Legal Entity [Axis] STATEMENTS OF NET ASSETS AVAILABLE FOR PLAN BENEFITS [Abstract] TOTAL ASSETS TOTAL LIABILITIES NET ASSETS AVAILABLE FOR PLAN BENEFITS Net assets available for benefits, beginning NET ASSETS AVAILABLE FOR PLAN BENEFITS, ENDING STATEMENTS OF CHANGES IN NET ASSETS AVAILABLE FOR PLAN BENEFITS [Abstract] Net investment income Total contributions TOTAL ADDITIONS TOTAL DEDUCTIONS Net (decrease) increase in net assets DESCRIPTION OF PLAN [Abstract] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract] PLAN TERMINATION [Abstract] PARTY-IN-INTEREST TRANSACTIONS [Abstract] FAIR VALUE MEASUREMENTS [Abstract] Investment Type [Axis] Fair Value Hierarchy and NAV [Axis] TAX STATUS [Abstract] Schedule of Assets (Held at End of Year) [Abstract] Statistical Measurement [Axis] Document Type Document Period End Date Document Fiscal Year Focus Entity Registrant Name Entity Central Index Key Amendment Flag ASSETS Investments, at fair value Investments at fair value Investment at market value Notes receivable from participants LIABILITIES Other liabilities ADDITIONS TO NET ASSETS Investment income: Interest and dividend income Interest income, notes receivable from participants Net appreciation in fair value of investments Contributions: Participant Employer Rollover DEDUCTIONS FROM NET ASSETS Benefits paid to participants Administrative expenses The Bank of Greene County Employees’ Savings and Profit Sharing Plan and Trust [Member] DESCRIPTION OF PLAN Percentage of Compensation Based on Plan Year Automatic deferral percentage, year 1 Automatic deferral percentage, year 2 Automatic deferral percentage, year 3 Automatic deferral percentage, year 4 and thereafter SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES PLAN TERMINATION PARTY-IN-INTEREST TRANSACTIONS FAIR VALUE MEASUREMENTS Plan’s Investments at Fair Value TAX STATUS Schedule of Assets (Held at End of Year) Identity of issuer, borrower, lessor, or similar party Participant-directed status Current value Party-in-interest Description of investment including maturity date, rate of interest, collateral, par, or maturity value Notes receivable from participants Notes receivable from participants, interest rate Total Investments Common Stock Fund - Employer Stock [Member] Common Stock Fund - Money Market [Member] Common Stock Fund – Money Market [Member] Self-Directed Brokerage Accounts [Member] Mutual Funds [Member] Investments in Fair Value Hierarchy [Member] Common Collective Trust Fund [member] Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Significant Other Observable Inputs (Level 2) [Member] Significant Unobservable Inputs (Level 3) [Member] Investment, Identifier [Axis] Notes Receivable from Participants [Member] Minimum [Member] Maximum [Member] EBP, Contribution, Participating Employer [Axis] Plan agreement description Employees service period for plan eligibility Minimum service hours for plan eligibility (in Hour) Company's matching contribution percentage Minimum age participants will be eligible to make catch-up contributions (in Age) Participant’s compensation percentage eligible for matching Employer contribution vesting percentage Employer contribution vesting period Minimum amount participants may borrow from their accounts (in Dollars) Maximum amount participants may borrow from their accounts (in Dollars) Maximum percentage participants may borrow from their accounts Notes receivable from participants, minimum term Notes receivable from participants, maximum term Notes receivable from participant, basis spread variable rate Non-vested participants, forfeited balance (in Dollars) Forfeitures amount used to reduce employer matching contributions (in Dollars) Number of shares or units held by the Plan (in Shares) Shares or units held by the Plan, price per share or unit (in Dollars per share) Unfunded commitments Withdrawal restrictions Increase from transfer into Level 3 Decrease from transfer out of Level 3 Tax determination opinion letter received from IRS Tax determination letter received from IRS date Tax-exempt qualified status EIN: Plan No. Plan Name Basis of Presentation Use of Estimates Risks and Uncertainties Cash Investment Valuation and Income Recognition Investment Fees Notes Receivable from Participants Participant's Contribution Eligible for 100% Matching [Member] Participant’s Contribution From 3% to 6% Eligible for 50% Matching [Member] Safe Harbor Matching Contributions [Member] Non-Safe Harbor Matching Contributions [Member] Common Stock Fund [Member] Entity [Domain] EBP, Statement of Net Asset Available for Benefit [Table] STATEMENTS OF NET ASSETS AVAILABLE FOR PLAN BENEFITS [Abstract] EBP, Statement of Change in Net Asset Available for Benefit [Table] STATEMENTS OF CHANGES IN NET ASSETS AVAILABLE FOR PLAN BENEFITS [Abstract] EBP, Description of Plan [Table] DESCRIPTION OF PLAN [Abstract] EBP, Accounting Policy [Table] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract] EBP, Plan Termination [Table] PLAN TERMINATION [Abstract] EBP, Related Party and Party-in-Interest Transactions [Table] PARTY-IN-INTEREST TRANSACTIONS [Abstract] EBP, Investment, Fair Value and NAV [Table] FAIR VALUE MEASUREMENTS [Abstract] EBP, Tax Status [Table] TAX STATUS [Abstract] EBP, Schedule of Asset Held for Investment [Table] Schedule of Assets (Held at End of Year) [Abstract] EBP, Accounting Policy [Line Items] Investments [Domain] Fair Value Hierarchy and NAV [Domain] Statistical Measurement [Domain] EBP, Contribution, Participating Employer [Domain] Disclosure of accounting policy for cash held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Amount of increase in net asset available for benefit from interest income on note receivable from participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee service period required to be eligible to participate in the employee benefit plan under the terms of the employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employee Benefit Plan, Sponsor's matching contribution vesting percentage upon certain number of years of employment conditions as defined by the employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Employer contribution vesting period, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Amount of withdrawal restrictions for investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), that is fair value measured at net asset value (NAV) per share as practical expedient. Minimum number of hours an employee is required to work in order to become eligible to participate in the employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Percentage added to reference rate used to compute variable rate on loans receivable from participants in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Period of repayment of loan, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Period of repayment of loan, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Percentage of eligible compensation contributed for participant automatically enrolled in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) during year four and thereafter. Percentage of eligible compensation contributed for participant automatically enrolled in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) during year one. Percentage of eligible compensation contributed for participant automatically enrolled in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) during year three. Percentage of eligible compensation contributed for participant automatically enrolled in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) during year two. The age at which participants become eligible for contributions under employee benefit plan. Plan number of employee stock purchase, saving, or similar plan (employee benefit plan (EBP). Non-safe harbor is an employer matching contribution to employee benefit plan that does not meet the IRS safe harbor requirements. Safe harbor is an employer matching contribution to employee benefit plan that meets IRS safe harbor rules. Participant-Directed Investments [Member] Mutual Fund [Member] LSV Value Equity [Member] Self-Directed Brokerage Accounts [Member] Vanguard Target Retirement 2040 Inv. [Member] T. Rowe Price Blue Chip Growth [Member] Vanguard Inflation-Protected Secs Adm [Member] Vanguard 500 Index Admiral [Member] Vanguard Target Retirement 2055 Inv. [Member] American Funds Europacific GR R6 [Member] Common Stock Fund- Employer Stock [Member] MFS Massachusetts Investors TR R6 [Member] Vanguard Mid Cap Index Adm [Member] Money Market Account [Member] Vanguard Target Retirement 2070 Inv. [Member] Reliance Trust Company Stable Value Collective Trust - Series 25053 [Member] Vanguard Target Retirement 2020 Inv. [Member] Dodge & Cox Income [Member] Vanguard Target Retirement 2045 Inv. [Member] Vanguard Target Retirement Income Inv [Member] Vanguard Target Retirement 2035 Inv. [Member] Vanguard Target Retirement 2060 Inv. [Member] Greene County Bancorp, Inc. Common Stock [Member] Vanguard Small Cap Index Adm [Member] Common Collective Trust Fund [Member] Vanguard Target Retirement 2065 Inv. [Member] Invesco Global Fund R6 [Member] Vanguard Target Retirement 2025 Inv. [Member] Vanguard Value Index Adm [Member] Qualified Plan [Member] Vanguard Target Retirement 2050 Inv. [Member] Vanguard Target Retirement 2030 Inv. [Member] Federated Government Obligation Fund [Member] Investments In Fair Value Hierarchy Member EBP, Employer, Common Stock Fund [Member] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Employer, Common Stock [Member] EBP, Employer Contribution, Participant Compensation Matched, Percentage Fair Value, Inputs, Level 3 [Member] Employee Benefit Plan Participant Minimum Age Eligible To Make Catch Up Contributions Money Market Funds [Member] EBP, Tax Qualification Status [Extensible Enumeration] EBP, Employer Contribution, Matching