Note 3 - Cash and Investments - Amortized Cost and Fair Value of Short-Term Investments (Details) $ in Thousands	Jun. 30, 2023 USD ($)
U.S. treasury securities, AC	$ 19,831
U.S. treasury securities, CV	19,831
U.S. treasury securities, unrealized losses	0
U.S. treasury securities, FV	19,831
US Treasury Securities [Member]
U.S. treasury securities, AC	19,831
U.S. treasury securities, CV	19,831
U.S. treasury securities, unrealized losses	0
U.S. treasury securities, FV	$ 19,831