Note 11 - Regulatory Matters - Risk-based Capital and Related Ratios (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Total capital (to risk-weighted assets), Amount	$ 142,005,000	$ 133,406,000
Total capital (to risk-weighted assets), Ratio	0.1544	0.1477
Total capital (to risk-weighted assets), Minimum required for capital adequacy purposes	0.1	0.1
Tier I capital (to risk-weighted assets), Amount	$ 131,394,000	$ 123,753,000
Tier I capital (to risk-weighted assets), Ratio	0.1429	0.137
Tier I capital (to risk-weighted assets), Minimum required for capital adequacy purposes	0.08	0.08
Tier I common equity (to risk-weighted assets), Amount	$ 131,394,000	$ 123,753,000
Tier I common equity (to risk-weighted assets), Ratio	0.1429	0.137
Tier I common equity (to risk-weighted assets), Minimum required for capital adequacy purposes	6.50%	6.50%
Tier I capital (to average assets), Amount	$ 131,394,000	$ 123,753,000
Tier I capital (to average assets), Ratio	0.1109	0.1036
Tier I capital (to average assets), Minimum required for capital adequacy purposes	0.05	0.05
Total risk-weighted assets, Amount	$ 919,761,000	$ 903,172,000
Total average assets, Amount	1,184,972,000	1,194,789,000
Subsidiaries [Member]
Total capital (to risk-weighted assets), Amount	$ 8,000	$ 8,000
Total capital (to risk-weighted assets), Ratio	0.105	0.105
Tier I capital (to risk-weighted assets), Amount	$ 6,000	$ 6,000
Tier I capital (to risk-weighted assets), Ratio	0.085	0.085
Tier I common equity (to risk-weighted assets), Amount	$ 4,500	$ 4,500
Tier I common equity (to risk-weighted assets), Ratio	0.07	0.07
Tier I capital (to average assets), Amount	$ 4,000	$ 4,000
Tier I capital (to average assets), Ratio	0.04	0.04