v3.25.2
Document And Entity Information - shares
6 Months Ended
Jun. 30, 2025
Aug. 04, 2025
Document Information [Line Items]    
Entity Central Index Key 0001303942  
Entity Registrant Name BankFinancial CORP  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Document Fiscal Period Focus Q2  
Document Fiscal Year Focus 2025  
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2025  
Document Transition Report false  
Entity File Number 0-51331  
Entity Incorporation, State or Country Code MD  
Entity Tax Identification Number 75-3199276  
Entity Address, Address Line One 60 North Frontage Road  
Entity Address, City or Town Burr Ridge  
Entity Address, State or Province IL  
Entity Address, Postal Zip Code 60527  
City Area Code 800  
Local Phone Number 894-6900  
Title of 12(b) Security Common Stock, par value $0.01 per share  
Trading Symbol BFIN  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   12,460,678