| Cover | Oct. 26, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 26, 2021 |
| Entity File Number | 1-34682 |
| Entity Registrant Name | EAGLE BANCORP MONTANA, INC. |
| Entity Central Index Key | 0001478454 |
| Entity Tax Identification Number | 27-1449820 |
| Entity Incorporation, State or Country Code | DE |
| 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 | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock par value $0.01 per share |
| Trading Symbol | EBMT |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
