Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2024	Sep. 05, 2024	Dec. 31, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Period End Date	Jun. 30, 2024
Current Fiscal Year End Date	--06-30
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	FY
Document Transition Report	false
Entity File Number	0-25165
Entity Registrant Name	GREENE COUNTY BANCORP, INC.
Entity Central Index Key	0001070524
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 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	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 179,230
Entity Common Stock, Shares Outstanding		17,026,828
Auditor Firm ID	1884
Auditor Name	Bonadio & Co., LLP
Auditor Location	Pittsford, New York