Note 2 - Securities - Debt Securities by Maturity (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Due in 2020, weighted average yield	4.08%
Due in 2020, amortized cost	$ 410,000
Due in 2020, fair value	$ 411,000
Due in 2021 through 2025, weighted average yield	1.63%
Due in 2021 through 2025, amortized cost	$ 70,413,000
Due in 2021 through 2025	$ 71,694,000
Due in 2026 through 2030, weighted average yield	1.89%
Due in 2026 through 2030, amortized cost	$ 138,085,000
Due in 2026 through 2030, fair value	$ 141,743,000
Due in 2031 and beyond, weighted average yield	2.27%
Due in 2031 and beyond, amortized cost	$ 68,172,000
Due in 2031 and beyond, fair value	$ 69,173,000
Weighted average yield	1.95%
Debt Securities, Available-for-sale, Amortized Cost, Total	$ 305,396,000	$ 329,979,000
Debt Securities, Available-for-sale, Total	$ 312,424,000	334,655,000
Collateralized Mortgage Backed Securities [Member]
No single maturity, weighted average yield	2.19%
No single maturity, amortized cost	$ 27,816,000
No single maturity, fair value	28,903,000
Debt Securities, Available-for-sale, Amortized Cost, Total	27,816,000	41,998,000
Debt Securities, Available-for-sale, Total	$ 28,903,000	42,470,000
Other Debt and Equity Securities [Member]
No single maturity, weighted average yield	4.25%
No single maturity, amortized cost	$ 500,000
No single maturity, fair value	500,000
Debt Securities, Available-for-sale, Amortized Cost, Total	500,000	500,000
Debt Securities, Available-for-sale, Total	$ 500,000	$ 500,000