Note 6 - Fair Value Measurements and Fair Value of Financial Instruments - Assets Measured on Recurring Basis Using Significant Unobservable Inputs (Details) - US States and Political Subdivisions Debt Securities [Member] - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2023	Dec. 31, 2022
Beginning	$ 7,349	$ 8,565
Principal paydowns	(221)	(287)
Change in unrealized gain	(111)	(929)
Beginning	$ 7,017	$ 7,349

Note 6 - Fair Value Measurements and Fair Value of Financial Instruments - Assets Measured on Recurring Basis Using Significant Unobservable Inputs (Details) - US States and Political Subdivisions Debt Securities [Member] - USD ($)
$ in Thousands

9 Months Ended

12 Months Ended

Sep. 30, 2023

Dec. 31, 2022

Beginning

$ 7,349

$ 8,565

Principal paydowns

(221)

(287)

Change in unrealized gain

(111)

(929)

Beginning

$ 7,017

$ 7,349