Debt - Schedule of Debt Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Sep. 30, 2022	Mar. 31, 2022
Debt Instrument [Line Items]
Total long-term debt, gross amount	$ 367,762	$ 316,250	$ 316,250
Total long-term debt, debt discount and issuance costs	(8,475)	(3,347)	(4,082)
Total long-term debt, carrying amount	359,287	312,903	312,168
Senior Notes | 2029 Convertible Notes
Debt Instrument [Line Items]
Total long-term debt, gross amount	230,000	0	0
Total long-term debt, debt discount and issuance costs	(7,209)	0	0
Total long-term debt, carrying amount	222,791	0	0
Senior Notes | 2025 Convertible Notes
Debt Instrument [Line Items]
Total long-term debt, gross amount	103,373	172,500	172,500
Total long-term debt, debt discount and issuance costs	(1,061)	(2,172)	(2,580)
Total long-term debt, carrying amount	102,312	170,328	169,920
Senior Notes | 2024 Convertible Notes
Debt Instrument [Line Items]
Total long-term debt, gross amount	34,389	143,750	143,750
Total long-term debt, debt discount and issuance costs	(205)	(1,175)	(1,502)
Total long-term debt, carrying amount	$ 34,184	$ 142,575	$ 142,248