Note 2 - Securities - Debt Securities by Maturity (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Due in 2021, Weighted Average Yield	2.25%
Due in 2021, Amortized Cost	$ 545,000
Due in 2021, Fair Value	$ 547,000
Due in 2022 through 2026, Weighted Average Yield	1.01%
Due in 2022 through 2026, Amortized Cost	$ 187,220,000
Due in 2022 through 2026, Fair Value	$ 188,005,000
Due in 2027 through 2031, Weighted Average Yield	1.56%
Due in 2027 through 2031, Amortized Cost	$ 266,478,000
Due in 2027 through 2031, Fair Value	$ 265,719,000
Due in 2032 and beyond, Weighted Average Yield	1.98%
Due in 2032 and beyond, Amortized Cost	$ 65,896,000
Due in 2032 and beyond, Fair Value	$ 65,340,000
Total available for sale securities, Weighted Average Yield	1.44%
Total available for sale securities, Amortized Cost	$ 559,938,000	$ 380,403,000
Debt Securities, Available-for-sale, Total	$ 559,564,000	387,347,000
Collateralized Mortgage Backed Securities [Member]
No single maturity, weighted average yield	1.76%
No single maturity, amortized cost	$ 39,299,000
No single maturity, fair value	39,453,000
Total available for sale securities, Amortized Cost	39,299,000	23,869,000
Debt Securities, Available-for-sale, Total	$ 39,453,000	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