| Document and Entity Information | Feb. 03, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 3, 2022 |
| Entity Registrant Name | PATHFINDER BANCORP, INC. |
| Entity Central Index Key | 0001609065 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-36695 |
| Entity Incorporation State Country Code | MD |
| Entity Tax Identification Number | 38-3941859 |
| Entity Address, Address Line One | 214 West First Street |
| Entity Address City Or Town | Oswego |
| Entity Address State Or Province | NY |
| Entity Address Postal Zip Code | 13126 |
| City Area Code | 315 |
| Local Phone Number | 343-0057 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security12b Title | Common Stock, $0.01 par value |
| Trading Symbol | PBHC |
| Security Exchange Name | NASDAQ |
