| Document and Entity Information | Apr. 27, 2023 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Apr. 27, 2023 |
| Entity File Number | 001-35226 |
| Entity Registrant Name | IF BANCORP, INC. |
| Entity Central Index Key | 0001514743 |
| Entity Incorporation, State or Country Code | MD |
| Entity Tax Identification Number | 45-1834449 |
| Entity Address, Address Line One | 201 East Cherry Street |
| Entity Address, City or Town | Watseka |
| Entity Address, State or Province | IL |
| Entity Address, Postal Zip Code | 60970 |
| City Area Code | 815 |
| Local Phone Number | 432-2476 |
| Title of 12(b) Security | IROQ |
| Trading Symbol | IROQ |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
