Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

Document and Entity Information - shares
3 Months Ended
Mar. 31, 2019
May 01, 2019
Document And Entity Information [Abstract]    
Entity Registrant Name FINJAN HOLDINGS, INC.  
Entity Central Index Key 0001366340  
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2019  
Trading Symbol FNJN  
Current Fiscal Year End Date --12-31  
Entity Filer Category Non-accelerated Filer  
Entity Common Stock, Shares Outstanding   27,610,524
Document Fiscal Period Focus Q1  
Document Fiscal Year Focus 2019  
Entity Emerging Growth Company false  
Entity Small Business true