Note 9 - Fair Value Measurement - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Estimated fair value	$ 159,247	$ 159,320
Reported Value Measurement [Member]
Cash and cash equivalents	58,058	46,942
Estimated fair value	159,247	159,320
Loans, net	619,487	616,036
FHLB stock	3,517	3,517
Accrued interest receivable	2,995	3,398
Deposits	762,886	747,324
Repurchase agreements	8,383	16,013
Junior subordinated deferrable interest debentures	10,310	10,310
Accrued interest payable	91	96
Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	58,058	46,942
Estimated fair value	159,247	159,320
Loans, net	662,368	626,795
Accrued interest receivable	2,995	3,398
Deposits	764,400	747,332
Repurchase agreements	8,383	16,013
Junior subordinated deferrable interest debentures	7,080	7,661
Accrued interest payable	91	96
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	58,058	46,942
Accrued interest receivable	1	15
Deposits	725,158	709,130
Accrued interest payable	11	13
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Estimated fair value	159,247	159,320
Accrued interest receivable	559	574
Deposits	39,242	38,202
Repurchase agreements	8,383	16,013
Accrued interest payable	60	60
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net	662,368	626,795
Accrued interest receivable	2,435	2,809
Junior subordinated deferrable interest debentures	7,080	7,661
Accrued interest payable	$ 20	$ 23