Note 5 - Other Comprehensive Income (Loss) - Changes in Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Balance as of September 30, 2021	$ 147,582	$ 103,824	$ 82,754
Other comprehensive income (loss)	1,354	(1,898)	0
Balance at September 30, 2022	315,163	147,582	103,824
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member]
Balance as of September 30, 2021	(1,224)	0
Other comprehensive income (loss)	542	(1,224)
Balance at September 30, 2022	(682)	(1,224)	0
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Balance as of September 30, 2021	(674)	0
Other comprehensive income (loss)	812	(674)
Balance at September 30, 2022	138	(674)	0
AOCI Attributable to Parent [Member]
Balance as of September 30, 2021	(1,898)	0	0
Other comprehensive income (loss)	1,354	(1,898)
Balance at September 30, 2022	$ (544)	$ (1,898)	$ 0