DEBT - Interest Costs Recognized on 2026 Notes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Debt Instrument [Line Items]
Total interest expense recognized	$ 2,407	$ 2,303	$ 4,805	$ 4,566
Convertible Debt | 2026 Notes
Debt Instrument [Line Items]
Contractual interest expense	288	298	581	591
Amortization of debt discount and issuance costs	2,119	2,005	4,224	3,975
Total interest expense recognized	$ 2,407	$ 2,303	$ 4,805	$ 4,566