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Agreement date.

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Cash received as due under collaboration agreement.

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Milestone payment received.

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Number of agreements.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

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The cash inflow from the additional capital contribution to the entity.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Collaboration and License Agreements - Amgen, Inc - Additional Information (Detail) $ in Thousands		3 Months Ended
	Sep. 28, 2016 USD ($) Agreement	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($)	Jul. 31, 2020 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		$ 27,439	$ 21,303
Contract liabilities		108,652		$ 111,055
Collaboration and License agreements \| Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date	Sep. 28, 2016
Number of agreements \| Agreement	2
Cash received as due under collaboration agreement	$ 35,000
License Collaboration And Stock Purchase Agreement \| Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from the issuance of common stock	21,500
Olpasiran and ARO-AMG1 Agreement \| Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments	$ 30,000				$ 20,000
Revenues		0	$ 0
Contract liabilities		0
Contract assets		0
Olpasiran Agreement \| Amgen \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional remaining development regulatory and sales milestones payments		$ 400,000