| Document and Entity Information | Oct. 19, 2021 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 19, 2021 |
| Entity File Number | 0-11204 |
| Entity Registrant Name | AMERISERV FINANCIAL, Inc. |
| Entity Incorporation, State or Country Code | PA |
| Entity Tax Identification Number | 25-1424278 |
| Entity Address, Address Line One | Main and Franklin Streets |
| Entity Address, City or Town | Johnstown |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 15901 |
| City Area Code | 814 |
| Local Phone Number | 533-5300 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | ASRV |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000707605 |
| Amendment Flag | false |
