Note 3 - Securities - Debt Securities by Maturity (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Due in one year or less, weighted average yield	2.04%
Due in one year or less, amortized cost	$ 14,118,000
Due in one year or less, fair value	$ 14,136,000
Due from one to five years, weighted average yield	2.36%
Due from one to five years, amortized cost	$ 52,865,000
Due from one to five years, fair value	$ 53,389,000
Due from five to ten years, weighted average yield	2.66%
Due from five to ten years, amortized cost	$ 105,156,000
Due from five to ten years, fair value	$ 106,960,000
Due after ten years, weighted average yield	3.09%
Due after ten years, amortized cost	$ 115,342,000
Due after ten years, fair value	$ 117,200,000
Weighted average yield	2.76%
Amortized cost	$ 329,979,000	$ 347,795,000
Fair value	$ 334,655,000	337,366,000
Collateralized Mortgage Backed Securities [Member]
No single maturity, weighted average yield	2.76%
No single maturity, amortized cost	$ 41,998,000
No single maturity, fair value	42,470,000
Amortized cost	41,998,000	44,263,000
Fair value	$ 42,470,000	43,658,000
Other Debt and Equity Securities [Member]
No single maturity, weighted average yield	5.88%
No single maturity, amortized cost	$ 500,000
No single maturity, fair value	500,000
Amortized cost	500,000	500,000
Fair value	$ 500,000	$ 500,000