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Fair Value Measurements - Change in Fair Value of Contingent Consideration Obligations (Detail) (USD $) | 12 Months Ended |
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Sep. 30, 2014 | Dec. 31, 2014
Business Combinations [Abstract] |  |
Contingent consideration obligations, Beginning balance | $ 1,595,273 us-gaap_BusinessCombinationContingentConsiderationLiability | $ 3,970,931 us-gaap_BusinessCombinationContingentConsiderationLiability
Change in fair value of contingent consideration | 2,375,658 arwr_BusinessCombinationFairValueOfChangeInContingentConsideration |
Contingent consideration obligations, Ending balance | $ 3,970,931 us-gaap_BusinessCombinationContingentConsiderationLiability | $ 3,970,931 us-gaap_BusinessCombinationContingentConsiderationLiability

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- Definition Business combination fair value of change in contingent consideration. + References No definition available. + Details
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- Definition Amount of liability recognized arising from contingent consideration in a business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 35 -Paragraph 1 -Subparagraph b -URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478 + Details
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- Details
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