Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

v3.8.0.1
Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2017
Mar. 07, 2018
Jun. 30, 2017
Document And Entity Information [Abstract]      
Entity Registrant Name FINJAN HOLDINGS, INC.    
Trading Symbol FNJN    
Entity Central Index Key 0001366340    
Current Fiscal Year End Date --12-31    
Entity Filer Category Smaller Reporting Company    
Document Type 10-K    
Document Period End Date Dec. 31, 2017    
Document Fiscal Year Focus 2017    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Common Stock, Shares Outstanding   27,719,828  
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Public Float     $ 70,542,789