| Cover | Nov. 04, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 4, 2021 |
| Entity File Number | 033-21202 |
| Entity Registrant Name | Partners Bancorp |
| Entity Central Index Key | 0000832090 |
| Entity Tax Identification Number | 52-1559535 |
| Entity Incorporation, State or Country Code | MD |
| Entity Address, Address Line One | 2245 Northwood Drive |
| Entity Address, City or Town | Salisbury |
| Entity Address, State or Province | MD |
| Entity Address, Postal Zip Code | 21801 |
| City Area Code | 410 |
| Local Phone Number | 548-1100 |
| Written Communications | false |
| Soliciting Material | true |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | PTRS |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
