Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Other Commitments [Line Items]
Facility and equipment rent expense	$ 171,500arwr_FacilityAndEquipmentRentExpense	$ 145,000arwr_FacilityAndEquipmentRentExpense
Provision for recorded liabilities	0us-gaap_RetainedEarningsAppropriated
Future commitments	43,100,000us-gaap_PurchaseObligation
Commitments expected to be incurred in fiscal 2015	31,600,000
Commitments expected to be incurred beyond fiscal 2015	11,500,000
Corporate Headquarters In Pasadena
Other Commitments [Line Items]
Rental expense	23,000
Operating lease expiration date	Sep. 30, 2019
Percentage of increase in annual rental cost	3.00%
Research Facility in Madison
Other Commitments [Line Items]
Rental expense	25,000
Operating lease expiration date	Feb. 28, 2019
Other rental expenses including common area maintenance and real estate taxes	16,000
Utilities costs per month	15,000
Increase in total monthly expenditures	75,000
Research Facility in Madison \| Assets Held under Capital Leases
Other Commitments [Line Items]
Monthly payments under capital lease	$ 19,000

Facility and equipment rent expense.

No definition available.

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- Definition

Increase in monthly expenditure due to utilities costs.

+ References

No definition available.

+ Details

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- Definition

Other rental expenses.

+ References

No definition available.

+ Details

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- Definition

Payments under capital lease.

+ References

No definition available.

+ Details

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- Definition

Percentage of increase in annual rental cost.

+ References

No definition available.

+ Details

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- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

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- Definition

Date which lease or group of leases is set to expire, in CCYY-MM-DD format.

+ References

No definition available.

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- Definition

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Minimum amount of purchase arrangement maturing in the next fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

+ References

No definition available.

+ Details

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- Definition

Minimum amount of purchase arrangement maturing in the second fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

+ References

No definition available.

+ Details

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- Definition

A segregation of retained earnings which is unavailable for dividend distribution. Includes also retained earnings appropriated for loss contingencies.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Subparagraph (SX 210.7-03.23(4))

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-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 24

-Subparagraph a(4)

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- Definition

Utilities costs incurred during the reporting period for services, such as water, sewer, gas, electricity and telephone required to operate a building.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.2)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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