Note 1 - Organization and Summary of Significant Accounting Policies - Fair Value Hierarchy for Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Corporate and municipal debt securities	$ 4,973
Total assets	22,469	$ 26,866
Corporate Debt Securities [Member]
Corporate and municipal debt securities	4,973
Fair Value, Inputs, Level 1 [Member]
Total assets	22,469	26,866
Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Corporate and municipal debt securities	4,973
Money Market Funds [Member]
Money market accounts	17,496	26,866
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Money market accounts	$ 17,496	$ 26,866