Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Debt Instrument [Line Items]
Amortization of deferred financing costs			$ 725	$ 807
Senior Notes | 2032 Senior Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 184	$ 0	184	0
Amortization of deferred financing costs	7	0	7	0
Total interest expense	191	0	191	0
Senior Notes | 2029 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	2,157	2,157	4,313	4,313
Amortization of deferred financing costs	217	228	466	472
Total interest expense	2,374	2,385	4,779	4,785
Senior Notes | 2025 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	614	614	1,228	1,228
Amortization of deferred financing costs	119	123	252	254
Total interest expense	733	737	1,480	1,482
Senior Notes | 2024 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	0	247	0	494
Amortization of deferred financing costs	0	39	0	81
Total interest expense	$ 0	$ 286	$ 0	$ 575