| Document and Entity Information | May 14, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 14, 2021 |
| Entity Registrant Name | Great Elm Group, Inc. |
| Entity Central Index Key | 0001831096 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-39832 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 85-3622015 |
| Entity Address, Address Line One | 800 South Street |
| Entity Address, Address Line Two | Suite 230 |
| Entity Address, City or Town | Waltham |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02453 |
| City Area Code | 617 |
| Local Phone Number | 375-3006 |
| 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 $0.001 per share |
| Trading Symbol | GEG |
| Security Exchange Name | NASDAQ |
