Note 3 - Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Estimated fair value	$ 159,320,000	$ 171,507,000
Reported Value Measurement [Member]
Cash and cash equivalents	46,942,000	46,686,000
Estimated fair value	159,320,000	171,507,000
Loans, net	616,036,000	562,498,000
FHLB stock	3,517,000	3,027,000
Accrued interest receivable	3,398,000	3,345,000
Deposits	747,324,000	726,565,000
Repurchase agreements	16,013,000	13,058,000
Junior subordinated deferrable interest debentures	10,310,000	10,310,000
Accrued interest payable	96,000	88,000
Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	46,942,000	46,686,000
Estimated fair value	159,320,000	171,507,000
Loans, net	626,795,000	580,396,000
Accrued interest receivable	3,398,000	3,345,000
Deposits	747,332,000	726,649,000
Repurchase agreements	16,013,000	13,058,000
Junior subordinated deferrable interest debentures	7,661,000	8,092,000
Accrued interest payable	96,000	88,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	46,942,000	46,686,000
Accrued interest receivable	15,000	22,000
Deposits	709,130,000	669,599,000
Accrued interest payable	13,000	11,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Estimated fair value	159,320,000	171,507,000
Accrued interest receivable	574,000	685,000
Deposits	38,202,000	57,050,000
Repurchase agreements	16,013,000	13,058,000
Accrued interest payable	60,000	52,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net	626,795,000	580,396,000
Accrued interest receivable	2,809,000	2,638,000
Junior subordinated deferrable interest debentures	7,661,000	8,092,000
Accrued interest payable	$ 23,000	$ 25,000