v3.26.1
Document And Entity Information - shares
 9 Months Ended
Mar. 31, 2026
May 07, 2026
Document Information Line Items    
Entity Central Index Key 0001070524  
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Fiscal Year Focus 2026  
Document Transition Report false  
Entity File Number 0-25165  
Entity Registrant Name GREENE COUNTY BANCORP, INC.  
Entity Incorporation, State or Country Code X1  
Entity Tax Identification Number 14-1809721  
Entity Address, Address Line One 302 Main Street  
Entity Address, City or Town Catskill  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 12414  
City Area Code 518  
Local Phone Number 943-2600  
Title of 12(b) Security Common Stock, $0.10 par value  
Trading Symbol GCBC  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Accelerated Filer  
Entity Emerging Growth Company false  
Entity Small Business true  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   17,025,485
Amendment Flag false  
Document Fiscal Period Focus Q3  
Current Fiscal Year End Date --06-30