Note 3 - Investment Securities (Details Textual)
12 Months Ended
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Proceeds from Sale of Available-for-sale Securities, Debt $ 1,495,000    
Proceeds from Sale and Maturity of Marketable Securities   $ 0 $ 35,377,000
Marketable Securities, Realized Gain (Loss), Excluding Other than Temporary Impairments     $ (33,000)
Security Owned and Pledged as Collateral, Fair Value 73,035,000 58,780,000  
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net $ 0 $ 0  
Collateralized Mortgage Backed Securities [Member]      
Number of Securities In Loss Position 13 15  
Number of Securities 26 26  
US States and Political Subdivisions Debt Securities [Member]      
Number of Securities In Loss Position 33 4  
Number of Securities 44 44  
Asset-backed Securities [Member]      
Number of Securities In Loss Position 2    
Number of Securities 20    
Debt Securities [Member]      
Number of Securities Sold 1    
Available-for-sale Securities, Gross Realized Gains $ 365