Debt - Interest Expense (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 31, 2022	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Debt Instrument [Line Items]
Net loss on extinguishment of debt	$ 3,500			$ 3,545	$ 0
Senior Notes | 2029 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense		$ 2,156	$ 0	2,587	0
Amortization of deferred financing costs		197	0	249	0
Total interest expense		2,353	0	2,836	0
Senior Notes | 2025 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense		614	1,024	1,556	2,048
Amortization of deferred financing costs		120	182	308	389
Net loss on extinguishment of debt		0	0	(5,389)	0
Total interest expense		734	1,206	(3,525)	2,437
Senior Notes | 2024 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense		247	1,033	1,123	2,066
Amortization of deferred financing costs		41	142	179	309
Net loss on extinguishment of debt		0	0	8,935	0
Total interest expense		$ 288	$ 1,175	$ 10,237	$ 2,375