v3.3.1.900
Document and Entity Information - shares
6 Months Ended
Mar. 31, 2016
May. 09, 2016
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2016  
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q2  
Trading Symbol ARWR  
Entity Registrant Name ARROWHEAD PHARMACEUTICALS, INC.  
Entity Central Index Key 0000879407  
Current Fiscal Year End Date --09-30  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   59,960,711