Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2024	Jun. 30, 2023
Debt Instrument [Line Items]
(Gain) loss on extinguishment			$ 3,500	$ 0	$ 3,545
Senior Notes | 2029 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 2,156	$ 2,157		6,469	4,744
Amortization of deferred financing costs	242	239		714	488
Total interest expense	2,398	2,396		7,183	5,232
Senior Notes | 2025 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	613	614		1,841	2,170
Amortization of deferred financing costs	123	121		377	429
(Gain) loss on extinguishment	0	0		0	(5,389)
Total interest expense	736	735		2,218	(2,790)
Senior Notes | 2024 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	248	247		742	1,370
Amortization of deferred financing costs	40	39		121	218
(Gain) loss on extinguishment	0	0		0	8,935
Total interest expense	$ 288	$ 286		$ 863	$ 10,523