Note 18 - Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities	$ 196,806	$ 188,476
Fair Value, Inputs, Level 1 [Member]
Available-for-sale Securities	0	0
Fair Value, Inputs, Level 2 [Member]
Available-for-sale Securities	196,806	188,476
Fair Value, Inputs, Level 3 [Member]
Available-for-sale Securities	0	0
US Treasury and Government [Member]
Available-for-sale Securities	2,963	5,631
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale Securities	0	0
US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale Securities	2,963	5,631
US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale Securities	0	0
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale Securities	92,945	87,050
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale Securities	0	0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale Securities	92,945	87,050
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale Securities	0	0
Collateralized Mortgage Backed Securities [Member]
Available-for-sale Securities	95,678	95,795
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale Securities	0	0
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale Securities	95,678	95,795
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale Securities	0	$ 0
Corporate Debt Securities [Member]
Available-for-sale Securities	5,220
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale Securities	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale Securities	5,220
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale Securities	$ 0