Note 1 - Organization and Significant Accounting Policies - Debt Securities by Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Within one year, amortized cost	$ 12,136
Within one year, fair value	12,056
After one year through two years, amortized cost	3,664
After one year through two years, fair value	3,658
Amortized cost	15,800	$ 9,341
Fair value	$ 15,714	$ 9,173