| Document and Entity Information | May 25, 2023 |
| Document and Entity Information | |
| Entity Registrant Name | FIRST KEYSTONE CORPORATION |
| Document Type | 8-K |
| Entity File Number | 000-21344 |
| Entity Tax Identification Number | 23-2249083 |
| Document Period End Date | May 25, 2023 |
| 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 Issuer Tender Offer | false |
| Pre-commencement Tender Offer | false |
| Amendment Flag | false |
| Title of 12(b) Security | Common stock |
| Trading Symbol | FKYS |
| Entity Incorporation, State or Country Code | PA |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000737875 |
