Note 12 - Fair Value Measurements - Schedule of Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Available-for-sale debt securities	$ 251,478	$ 200,616
Fair Value, Recurring [Member]
Cash equivalents	120,491	157,990
Investment in equity securities	2,100
Total assets	374,069	358,615
Net investment hedge	10,500	1,915
Foreign exchange contracts	340	213
Total liabilities	10,840	2,128
Foreign exchange contracts		9
Net investment hedge, liability	10,500	1,915
Foreign exchange contracts	340	213
Fair Value, Recurring [Member] | Excluding Convertible Debt Securities [Member]
Available-for-sale debt securities	251,478	198,616
Fair Value, Recurring [Member] | Convertible Debt Securities [Member]
Available-for-sale debt securities		2,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Cash equivalents	119,989	157,990
Investment in equity securities	0
Total assets	143,732	195,574
Net investment hedge	0	0
Foreign exchange contracts	0	0
Total liabilities	0	0
Foreign exchange contracts		0
Net investment hedge, liability	0	0
Foreign exchange contracts	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Excluding Convertible Debt Securities [Member]
Available-for-sale debt securities	23,743	37,584
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Convertible Debt Securities [Member]
Available-for-sale debt securities		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Cash equivalents	502	0
Investment in equity securities	0
Total assets	228,237	161,041
Net investment hedge	10,500	1,915
Foreign exchange contracts	340	213
Total liabilities	10,840	2,128
Foreign exchange contracts		9
Net investment hedge, liability	10,500	1,915
Foreign exchange contracts	340	213
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Excluding Convertible Debt Securities [Member]
Available-for-sale debt securities	227,735	161,032
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Convertible Debt Securities [Member]
Available-for-sale debt securities		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Cash equivalents	0	0
Investment in equity securities	2,100
Total assets	2,100	2,000
Net investment hedge	0	0
Foreign exchange contracts	0	0
Total liabilities	0	0
Foreign exchange contracts		0
Net investment hedge, liability	0	0
Foreign exchange contracts	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Excluding Convertible Debt Securities [Member]
Available-for-sale debt securities	$ 0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Convertible Debt Securities [Member]
Available-for-sale debt securities		$ 2,000