Accounting Policies, by Policy (Policies)	6 Months Ended
Dec. 31, 2024
Summary of Significant Accounting Policies [Abstract]
Principles of Consolidation and Basis of Presentation	Principles of Consolidation and Basis of Presentation Within the accompanying unaudited interim consolidated financial statements and related notes to the consolidated financial statements, the June 30, 2024 data was derived from the audited consolidated financial statements and notes of Greene County Bancorp, Inc. (the “Company”) and its wholly owned subsidiaries, the Bank of Greene County (the “Bank”) and the Bank’s wholly owned subsidiaries, Greene County Commercial Bank (the “Commercial Bank”) and Greene Property Holdings, Ltd. The interim consolidated financial statements at and for the three and six months ended December 31, 2024 and 2023 are unaudited. The unaudited interim consolidated financial statements include the accounts of certain Variable Interest Entities (“VIE(s)”). In accordance with the applicable accounting guidance for consolidations, the Company consolidates a VIE if it has (i) a variable interest in the entity; (ii) the power to direct activities of the VIE that most significantly affect the entity’s economic performance; and (iii) the obligation to absorb losses of the entity or the right to receive benefits from the entity that could potentially be significant to the VIE (i.e., we are considered to be the primary beneficiary). The Company uses the equity method to account for unconsolidated investments in VIEs if it has significant influence over the entity’s operating and financing decision. Unconsolidated investments in VIEs in which the Company does not have significant influence, are carried at a cost measurement alternative. See Note 14, Variable Interest Entities for information on our involvement with VIEs. The financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 8 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. To the extent that information and notes required by GAAP for complete financial statements are contained in or are consistent with the audited financial statements incorporated by reference to Greene County Bancorp, Inc.’s Annual Report on Form 10-K for the year ended June 30, 2024, such information and notes have not been duplicated herein. In the opinion of management, all adjustments (consisting of only normal recurring items) necessary for a fair presentation of the financial position and results of operations and cash flows at and for the periods presented have been included. Certain previous years’ amounts in the unaudited consolidated financial statements and notes thereto, have been reclassified to conform to the current year’s presentation. All material inter-company accounts and transactions have been eliminated in the consolidation. The results of operations and other data for the three and six months ended December 31, 2024 are not necessarily indicative of results that may be expected for the entire fiscal year ending June 30, 2025. These consolidated financial statements consider events that occurred through the date the consolidated financial statements were issued and should be read in conjunction with the audited consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K.
Nature of Operations	Nature of Operations The Company’s primary business is the ownership and operation of its subsidiaries. At December 31, 2024, the Bank has 18 full-service offices, lending centers, an operations center, customer call center, and wealth management center, located in its market area consisting of the Hudson Valley and Capital District Regions of New York State. The Bank is primarily engaged in the business of attracting deposits from the general public in the Bank’s market area, and investing such deposits, together with other sources of funds, in loans and investment securities. The Commercial Bank’s primary business is to attract deposits from, and provide banking services to, local municipalities. Greene Property Holdings, Ltd. was formed as a New York corporation that has elected under the Internal Revenue Code to be a real estate investment trust. Currently, certain mortgages and loan notes held by the Bank are transferred and beneficially owned by Greene Property Holdings, Ltd. The Bank continues to service these loans.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could materially differ from those estimates. Material estimates that are particularly susceptible to significant change in the near term relate to the determination of the allowance for credit losses (“ACL”) on loans and on unfunded commitments.
Accrued Interest Receivable	Accrued Interest Receivable Accrued interest receivable balances are presented separately on the consolidated statements of financial condition and are not included in amortized cost when determining the allowance for credit losses. Accrued interest receivable that is deemed uncollectible is written off timely. For loans, write off typically occurs upon becoming over 90 to 120 days past due and therefore, the amount of such write offs are immaterial. Historically, the Company has not experienced uncollectible accrued interest receivable on investment securities.
Income Taxes	Income Taxes The Company uses the proportional amortization method for solar tax credit investments, whereby the associated tax credits are recognized as a reduction to tax expense. Certain federal tax credits that are non-refundable and transferable under applicable regulations are accounted for as government grants and recorded as a reduction to the amortized cost or net investment in the applicable asset generating the credit, generally within “other assets.” Amounts are amortized through depreciation or as an adjustment to yield over the estimated life of the asset. Any gain or loss on the transfer of a tax credit is recorded within “other income.”
