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Document And Entity Information - shares
9 Months Ended
Sep. 30, 2018
Oct. 31, 2018
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2018  
Document Fiscal Period Focus Q3  
Document Fiscal Year Focus 2018  
Entity Registrant Name FRANKLIN FINANCIAL SERVICES CORP /PA/  
Entity Central Index Key 0000723646  
Current Fiscal Year End Date --12-31  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   4,399,135
Trading Symbol fraf  
Entity Small Business true  
Entity Emerging Growth Company false