Liability Related to the Sale of Future Royalties - Activity (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024
Liability, Sale Of Future Royalties [Roll Forward]
Beginning carrying value	$ 341,361	$ 268,326	$ 268,326
Milestone payment received	0		50,000
Non-cash interest expense recognized	10,915	$ 12,612	23,035
Ending carrying value	$ 352,276		$ 341,361