Applicable out license term.

No definition available.

Name:	arwr_ApplicableOutLicenseTerm
Namespace Prefix:	arwr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Business acquisition equity interests issued number of shares issued.

+ References

No definition available.

+ Details

Name:	arwr_BusinessAcquisitionEquityInterestsIssuedNumberOfSharesIssued
Namespace Prefix:	arwr_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Business combination consideration promissory note issued.

+ References

No definition available.

+ Details

Name:	arwr_BusinessCombinationConsiderationPromissoryNoteIssued
Namespace Prefix:	arwr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Obligation to pay royalties.

+ References

No definition available.

+ Details

Name:	arwr_ObligationToPayRoyalties
Namespace Prefix:	arwr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of royalty liability.

+ References

No definition available.

+ Details

Name:	arwr_PercentageOfRoyaltyLiability
Namespace Prefix:	arwr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Present value of contingent acquisition consideration.

+ References

No definition available.

+ Details

Name:	arwr_PresentValueOfContingentAcquisitionConsideration
Namespace Prefix:	arwr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase (decrease) in the value of a contingent consideration liability, including, but not limited to, differences arising upon settlement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 50

-Paragraph 4

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=7488404&loc=d3e7008-128479

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=7488404&loc=d3e6927-128479

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

For contingent consideration arrangements and indemnification assets recognized in connection with a business combination, this element represents an estimate of the low-end of the potential range (undiscounted) of the consideration which may be paid.

+ References

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Acquisitions - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended	12 Months Ended
Acquisitions - Additional Information (Detail) (USD $)	Oct. 21, 2011	Jun. 30, 2014	Sep. 30, 2013
Business Acquisition [Line Items]
Obligation to pay royalties		later of (i) the expiration of the last to expire patent right related to such product candidate that was transferred in the Transaction and (ii) ten years after the first commercial sale of such product candidate.
Net present value of contingent consideration	$ 84,935
Contingent consideration - fair value adjustments			1,400,000
Roche Madison Inc
Business Acquisition [Line Items]
Issue of promissory note to Roche	50,000
Issue of Common Stock	1,288,158
Applicable out-license term		90 days
Percentage of royalty liability		3.00%
Cash payments to Roche, minimum		2,500,000
Cash payments to Roche, maximum		$ 6,000,000