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Document And Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2021
Feb. 28, 2022
Jun. 30, 2021
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2021    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 0-11204    
Entity Registrant Name AMERISERV FINANCIAL INC /PA/    
Entity Incorporation, State or Country Code PA    
Entity Tax Identification Number 25-1424278    
Entity Address, Address Line One MAIN & FRANKLIN STREETS    
Entity Address, Address Line Two P.O. BOX 430    
Entity Address, City or Town JOHNSTOWN    
Entity Address, State or Province PA    
Entity Address, Postal Zip Code 15907-0430    
City Area Code 814    
Local Phone Number 533-5300    
Title of 12(b) Security Common Stock    
Trading Symbol ASRV    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag false    
Entity Shell Company false    
Entity Public Float     $ 60,759,199
Entity Common Stock, Shares Outstanding   17,104,309  
Auditor Name S.R. Snodgrass, P.C.    
Auditor Firm ID 74    
Auditor Location Cranberry Township, Pennsylvania    
Entity Central Index Key 0000707605    
Document Fiscal Year Focus 2021    
Document Fiscal Period Focus FY    
Amendment Flag false