Liability Related to the Sale of Future Royalties (Details) - USD ($) $ in Thousands		12 Months Ended
	Nov. 09, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-cash interest expense on liability related to the sale of future royalties		$ 18,326	$ 0	$ 0
Royalty Pharma Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	$ 250,000
Milestone payment receivable	160,000
Milestone payment receivable upon achievement of enrollment in phase 3 clinical trial	50,000
Milestone payment receivable upon FDA approval	50,000
Milestone payment receivable upon receipt of royalty payments	60,000
Royalty payment threshold	70,000
Non-cash interest expense on liability related to the sale of future royalties		$ 18,300
Royalty Pharma Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price	$ 410,000