Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2019
Feb. 11, 2020
Jun. 30, 2019
Document and Entity Information      
Entity Registrant Name GENOCEA BIOSCIENCES, INC.    
Entity Central Index Key 0001457612    
Current Fiscal Year End Date --12-31    
Entity Filer Category Accelerated Filer    
Document Type 10-K    
Document Period End Date Dec. 31, 2019    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Common Stock, Shares Outstanding   27,643,773  
Entity Small Business true    
Entity Emerging Growth Company false    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Shell Company false    
Entity Public Float     $ 73,983,101