| Document and Entity Information Document | Oct. 22, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 22, 2020 |
| Entity Registrant Name | Summit Financial Group, Inc. |
| Entity Central Index Key | 0000811808 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | WV |
| Entity File Number | 0-16587 |
| Entity Tax Identification Number | 55-0672148 |
| Entity Address, Address Line One | 300 North Main Street |
| Entity Address, City or Town | Moorefield |
| Entity Address, State or Province | WV |
| Entity Address, Postal Zip Code | 26836 |
| City Area Code | 304 |
| Local Phone Number | 530-1000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common |
| Trading Symbol | SMMF |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
