DEBT - Narrative (Details)			3 Months Ended	6 Months Ended
	Feb. 13, 2024 USD ($)	Feb. 05, 2021 USD ($) tradingDay shares $ / shares	Mar. 31, 2024 USD ($) shares	Mar. 31, 2024 USD ($) shares	Sep. 30, 2023 USD ($)	Jan. 13, 2023	Feb. 28, 2021 USD ($)	Feb. 02, 2021 $ / shares
Debt Instrument [Line Items]
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]			Convertible senior notes	Convertible senior notes
Revolving Credit Facility | SOFR
Debt Instrument [Line Items]
Unused revolving line facility fee (as a percent)	0.25%
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Debt issuance costs	$ 300,000
Maximum borrowing capacity	35,000,000
Additional value, line of credit facility, maximum borrowing capacity	15,000,000
Indebtedness amount	500,000
Carrying amount			$ 0	$ 0
Line of Credit | Revolving Credit Facility | SOFR
Debt Instrument [Line Items]
Commitment fees	$ 87,500
Foreign Letter Of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Cash deposit, percentage	115.00%
2026 Notes | Significant Other Observable Inputs (Level 2)
Debt Instrument [Line Items]
Fair value			154,700,000	154,700,000
2026 Notes | Convertible Debt
Debt Instrument [Line Items]
Debt issued			$ 155,300,000	$ 155,300,000			$ 155,300,000
Debt interest rate (as a percent)		0.75%	75.00%	75.00%
Debt conversion ratio (per $1,000 principal amount)		0.0479731000
Debt conversion price (in dollars per share) | $ / shares		$ 20.85
Conversion price premium percentage								37.50%
Proceeds from debt offerings, net of discounts, commissions and expenses		$ 149,700,000
Debt issuance costs		$ 5,500,000
Remaining unamortized debt discount			$ 15,758,000	$ 15,758,000	$ 19,734,000
Carrying amount			$ 139,492,000	$ 139,492,000	$ 135,516,000
2026 Notes | Convertible Debt | Common Stock
Debt Instrument [Line Items]
Share price (in dollars per share) | $ / shares								$ 15.16
2026 Notes | Convertible Debt | During any calendar quarter commencing after the calendar quarter ending on June 30, 2021
Debt Instrument [Line Items]
Debt conversion price percentage		130.00%
Trading days in period (in days) | tradingDay		20
Consecutive trading days in period (in days) | tradingDay		30
2026 Notes | Convertible Debt | Measurement period
Debt Instrument [Line Items]
Debt conversion price percentage		98.00%
Consecutive trading days in period (in days) | tradingDay		5
2026 Notes | Convertible Debt | Embedded Derivative Financial Instruments
Debt Instrument [Line Items]
Payment costs related to hedge transactions		$ 9,300,000
Embedded derivative, fair value of embedded derivative liability		33,200,000
Value of remaining embedded derivative allocated to host contract		$ 116,500,000
Derivative interest rate			6.71%	6.71%
Remaining unamortized debt discount			$ 15,800,000	$ 15,800,000
Remaining debt discount amortization period (in years)				1 year 10 months 2 days
2026 Notes | Convertible Debt | Interest Rate Period One
Debt Instrument [Line Items]
Additional interest percentage						0.25%
Interest rate threshold period						90 days
2026 Notes | Convertible Debt | Interest Rate Period Two
Debt Instrument [Line Items]
Additional interest percentage						0.50%
Interest rate threshold period						180 days
Additional Notes | Convertible Debt
Debt Instrument [Line Items]
Option period to purchase additional notes (in days)		13 days
Additional aggregate principal amount purchased		$ 20,250,000
Notes Hedge | Convertible Debt
Debt Instrument [Line Items]
Debt conversion price (in dollars per share) | $ / shares		$ 20.85
Conversion price premium percentage								75.00%
Number of shares that can initially be converted into common stock (in shares) | shares		7,400,000
Strike price of warrants (in dollar per share) | $ / shares		$ 26.53
Senior notes hedge balance		$ 33,200,000
Shares purchased under the notes hedge (in shares) | shares				0
Increase in additional paid-in-capital for sale or warrants		$ 23,900,000
Warrants exercised (in shares) | shares				0
Warrants outstanding (in shares) | shares			0	0
Notes Hedge | Convertible Debt | Observation period
Debt Instrument [Line Items]
Consecutive trading days in period (in days) | tradingDay		80
Incremental dilution of earnings per share of warrants (in shares) | shares			0