Organization and Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended
	Feb. 07, 2025	Nov. 25, 2024	Feb. 10, 2025	Dec. 31, 2024	Dec. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Organization And Significant Accounting Policies [Line Items]
Cash, cash equivalents and restricted cash				$ 53,889	$ 58,215	$ 102,685	$ 110,891
Restricted cash				2,100
Available-for-sale securities, at fair value				499,046		$ 578,276
Increase (decrease) in cash and investments				(128,000)
Proceeds from the issuance of pre-funded warrants		$ 25,000		25,000	$ 0
Development regulatory and sales milestones payments				$ 14,100,000
Sarepta | Sarepta Collaboration Agreement
Organization And Significant Accounting Policies [Line Items]
Equity investment		325,000
Cash receivable under collaboration agreement		500,000
Additional cash receivable under collaboration agreement		$ 250,000
Annual installments period		5 years
Enrollment related milestone payments		$ 300,000
Sarepta | Sarepta Collaboration Agreement | Subsequent Event
Organization And Significant Accounting Policies [Line Items]
Equity investment	$ 325,000
Cash receivable under collaboration agreement	500,000
Additional cash receivable under collaboration agreement	$ 250,000
Annual installments period	5 years
Enrollment related milestone payments	$ 300,000
Future potential milestone payments	$ 10,000,000
GSK | GSK-HBV Agreement | Subsequent Event
Organization And Significant Accounting Policies [Line Items]
Development milestone payments			$ 2,500