Property and Equipment - Summary of Property and Equipment (Detail) (USD $)	Dec. 31, 2014	Sep. 30, 2014
Property Plant And Equipment [Abstract]
Computers, office equipment and furniture	$ 374,535us-gaap_FurnitureAndFixturesGross	$ 334,162us-gaap_FurnitureAndFixturesGross
Research equipment	5,010,151arwr_ResearchEquipment	4,614,176arwr_ResearchEquipment
Software	69,623	69,623
Leasehold improvements	3,117,537us-gaap_LeaseholdImprovementsGross	3,045,022us-gaap_LeaseholdImprovementsGross
Total gross fixed assets	8,571,846us-gaap_PropertyPlantAndEquipmentGross	8,062,983us-gaap_PropertyPlantAndEquipmentGross
Less: Accumulated depreciation and amortization	(4,447,405)	(4,190,230)
Property and equipment, net	$ 4,124,441us-gaap_PropertyPlantAndEquipmentNet	$ 3,872,753us-gaap_PropertyPlantAndEquipmentNet

Research equipment.

No definition available.

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- Definition

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.14)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 14

-Article 5

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- Definition

Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 985

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

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- Definition

Amount before accumulated depreciation of equipment commonly used in offices and stores that have no permanent connection to the structure of a building or utilities. Examples include, but are not limited to, desks, chairs, tables, and bookcases.

+ References

+ Details

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- Definition

Amount before accumulated depreciation of additions or improvements to assets held under a lease arrangement.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

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- Definition

Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

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-Topic 210

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-Paragraph 1

-Subparagraph (SX 210.5-02.13)

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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-Name Accounting Standards Codification

-Topic 210

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-Subparagraph (SX 210.5-02.13)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Subparagraph a

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

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