Collaboration and License Agreements - Sarepta Therapeutics, Inc. (Details) $ in Thousands				3 Months Ended		6 Months Ended
	Feb. 14, 2025 USD ($)	Feb. 07, 2025 USD ($)	Nov. 25, 2024 USD ($) program obligation	Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue				$ 542,709	$ 0	$ 545,209	$ 3,551
Accounts receivable				2,365		2,365		$ 0
Contract liabilities included in deferred revenue				43,268		43,268		$ 0
Sarepta
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue						542,700
Accounts receivable				2,400		2,400
Contract liabilities included in deferred revenue				$ 43,300		43,300
Sarepta | Sarepta Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of performance obligations | obligation			17
Upfront payment	$ 500,000					500,000
Proceeds from sale of stock		$ 325,000
Equity premium		$ 83,600				83,612
Annual fees			$ 250,000			250,000
Annual installment			$ 50,000
Annual installments period			5 years
Fixed consideration						833,612
Total transaction price						$ 904,855
Enrollment related milestone payments			$ 300,000
Number of collaboration programs | program			13
Collaboration agreement termination notice period prior to any regulatory approval of a licensed product			30 days
Sarepta | Sarepta Collaboration Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of new target programs | program			6
Regulatory milestone payments			$ 180,000
Sales-related milestone payments			700,000
Sarepta | Sarepta Collaboration Agreement | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory milestone payments			110,000
Sales-related milestone payments			$ 500,000