Note 4 - Fair Value Measurements - Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
cash equivalents	$ 26,467	$ 15
Investment securities:	136,629	28,549
Fair Value, Inputs, Level 1 [Member]
cash equivalents	26,467	15
Investment securities:	0	0
Fair Value, Inputs, Level 2 [Member]
cash equivalents	0	0
Investment securities:	136,629	28,549
Fair Value, Inputs, Level 3 [Member]
cash equivalents	0	0
Investment securities:	0	0
Money Market Funds [Member]
cash equivalents	26,467	15
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
cash equivalents	26,467	15
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
cash equivalents	0	0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
cash equivalents	0	0
Certificates of Deposit [Member]
Investment securities:	8,115	13,456
Certificates of Deposit [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities:	0	0
Certificates of Deposit [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities:	8,115	13,456
Certificates of Deposit [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities:	0	0
US Treasury Securities [Member]
Investment securities:	128,514	15,093
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities:	0	0
US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities:	128,514	15,093
US Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities:	$ 0	$ 0