| Document and Entity Information | Sep. 30, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | PREMIER FINANCIAL CORP |
| Amendment Flag | false |
| Entity Central Index Key | 0000946647 |
| Document Type | 8-K |
| Document Period End Date | Sep. 30, 2020 |
| Entity Incorporation State Country Code | OH |
| Entity File Number | 0-26850 |
| Entity Tax Identification Number | 34-1803915 |
| Entity Address, Address Line One | 601 Clinton Street |
| Entity Address, City or Town | Defiance |
| Entity Address, State or Province | OH |
| Entity Address, Postal Zip Code | 43512 |
| City Area Code | (419) |
| Local Phone Number | 782-5015 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, Par Value $0.01 Per Share |
| Trading Symbol | PFC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
