v3.25.2
Document And Entity Information - shares
 6 Months Ended
Jun. 30, 2025
Aug. 12, 2025
Document And Entity Information    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2025  
Document Transition Report false  
Entity File Number 000-21344  
Entity Registrant Name FIRST KEYSTONE CORPORATION  
Entity Incorporation, State or Country Code PA  
Entity Tax Identification Number 23-2249083  
Entity Address, Address Line One 111 West Front Street  
Entity Address, City or Town Berwick  
Entity Address, State or Province PA  
Entity Address, Postal Zip Code 18603  
City Area Code 570  
Local Phone Number 752-3671  
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  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   6,218,781
Entity Central Index Key 0000737875  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Amendment Flag false