| Cover | Dec. 10, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 10, 2020 |
| Entity File Number | 2-88927 |
| Entity Registrant Name | First Keystone Corporation |
| Entity Central Index Key | 0000737875 |
| Entity Tax Identification Number | 23-2249083 |
| Entity Incorporation, State or Country Code | PA |
| Entity Address, Address Line One | 111 West Front Street |
| Entity Address, City or Town | Berwick |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 18603 |
| City Area Code | 570 |
| Local Phone Number | 752-3671 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
