Note 7 - Fair Value Measurements - Fair Value Hierarchy for Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Corporate, municipal debt and treasury securities	$ 5,305	$ 5,230
Total assets	24,661
Corporate Debt Securities [Member]
Corporate, municipal debt and treasury securities	5,305
Money Market Funds [Member]
Money market accounts	19,356
Fair Value, Inputs, Level 1 [Member]
Total assets	24,661
Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Corporate, municipal debt and treasury securities	5,305
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Money market accounts	$ 19,356