Note 10 - Fair Value Measurement - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Estimated fair value	$ 173,227	$ 171,507
Reported Value Measurement [Member]
Cash and cash equivalents	44,753	46,686
Estimated fair value	173,227	171,507
Loans, net	569,778	562,498
FHLB stock	3,027	3,027
Accrued interest receivable	3,065	3,345
Deposits	730,923	726,565
Repurchase agreements	8,910	13,058
Junior subordinated deferrable interest debentures	10,310	10,310
Accrued interest payable	94	88
Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	44,753	46,686
Estimated fair value	173,227	171,507
Loans, net	598,785	580,396
Accrued interest receivable	3,065	3,345
Deposits	731,052	726,649
Repurchase agreements	8,910	13,058
Junior subordinated deferrable interest debentures	7,925	8,092
Accrued interest payable	94	88
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	44,753	46,686
Accrued interest receivable	5	22
Deposits	676,306	669,599
Accrued interest payable	12	11
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Estimated fair value	173,227	171,507
Accrued interest receivable	654	685
Deposits	54,746	57,050
Repurchase agreements	8,910	13,058
Accrued interest payable	57	52
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net	598,785	580,396
Accrued interest receivable	2,406	2,638
Junior subordinated deferrable interest debentures	7,925	8,092
Accrued interest payable	$ 25	$ 25