Note 4 - Fair Value Measurements - Fair Value of Financial Instruments (Details) - Money Market Funds [Member] - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Estimate of Fair Value Measurement [Member]
Cash equivalents	$ 63,450	$ 67,801
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash equivalents	63,450	67,801
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash equivalents	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash equivalents	0	0
Reported Value Measurement [Member]
Cash equivalents	$ 63,450	$ 67,801