Document and Entity Information (USD $)
In Millions, except Share data, unless otherwise specified
12 Months Ended
Sep. 30, 2013
Dec. 16, 2013
Mar. 31, 2013
Document Document And Entity Information [Line Items]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Sep. 30, 2013    
Document Fiscal Year Focus 2013    
Document Fiscal Period Focus FY    
Trading Symbol ARWR    
Entity Registrant Name ARROWHEAD RESEARCH CORP    
Entity Central Index Key 0000879407    
Current Fiscal Year End Date --09-30    
Entity Well-known Seasoned Issuer No    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Smaller Reporting Company    
Entity Common Stock, Shares Outstanding   38,700,363  
Entity Public Float     $ 38