Percentage EBP, Plan Number EBP, Risk and Uncertainty [Policy Text Block] EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] EBP, Self-Directed Brokerage Account [Member] Employee Benefit Plan Employer Contribution Vesting Percentage Employee Benefit Plan Participant Contribution Automatic Deferral Rate Year Four And Thereafter EBP, Note Receivable from Participant [Policy Text Block] EBP, Investment, Fair Value and NAV [Table Text Block] EBP, Related Party and Party-in-Interest Transactions [Text Block] EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount Employee Benefit Plan Plan Termination Line Items EBP, Description, Available [true false] EBP, Investment, Level 3 Reconciliation, Decrease from Transfer out of Level 3 EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment EBP, Expense [Policy Text Block] EBP, Related Party and Party-in-Interest Transactions [Line Items] EBP002 Member Safe Harbor Matching Contribution Member Fair Value, Inputs, Level 1 [Member] EBP, Change in Net Asset Available for Benefit, Increase EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense EBP, Summary of Accounting Policy [Text Block] EBP, Tax Status [Text Block] EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Employee Benefit Plan Participant Contribution Automatic Deferral Rate Year One EBP, Note Receivable from Participant Employee Benefit Plan Note Receivable From Participant Account Maximum Borrowing Term EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant EBP, Change in Net Asset Available for Benefit, Increase from Contribution Participants Contribution Eligible For100 Matching Member EBP, Liability EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount EBP, Investment, Current Value, Type [Extensible Enumeration] EBP, Asset [Abstract] EBP, Use of Estimate [Policy Text Block] EBP, Asset Common Collective Trust [Member] EBP, Change in Net Asset Available for Benefit, Increase [Abstract] Employee Benefit Plan Participant Contribution Automatic Deferral Rate Year Three EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution EBP, Description of Plan [Text Block] Document Fiscal Year Focus Employee Benefit Plan Employer Contribution Vesting Period Employee Benefit Plan Note Receivable From Participant Account Minimum Borrowing Term EBP, Tax Determination Letter, Date EBP, Asset Held for Investment, Participant Loan, Interest Rate Employee Benefit Plan Cash Policy Text Block EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage EBP, Forfeited Nonvested Account Minimum [Member] EBP, Investment, Issuer Name [Extensible Enumeration] EBP, Plan Termination [Text Block] EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Investment, Number of Shares EBP, Description of Plan [Line Items] Employee Benefit Plan Change In Net Asset Available For Benefit Interest Income On Notes Receivable From Participants EBP, Asset Held for Investment, Party-in-Interest [true false] EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash Fair Value, Inputs, Level 2 [Member] Employee Benefit Plan Note Receivable From Participant Account Basis Spread Variable Rate Employee Benefit Plan Minimum Service Hours Required To Be Eligible To Participate In Plan Employee Benefit Plan Employee Eligibility Service Period Required To Participate In Plan EBP, Change in Net Asset Available for Benefit, Decrease EBP, Basis of Accounting [Policy Text Block] EBP, Investment, Fair Value and NAV [Line Items] EBP, Liability [Abstract] EBP, Asset Held for Investment Employee Benefit Plan Participant Contribution Automatic Deferral Rate Year Two Employee Benefit Plan Fair Value Investment NAVWithdrawal Restrictions EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Net Asset Available for Benefit EBP, Investment [Policy Text Block] Maximum [Member] EBP, Schedule of Asset Held for Investment [Line Items] Document Type EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment EBP, Investment, Level 3 Reconciliation, Increase from Transfer into Level 3 Entity Tax Identification Number Amendment Flag Notes Receivable From Participants Member EBP, Tax Status [Line Items] Document Period End Date EBP, Other Liability EBP, Investment, Fair Value and NAV [Text Block] EBP, Contribution [Table Text Block] EBP, Schedule of Asset Held for Investment [Table Text Block] Non Safe Harbor Matching Contribution Member Entity Central Index Key EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value EBP, Fair Value, Investment, NAV, Unfunded Commitment EBP, Net Asset Value per Share or Unit Investment, Identifier [Axis] EBP, Forfeited Nonvested Account, Decrease from Employer Contribution EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover EBP, Plan Name Entity Registrant Name Participants Contribution From3 To6 Eligible For50 Matching Member EBP, Change in Net Asset Available for Benefit, Increase (Decrease) EBP, Tax Determination Letter, Obtained [true false]