Additional amount of common stock shares agreed to sell upon exercise of option.

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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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Option payments, and development, regulatory and sales milestone payments.

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Trading Period used to calculate share price of common stock surrounding option exercise date.

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Trading period used to calculate weighted average price of common stock listed in stock market.

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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 of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Per share or per unit amount of equity securities issued.

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Collaboration and License Agreements - Amgen, Inc - Additional Information (Detail)		1 Months Ended		3 Months Ended			9 Months Ended
	Sep. 28, 2016 USD ($) Agreement $ / shares shares	Nov. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) $ / shares	Jun. 30, 2017 USD ($)	Aug. 01, 2018 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Stock issued, price per share \| $ / shares				$ 5.25			$ 5.25
Proceeds from the issuance of common stock							$ 56,585,035	$ 12,419,119
Revenue generated from work orders				$ 727,375		$ 9,342,498	$ 4,887,321	$ 22,693,923
Type of Revenue [Extensible List]				arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember		arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember
Collaboration and License agreements \| Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date	Sep. 28, 2016
Number of agreements \| Agreement	2
ARO-AMG1 Agreement \| Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional amount of common stock shares agreed to sell upon exercise of option	$ 5,000,000
Number of trading days, used to calculate share price of Common Stock, surrounding option exercise date	30 days
Cash received as due under collaboration agreement			$ 5,000,000
Deferred revenue			$ 5,000,000	$ 600,000			$ 600,000
Deferred revenue amortized into revenue				600,000		$ 600,000	2,000,000	$ 2,000,000
Collaboration and License agreements \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option payments, and development, regulatory and sales milestone payments.	$ 617,000,000
Collaboration and License agreements \| Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash received as due under collaboration agreement	35,000,000
Proceeds from the issuance of common stock	$ 21,500,000
AMG-890 (ARO-LPA) Agreement \| Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash received as due under collaboration agreement		$ 30,000,000
Deferred revenue		$ 30,000,000		0			0
Deferred revenue amortized into revenue					$ 2,700,000	7,900,000		19,400,000
AMG-890 (ARO-LPA) Agreement \| Amgen \| Subsequent Event
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amgen milestone payment									$ 10,000,000
AMG 890 (ARO-LPA) and ARO-AMG1 Agreement \| Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue generated from work orders				$ 100,000		$ 800,000	$ 300,000	$ 1,400,000
Type of Revenue [Extensible List]				us-gaap:LicenseAndServiceMember		us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Common Stock Purchase Agreement \| Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date	Sep. 28, 2016
Shares issued \| shares	3,002,793
Stock issued, price per share \| $ / shares	$ 7.16
Common Stock Purchase Agreement \| Amgen \| NASDAQ
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of trading days, used to calculate weighted average price of Common Stock, listed in stock market	30 days