Note 6 - Fair Value Measurements and Fair Value of Financial Instruments - Quantitative Information About Significant Unobservable Inputs (Details) $ in Thousands	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Securities available-for-sale	$ 675,941	$ 534,507
Fair Value, Recurring [Member]
Securities available-for-sale	675,941	534,507
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Securities available-for-sale	8,422	8,565
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale	148,031	145,625
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member]
Securities available-for-sale	148,031	145,625
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Securities available-for-sale	$ 8,422	$ 8,565
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Discount Rate [Member]
Securities available-for-sale, rate	0.029	0.029