Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Net loss on extinguishment of debt	$ 0	$ 3,545
Senior Notes | 2029 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	2,156	431
Amortization of deferred financing costs	244	52
Total interest expense	2,400	483
Senior Notes | 2025 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	614	942
Amortization of deferred financing costs	131	188
Net loss on extinguishment of debt	0	(5,389)
Total interest expense	745	(4,259)
Senior Notes | 2024 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	247	876
Amortization of deferred financing costs	42	138
Net loss on extinguishment of debt	0	8,935
Total interest expense	$ 289	$ 9,949