v3.25.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2025
Apr. 30, 2025
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2025  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q1  
Document Transition Report false  
Entity File Number 000-10592  
Entity Registrant Name TRUSTCO BANK CORP NY  
Entity Central Index Key 0000357301  
Entity Incorporation, State or Country Code NY  
Entity Tax Identification Number 14-1630287  
Entity Address, Address Line One 5 SARNOWSKI DRIVE  
Entity Address, City or Town GLENVILLE  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 12302  
City Area Code 518  
Local Phone Number 377-3311  
Title of 12(b) Security Common Stock, $1.00 par value  
Trading Symbol TRST  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   19,019,749