| Document and Entity Information | Mar. 02, 2023 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Mar. 02, 2023 |
| Entity Registrant Name | Great Elm Capital Corp. |
| Entity Incorporation, State or Country Code | MD |
| Entity File Number | 814-01211 |
| Entity Tax Identification Number | 81-2621577 |
| 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 |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001675033 |
| Common Stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common stock, $0.01 par value |
| Trading Symbol | GECC |
| Security Exchange Name | NASDAQ |
| 6.75% Notes due 2025 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | 6.75% Notes due 2025 |
| Trading Symbol | GECCM |
| Security Exchange Name | NASDAQ |
| 6.50% Notes due 2024 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | 6.50% Notes due 2024 |
| Trading Symbol | GECCN |
| Security Exchange Name | NASDAQ |
| 5.875% Notes due 2026 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | 5.875% Notes due 2026 |
| Trading Symbol | GECCO |
| Security Exchange Name | NASDAQ |
