DEBT - Schedule of Interest Costs Recognized Related to 2026 Notes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Total interest expense recognized	$ 9,779	$ 9,259	$ 9,063
Convertible Debt | 2026 Notes
Debt Instrument [Line Items]
Contractual interest expense	1,164	1,174	1,615
Amortization of debt discount and issuance costs	8,615	8,085	7,546
Total interest expense recognized	$ 9,779	$ 9,259	$ 9,161