Balance Sheet Accounts - Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued R&D expenses	$ 42,963	$ 28,069
Accrued R&D expenses; co-development	28,755	23,351
Accrued capital expenditures	358	4,206
Other	6,374	7,391
Total accrued expenses	$ 78,450	$ 63,017