Note 2 - Securities - Debt Securities by Maturity (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Due in 2021, Weighted Average Yield	2.53%
Due in 2021, Amortized Cost	$ 5,414,000
Due in 2021, Fair Value	$ 5,425,000
Due in 2022 through 2026, Weighted Average Yield	1.16%
Due in 2022 through 2026, Amortized Cost	$ 142,876,000
Due in 2022 through 2026, Fair Value	$ 143,569,000
Due in 2027 through 2031, Weighted Average Yield	1.63%
Due in 2027 through 2031, Amortized Cost	$ 197,842,000
Due in 2027 through 2031, Fair Value	$ 195,378,000
Due in 2032 and beyond, Weighted Average Yield	2.02%
Due in 2032 and beyond, Amortized Cost	$ 54,638,000
Due in 2032 and beyond, Fair Value	$ 53,577,000
Total available for sale securities, Weighted Average Yield	1.55%
Total available for sale securities, Amortized Cost	$ 436,481,000	$ 380,403,000
Debt Securities, Available-for-sale, Total	$ 434,257,000	387,347,000
Collateralized Mortgage Backed Securities [Member]
No single maturity, weighted average yield	1.83%
No single maturity, amortized cost	$ 35,211,000
No single maturity, fair value	35,808,000
Total available for sale securities, Amortized Cost	35,211,000	23,869,000
Debt Securities, Available-for-sale, Total	$ 35,808,000	24,890,000
Other Debt and Equity Securities [Member]
No single maturity, weighted average yield	3.75%
No single maturity, amortized cost	$ 500,000
No single maturity, fair value	500,000
Total available for sale securities, Amortized Cost	500,000	500,000
Debt Securities, Available-for-sale, Total	$ 500,000	$ 500,000