v3.8.0.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2018
May 04, 2018
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q1  
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   4,255,566