Organization and Significant Accounting Policies (Details) - USD ($)		1 Months Ended	12 Months Ended
	Nov. 09, 2022	Apr. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Organization And Significant Accounting Policies [Line Items]
Cash, cash equivalents and restricted cash			$ 110,891,000	$ 108,005,000	$ 184,434,000	$ 143,583,000
Restricted cash			7,900,000	7,300,000
Available-for-sale securities, at fair value			292,735,000	0
Net increase (decrease) in cash and investments			(78,600,000)
Development regulatory and sales milestones payments			2,800,000,000
Proceeds from sale of marketable debt securities		$ 122,300,000
Intangible assets subject to amortization, impairment			$ 0	$ 0
Minimum
Organization And Significant Accounting Policies [Line Items]
Property and equipment, useful life			3 years
Maximum
Organization And Significant Accounting Policies [Line Items]
Amount insured in FDIC per account			$ 250,000
Property and equipment, useful life			7 years
Royalty Pharma Agreement
Organization And Significant Accounting Policies [Line Items]
Upfront payment	$ 250,000,000
Collaboration and License agreements
Organization And Significant Accounting Policies [Line Items]
Upfront milestone payment received			$ 110,000,000