Debt - Schedule of Debt Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Debt Instrument [Line Items]
Gross Amount	$ 333,373	$ 316,250	$ 316,250
Debt Issuance Costs	(7,526)	(3,347)
Carrying Amount	325,847	312,903
Long-Term Debt, Gross	367,762	316,250
Debt Issuance Costs	(7,650)	(3,347)
Net carrying amount	360,112	312,903	$ 311,471
Less current portion, Gross Amount	34,389	0
Less current portion, Debt Issuance Costs	(124)	0
Less current portion, carrying amount	34,265	0
Senior Notes
Debt Instrument [Line Items]
Long-Term Debt, Gross	367,762
Senior Notes | 2029 Convertible Notes
Debt Instrument [Line Items]
Gross Amount	230,000	0
Debt Issuance Costs	(6,716)	0
Carrying Amount	223,284	0
Long-Term Debt, Gross	230,000
Senior Notes | 2025 Convertible Notes
Debt Instrument [Line Items]
Gross Amount	103,373	172,500
Debt Issuance Costs	(810)	(2,172)
Carrying Amount	102,563	170,328
Long-Term Debt, Gross	103,373
Debt Issuance Costs	(800)
Senior Notes | 2024 Convertible Notes
Debt Instrument [Line Items]
Gross Amount	34,389	143,750
Debt Issuance Costs	(124)	(1,175)
Carrying Amount	34,265	$ 142,575
Long-Term Debt, Gross	34,389
Debt Issuance Costs	$ (100)