Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

Document and Entity Information - shares
9 Months Ended
Sep. 30, 2020
Oct. 29, 2020
Document And Entity Information [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Amendment Flag false  
Document Period End Date Sep. 30, 2020  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2020  
Document Fiscal Period Focus Q3  
Document Transition Report false  
Entity File Number 001-34079  
Entity Central Index Key 0001228627  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 11-3516358  
Entity Address, Address Line One 15245 Shady Grove Road  
Entity Address, Address Line Two Suite 455  
Entity Address, City or Town Rockville  
Entity Address, State or Province MD  
Entity Address, Postal Zip Code 20850  
City Area Code 240  
Local Phone Number 268-5300  
Title of 12(b) Security Common Stock, $.0001 par value  
Trading Symbol REXN  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Shell Company false  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   4,483,198