Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

Document and Entity Information - shares
6 Months Ended
Jun. 30, 2018
Jul. 25, 2018
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 Jun. 30, 2018  
Trading Symbol FNJN  
Current Fiscal Year End Date --12-31  
Entity Filer Category Smaller Reporting Company  
Entity Common Stock, Shares Outstanding   27,244,160
Document Fiscal Period Focus Q2  
Document Fiscal Year Focus 2018