Note 5 - Fair Value Measurements - Assets and Liabilities at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Securities available for sale	$ 651,047	$ 656,852
Securities available for sale	651,047	656,852
Fair Value, Inputs, Level 1 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
Fair Value, Inputs, Level 2 [Member]
Securities available for sale	651,047	656,852
Securities available for sale	651,047	656,852
Fair Value, Inputs, Level 3 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
US Treasury Securities [Member]
Securities available for sale	947	936
Securities available for sale	947	936
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	947	936
Securities available for sale	947	936
US Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
US Government Agencies Debt Securities [Member]
Securities available for sale	333,944	336,575
Securities available for sale	333,944	336,575
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	333,944	336,575
Securities available for sale	333,944	336,575
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
US States and Political Subdivisions Debt Securities [Member]
Securities available for sale	149,962	152,200
Securities available for sale	149,962	152,200
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	149,962	152,200
Securities available for sale	149,962	152,200
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
Collateralized Mortgage-Backed Securities [Member]
Securities available for sale	160,453	161,477
Securities available for sale	160,453	161,477
Collateralized Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
Collateralized Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	160,453	161,477
Securities available for sale	160,453	161,477
Collateralized Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
Corporate Debt Securities [Member]
Securities available for sale	5,741	5,664
Securities available for sale	5,741	5,664
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale	0	0
Securities available for sale	0	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	5,741	5,664
Securities available for sale	5,741	5,664
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale	0	0
Securities available for sale	$ 0	$ 0