Liability Related to the Sale of Future Royalties - Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Liability, Sale Of Future Royalties [Roll Forward]
Beginning carrying value	$ 341,361	$ 268,326
Upfront payment received	0	0
Milestone payment received	0	50,000
Non-cash interest expense recognized	26,036	23,035	$ 18,326
Ending carrying value	$ 367,397	$ 341,361	$ 268,326