Note 3 - Securities - Debt Securities by Maturity (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Due in one year or less, weighted average yield	1.89%
Due in one year or less, amortized cost	$ 27,286,000
Due in one year or less, fair value	$ 27,223,000
Due from one to five years, weighted average yield	2.32%
Due from one to five years, amortized cost	$ 50,143,000
Due from one to five years, fair value	$ 49,585,000
Due from five to ten years, weighted average yield	2.62%
Due from five to ten years, amortized cost	$ 108,765,000
Due from five to ten years, fair value	$ 104,945,000
Due after ten years, weighted average yield	3.13%
Due after ten years, amortized cost	$ 116,838,000
Due after ten years, fair value	$ 111,455,000
Weighted average yield	2.71%
Amortized cost	$ 347,795,000	$ 341,948,000
Fair value	$ 337,366,000	335,744,000
Collateralized Mortgage Backed Securities [Member]
No single maturity, weighted average yield	2.76%
No single maturity, amortized cost	$ 44,263,000
No single maturity, fair value	43,658,000
Amortized cost	44,263,000	38,967,000
Fair value	$ 43,658,000	38,792,000
Other Debt and Equity Securities [Member]
No single maturity, weighted average yield	5.37%
No single maturity, amortized cost	$ 500,000
No single maturity, fair value	500,000
Amortized cost	500,000	2,010,000
Fair value	$ 500,000	$ 1,981,000