| Document and Entity Information | Aug. 04, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 4, 2021 |
| Entity Registrant Name | PREMIER FINANCIAL BANCORP INC |
| Entity Incorporation, State or Country Code | KY |
| Entity File Number | 000-20908 |
| Entity Tax Identification Number | 61-1206757 |
| Entity Address, Address Line One | 2883 FIFTH AVENUE |
| Entity Address, City or Town | HUNTINGTON |
| Entity Address, State or Province | WV |
| Entity Address, Postal Zip Code | 25702 |
| City Area Code | 304 |
| Local Phone Number | 525-1600 |
| 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 | 0000887919 |
| Title of 12(b) Security | Common Stock, no par value |
| Trading Symbol | PFBI |
| Security Exchange Name | NASDAQ |
