Note 8 - Fair Value of Financial Instruments - Assets and Liabilities Measured On a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Securities available for sale	$ 304,122	$ 309,516
Fair Value, Inputs, Level 1 [Member]
Securities available for sale
Fair Value, Inputs, Level 2 [Member]
Securities available for sale	296,083	301,132
Fair Value, Inputs, Level 3 [Member]
Securities available for sale	8,039	8,384
US Government Agencies Debt Securities [Member]
Securities available for sale	19,515	17,439
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	19,515	17,439
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale
Corporate Debt Securities [Member]
Securities available for sale	12,912	12,692
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	12,912	12,692
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale
Collateralized Mortgage Backed Securities [Member]
Securities available for sale	166,864	165,618
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	166,864	165,618
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale
US States and Political Subdivisions Debt Securities [Member]
Securities available for sale	104,831	113,767
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	96,792	105,383
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale	$ 8,039	$ 8,384