Note 7 - Fair Value Measurements - Financial Instruments (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Reported Value Measurement [Member]
Cash and due from banks	$ 15,332,000	$ 12,882,000
Interest-bearing deposits	53,381,000	43,491,000
Securities	404,645,000	425,010,000
Restricted securities	1,220,000	1,220,000
Loans held for sale	602,000	72
Loans, net	711,011,000	702,409,000
Accrued interest receivable	5,401,000	5,160,000
Bank-owned life insurance	34,876,000	34,657,000
Deposits	1,060,205,000	1,051,942,000
Accrued interest payable	140,000	89,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and due from banks	15,332,000	12,882,000
Interest-bearing deposits	53,381,000	43,491,000
Securities	0	0
Restricted securities	0	0
Loans held for sale
Loans, net	0	0
Accrued interest receivable	0	0
Bank-owned life insurance	0	0
Deposits	0	0
Accrued interest payable	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Securities	404,645,000	425,010,000
Restricted securities	1,220,000	1,220,000
Loans held for sale	602,000	72
Loans, net	0	0
Accrued interest receivable	5,401,000	5,160,000
Bank-owned life insurance	34,876,000	34,657,000
Deposits	930,351,000	950,143,000
Accrued interest payable	140,000	89,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Securities	0	0
Restricted securities	0	0
Loans held for sale
Loans, net	694,716,000	684,565,000
Accrued interest receivable	0	0
Bank-owned life insurance	0	0
Deposits	109,801,000	101,749,000
Accrued interest payable	$ 0	$ 0