Document and Entity Information
6 Months Ended
Mar. 31, 2015
May 08, 2015
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2015  
Document Fiscal Year Focus 2015  
Document Fiscal Period Focus Q2  
Trading Symbol ARWR  
Entity Registrant Name ARROWHEAD RESEARCH CORP  
Entity Central Index Key 0000879407  
Current Fiscal Year End Date --09-30  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   59,498,362