Debt - Schedule of Debt Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 30, 2023	Mar. 31, 2023
Debt Instrument [Line Items]
Gross Amount	$ 333,373	$ 333,373	$ 367,762
Debt Issuance Costs	(6,800)	(7,526)	(8,475)
Carrying Amount	326,573	325,847	359,287
Gross Amount	367,762	367,762	367,762
Debt Issuance Costs	(6,842)	(7,650)	(8,475)
Carrying Amount	360,920	360,112	359,287
Less current portion, Gross Amount	34,389	34,389	0
Less current portion, Debt Issuance Costs	(42)	(124)	0
Less current portion, Carrying Amount	34,347	34,265	0
Senior Notes
Debt Instrument [Line Items]
Gross Amount	367,762
2029 Convertible Notes | Senior Notes
Debt Instrument [Line Items]
Gross Amount	230,000	230,000	230,000
Debt Issuance Costs	(6,244)	(6,716)	(7,209)
Carrying Amount	223,756	223,284	222,791
Gross Amount	230,000
2025 Convertible Notes | Senior Notes
Debt Instrument [Line Items]
Gross Amount	103,373	103,373	103,373
Debt Issuance Costs	(556)	(810)	(1,061)
Carrying Amount	102,817	102,563	102,312
Gross Amount	103,373
2024 Convertible Notes | Senior Notes
Debt Instrument [Line Items]
Gross Amount	34,389	34,389	34,389
Debt Issuance Costs	(42)	(124)	(205)
Carrying Amount	34,347	$ 34,265	$ 34,184
Gross Amount	$ 34,389