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Collaboration and License Agreements - Janssen Pharmaceuticals, Inc. (Details) - USD ($)	Oct. 03, 2018	Jun. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	May 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development, regulatory and sales milestones payments		$ 3,400,000,000
Deferred revenue		16,905,000	$ 74,099,000
Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price	$ 252,700,000
JJDC \| Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	175,000,000
JJDC \| Common Stock Purchase Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from the issuance of common stock	75,000,000
Janssen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment	73,000,000
Janssen \| License Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development, regulatory and sales milestones payments	800,000,000
Janssen \| JNJ-75220795 (ARO-JNJ1)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment				$ 10,000,000	$ 10,000,000
Janssen \| JNJ-3989 (ARO-HBV) Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment	$ 25,000,000
Contract assets		0
Deferred revenue		$ 0