v3.8.0.1
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2017
Nov. 03, 2017
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2017  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q3  
Trading Symbol RXII  
Entity Registrant Name RXi Pharmaceuticals Corp  
Entity Central Index Key 0001533040  
Current Fiscal Year End Date --12-31  
Entity Filer Category Smaller Reporting Company  
Entity Common Stock, Shares Outstanding   23,697,338