v3.25.2
Cover Page - USD ($)
 12 Months Ended
Jun. 30, 2025
Sep. 04, 2025
Dec. 31, 2024
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Jun. 30, 2025    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Trading Symbol IROQ    
Entity Registrant Name IF BANCORP, INC.    
Entity Central Index Key 0001514743    
Current Fiscal Year End Date --06-30    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Non-accelerated Filer    
Entity Common Stock, Shares Outstanding   3,351,526  
Entity Public Float     $ 56,138,000
Entity Interactive Data Current Yes    
Entity Shell Company false    
Entity Small Business true    
Entity Emerging Growth Company false    
Title of 12(b) Security Common Stock, par value $0.01 per share    
Security Exchange Name NASDAQ    
Entity Address, State or Province IL    
Entity Address, Address Line One 201 East Cherry Street    
Entity Address, City or Town Watseka    
City Area Code 815    
Local Phone Number 432-2476    
Entity Tax Identification Number 45-1834449    
Entity Incorporation, State or Country Code MD    
Entity File Number 001-35226    
Entity Address, Postal Zip Code 60970    
Auditor Name Forvis Mazars, LLP    
Auditor Firm ID 686    
Auditor Location Decatur, Illinois    
Document Financial Statement Error Correction [Flag] false    
ICFR Auditor Attestation Flag false