Note 2 - Summary of Significant Accounting Policies - Debt Securities by Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Within one year, amortized cost	$ 11,067
Within one year, fair value	11,012
After one year through two years, amortized cost	5,607
After one year through two years, fair value	5,535
After two years through three years, amortized cost	1,447
After two years through three years, fair value	1,426
Amortized cost	18,121	$ 9,341
Fair value	$ 17,973	$ 9,173