Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Nov. 01, 2019
Document and Entity Information    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Entity Registrant Name ENZON PHARMACEUTICALS, INC.  
Entity Central Index Key 0000727510  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Trading Symbol ENZN  
Entity Common Stock, Shares Outstanding   44,214,603
Entity Shell Company false  
Entity Emerging Growth Company false  
Entity Small Business true