DEBT - Interest Costs Recognized on 2026 Notes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Debt Instrument [Line Items]
Total interest expense recognized	$ 2,303	$ 2,163	$ 4,566	$ 4,300
Convertible Debt | 2026 Notes
Debt Instrument [Line Items]
Contractual interest expense	298	307	591	600
Amortization of debt discount and issuance costs	2,006	1,857	3,975	3,701
Total interest expense recognized	$ 2,304	$ 2,164	$ 4,566	$ 4,301