XML 79 R51.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Fair Value Measurements - Assumptions Used in Valuing Derivative Liabilities (Detail) | 12 Months Ended
--- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2013
2010 Warrants |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] |  |  |
Risk-free interest rate | 0.10% | 0.13% | 0.33%
Expected life | 2 months 12 days | 1 year 2 months 12 days | 2 years 2 months 12 days
Dividend yield | 0.00% | 0.00% | 0.00%
Volatility | 75.00% | 69.00% | 69.00%
2012 Warrants |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] |  |  |
Risk-free interest rate | 0.60% | 1.07% | 1.39%
Expected life | 2 years 2 months 12 days | 3 years 2 months 12 days | 4 years 2 months 12 days
Dividend yield | 0.00% | 0.00% | 0.00%
Volatility | 75.00% | 69.00% | 69.00%
2013 Warrants |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] |  |  |
Risk-free interest rate | 0.60% | 1.07% | 1.39%
Expected life | 2 years 3 months 18 days | 3 years 3 months 18 days | 4 years 3 months 18 days
Dividend yield | 0.00% | 0.00% | 0.00%
Volatility | 75.00% | 69.00% | 69.00%
Exchange rights |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items] |  |  |
Risk-free interest rate | 1.00% | 1.07% | 1.39%
Expected life | 2 years 6 months | 3 years 3 months 18 days | 4 years 3 months 18 days
Dividend yield | 0.00% | 0.00% | 0.00%
Volatility | 75.00% | 100.00% | 100.00%

X
- Definition 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. + References No definition available. + Details
Name: | us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssumptionsExpectedDividendRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssumptionsExpectedTerm
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssumptionsExpectedVolatilityRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Risk-free interest rate assumption used in valuing an instrument. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssumptionsRiskFreeInterestRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_ClassOfWarrantOrRightAxis=arwr_TwoThousandTenWarrantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ClassOfWarrantOrRightAxis=arwr_TwoThousandTwelveWarrantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ClassOfWarrantOrRightAxis=arwr_TwoThousandThirteenWarrantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ClassOfWarrantOrRightAxis=arwr_ExchangeRightsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |