount, Ending Balance		7,375,000	8,444,000
Accrued interest receivable		9,944,000	9,896,000
Deposits		2,600,452,000	2,471,617,000
Securities sold under agreements to repurchase		102,675,000	103,519,000
Federal Home Loan Bank advances		361,887,000	348,428,000
Subordinated debentures		46,140,000	46,543,000
Accrued interest payable		3,949,000	2,249,000
Fair Value, Inputs, Level 3 [Member] | Reported Value Measurement [Member]
Loans, net		2,827,800,000	2,729,583,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Loans, net		$ 2,887,168,000	$ 2,711,687,000

[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.