Condensed Financial Statements of Greene County Bancorp, Inc., Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities [Abstract]
Net Income	$ 24,769	$ 30,785
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Amortization of subordinated debt issuance costs	186	185
Net decrease (increase) in prepaid expenses and other assets	(430)	133
Net cash provided by operating activities	24,908	28,109
Cash flows from investing activities [Abstract]
Net cash (used in) provided by investing activities	(129,235)	661
Cash flows from financing activities [Abstract]
Payment of cash dividends	(3,240)	(2,191)
Net cash provided by financing activities	98,277	98,666
Net (decrease) increase in cash and cash equivalents	(6,050)	127,436
Parent Company [Member]
Cash flows from operating activities [Abstract]
Net Income	24,769	30,785
Adjustments to reconcile net income to net cash provided by operating activities: [Abstract]
Undistributed earnings of subsidiaries	(19,096)	(26,829)
Amortization of subordinated debt issuance costs	186	185
Net decrease (increase) in prepaid expenses and other assets	55	(29)
Net (decrease) increase in total liabilities	(27)	16
Net cash provided by operating activities	5,887	4,128
Cash flows from investing activities [Abstract]
Net cash transferred related to Greene Risk Management Inc. liquidation	0	(1,006)
Net cash (used in) provided by investing activities	0	(1,006)
Cash flows from financing activities [Abstract]
Payment of cash dividends	(3,240)	(2,191)
Net cash provided by financing activities	(3,240)	(2,191)
Net (decrease) increase in cash and cash equivalents	2,647	931
Cash and cash equivalents at beginning of year	19,822	18,891
Cash and cash equivalents at end of year	$ 22,469	$ 19,822