Note 16 - Fair Value Measurements - Assets and Liabilities at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Securities available for sale, at fair value	$ 304,282	$ 236,131
Fair Value, Inputs, Level 1 [Member]
Securities available for sale, at fair value	0	0
Fair Value, Inputs, Level 2 [Member]
Securities available for sale, at fair value	304,282	236,131
Fair Value, Inputs, Level 3 [Member]
Securities available for sale, at fair value	0	0
US Government Agencies Debt Securities [Member]
Securities available for sale, at fair value	285,598	212,464
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale, at fair value	0	0
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale, at fair value	285,598	212,464
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale, at fair value	0	0
US States and Political Subdivisions Debt Securities [Member]
Securities available for sale, at fair value	11,693	16,475
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale, at fair value	0	0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale, at fair value	11,693	16,475
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale, at fair value	0	0
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, at fair value	930	1,319
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale, at fair value	0	0
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale, at fair value	930	1,319
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale, at fair value	0	0
Corporate Debt Securities [Member]
Securities available for sale, at fair value	5,898	5,746
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale, at fair value	0	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale, at fair value	5,898	5,746
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale, at fair value	0	0
Other Securities [Member]
Securities available for sale, at fair value	163	127
Other Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale, at fair value	0	0
Other Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale, at fair value	163	127
Other Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale, at fair value	$ 0	$ 0