Debt - Interest Expense (Details) - Senior Notes - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
2029 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 2,156	$ 2,156
Amortization of deferred financing costs	249	244
Total interest expense	2,405	2,400
2025 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	614	614
Amortization of deferred financing costs	133	131
Total interest expense	747	745
2024 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	0	247
Amortization of deferred financing costs	0	42
Total interest expense	$ 0	$ 289