| Document And Entity Information | Jan. 25, 2022 |
| Document Information [Line Items] | |
| Entity, Registrant Name | Eagle Bancorp Montana, Inc. |
| Document, Type | 8-K |
| Document, Period End Date | Jan. 25, 2022 |
| Entity, Incorporation, State or Country Code | DE |
| Entity, File Number | 1-34682 |
| Entity, Tax Identification Number | 27-1449820 |
| Entity, Address, Address Line One | 1400 Prospect Ave. |
| Entity, Address, City or Town | Helena |
| Entity, Address, State or Province | MT |
| Entity, Address, Postal Zip Code | 59601 |
| City Area Code | 406 |
| Local Phone Number | 442-3080 |
| Written Communications | true |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | EBMT |
| Security Exchange Name | NASDAQ |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0001478454 |
