INVESTMENTS - Investments by Type of Security (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 30, 2023
Debt Securities, Available-for-sale [Line Items]
Cost	$ 49,439	$ 76,245
Gross Unrealized Gains	2	1
Gross Unrealized Losses	(117)	(242)
Fair Market Value	49,324	76,004
Short-Term | U.S. Treasury
Debt Securities, Available-for-sale [Line Items]
Cost	19,203	40,329
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(51)	(76)
Fair Market Value	19,152	40,254
Short-Term | Commercial Paper
Debt Securities, Available-for-sale [Line Items]
Cost	16,252
Gross Unrealized Gains	1
Gross Unrealized Losses	(10)
Fair Market Value	16,243
Short-Term | Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Cost	7,626	34,545
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(35)	(99)
Fair Market Value	7,592	34,446
Long-Term | U.S. Treasury
Debt Securities, Available-for-sale [Line Items]
Cost	4,397	1,371
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(18)	(67)
Fair Market Value	4,379	$ 1,304
Long-Term | Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Cost	1,961
Gross Unrealized Gains	0
Gross Unrealized Losses	(3)
Fair Market Value	$ 1,958