Note 3 - Cash and Investments - Amortized Cost and Fair Value of Short-Term Investments (Details) $ in Thousands	Sep. 30, 2023 USD ($)
U.S. treasury securities, AC	$ 22,796
U.S. treasury securities, CV	22,796
U.S. treasury securities, unrealized losses	0
U.S. treasury securities, FV	22,796
US Treasury Securities [Member]
U.S. treasury securities, AC	22,796
U.S. treasury securities, CV	22,796
U.S. treasury securities, unrealized losses	0
U.S. treasury securities, FV	$ 22,796