Collaboration and License Agreements - Glaxosmithkline Intellectual Property (No. 3) Limited - Additional Information (Detail) $ in Thousands			1 Months Ended	3 Months Ended		6 Months Ended
	Nov. 22, 2021 USD ($) Obligation Bundle	Oct. 03, 2018 USD ($)	Jan. 31, 2022 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues				$ 151,805	$ 32,811	$ 179,244	$ 54,113
Contract liabilities				$ 97,869		97,869		$ 111,055
Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price		$ 252,700
Collaboration and License agreements | GSK
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment	$ 120
Milestone payment receivable at start of phase two	30
Milestone payment receivable upon achievement of phase two and first patient dosed in phase three	100
Tiered royalties on net product sales receive description				The Company is further eligible to receive tiered royalties on net product sales in a range of mid-teens to twenty percent.
Collaboration and License agreements | Maximum | GSK
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Commercial milestone payments at first commercial sale	190
Sales-related milestone payments	$ 590
ARO-HSD Agreement | GSK
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of distinct bundle | Bundle	1
Number of distinct performance obligations | Obligation	1
Initial transaction price	$ 120,000
Cash received as due under collaboration agreement			$ 120,000
Performance obligation related to agreement, upfront payment				$ 120,000		120,000
Revenues				120,000	$ 0	120,000	$ 0
Contract assets				0		0
Contract liabilities				$ 0		$ 0