Note 9 - Fair Values of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($)		Sep. 30, 2019	Dec. 31, 2018
Securities available for sale		$ 345,533,000	$ 337,366,000
Reported Value Measurement [Member]
Securities available for sale	[1]	345,533,000	337,366,000
FHLBI stock	[2]	18,002,000	16,022,000
Estimate of Fair Value Measurement [Member]
Securities available for sale	[1]	345,533,000	337,366,000
FHLBI 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		16,077,000	15,656,000
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Cash		16,077,000	15,656,000
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Cash equivalents		212,461,000	59,698,000
Loans held for sale		12,756,000	1,122,000
Mortgage servicing rights		4,385,000	4,436,000
Accrued interest receivable		10,505,000	9,896,000
Deposits		2,767,091,000	2,463,708,000
Repurchase agreements		103,990,000	103,519,000
FHLBI advances		364,000,000	350,000,000
Subordinated debentures		46,710,000	46,199,000
Accrued interest payable		4,295,000	2,249,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Cash equivalents		212,461,000	59,698,000
Loans held for sale		12,756,000	1,122,000
Mortgage servicing rights		7,117,000	8,444,000
Accrued interest receivable		10,505,000	9,896,000
Deposits		2,666,671,000	2,471,617,000
Repurchase agreements		103,990,000	103,519,000
FHLBI advances		376,724,000	348,428,000
Subordinated debentures		46,167,000	46,543,000
Accrued interest payable		4,295,000	2,249,000
Fair Value, Inputs, Level 3 [Member] | Reported Value Measurement [Member]
Loans, net		2,895,843,000	2,729,583,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Loans, net		$ 2,980,135,000	$ 2,711,687,000

[1] See Note 10 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.