Recently Adopted Accounting Standards and Accounting Standards Issued Not Yet Adopted	Recently Adopted Accounting Standards In March 2023, the FASB issued ASU 2023-02, Investments – Equity Method and Joint Ventures (Topic 323), Accounting for Investments in Tax Credit Structures using the Proportional Amortization Method, which permits reporting entities to elect to account for their tax equity investments, regardless of their tax credit program from which the income tax credits are received. The election can be made for each qualifying tax credit investment. Under the proportional amortization method, the initial cost of an investment is amortized in proportion to the amount of tax credits and other tax benefits received, with the amortization and tax credits recognized as a component of income tax expense. To qualify for the proportional amortization method, all of the following conditions must be met: (1) It is probable that the income tax credits allocated to the tax equity investor will be available; (2) The tax equity investor does not have the ability to excise significant influence over the operating and financial policies of the underlying project; (3) Substantially all of the projected benefits are from income tax credits and other income tax benefits; (4) The tax equity investor’s projected yield is based solely on the cash flows from the income tax credits and other income tax benefits is positive; and (5) The tax equity investor is a limited liability investor in the limited liability entity for legal and tax purposes, and the tax equity investor’s liability is limited to its capital investment. A reporting entity that applies the proportional amortization method to qualifying tax equity investments must account for the receipt of the investment tax credits using the flow-through method under Topic 740, Income Taxes. The amendments also require the application of the delayed equity contribution guidance to all tax equity investments, and require specific disclosures that must be applied to all investments that generate income tax credits and other income tax benefits from a tax credit program for which the entity has elected to apply the proportional amortization method in accordance with Subtopic 323-740. Under the proportional amortization method, the investment shall be tested for impairment when events or changes in circumstances indicate that is more likely than not that the carrying amount of the investment will not be realized. An impairment loss shall be measured as the amount by which the carrying amount of the investment exceeds its fair value. A previously recognized impairment loss shall not be reversed. The Company adopted ASU 2023-02 during the quarter ended September 30, 2024. The Company’s adoption of this standard did not have a material impact on the consolidated financial statements. Accounting Standards Issued Not Yet Adopted In October 2023, the FASB issued ASU 2023-06, Disclosure Improvements, which amends the disclosure or presentation requirements related to various subtopics in the FASB Accounting Standards Codification. The ASU was issued in response to the SEC’s August 2018 final rule that updated and simplified disclosure requirements that the SEC believed were redundant, duplicative, overlapping, outdated, or superseded. The new guidance is intended to align GAAP requirements with those of the SEC. The ASU will become effective on the earlier of the date on which the SEC removes its disclosure requirements for the related disclosure or June 30, 2027. Early adoption is not permitted. The Company’s adoption of this standard is not expected to have a material impact on the consolidated financial statements. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280), Improvements to Reportable Segment Disclosures, to improve the reportable segment disclosures by requiring disclosure of incremental segment information on an annual and interim basis. In addition, the amendments will enhance interim disclosure requirements, clarify circumstances in which an entity can disclose multiple segment measures of profit or loss provide new segment disclosure requirements for entities with a single reportable segment and contain other disclosure requirements. The amendments in this ASU are effective for annual periods beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The Company’s adoption of this standard is not expected to have a material impact on the consolidated financial statements. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740), Improvements to Income Tax Disclosures, which will require public entities to disclose annually a tabular rate reconciliation, including specific items such as state and local income tax, tax credits, nontaxable or nondeductible items, among others, and a separate disclosure requiring disaggregation of reconciling items as described above which equal or exceed 5% of the product of multiplying income from continuing operations by the applicable statutory income tax rate. The ASU is effective for annual periods beginning after December 31, 2024. The Company’s adoption of this standard is not expected to have a material impact on the consolidated financial statements.
Federal Home Loan Bank Stock	Federal Home Loan Bank Stock Federal law requires a member institution of the Federal Home Loan Bank (“FHLB”) system to hold stock of its district FHLB according to a predetermined formula. This stock is restricted in that it can only be sold to the FHLB or to another member institution, and all sales of FHLB stock must be at par. As a result of these restrictions, FHLB stock is carried at cost. FHLB stock is held as a long-term investment and its value is determined based on the ultimate recoverability of the par value. Estimated credit loss of this investment is evaluated quarterly and is a matter of judgment that reflects management’s view of the FHLB’s long-term performance, which includes factors such as the following: its operating performance; the severity and duration of declines in the fair value of its net assets related to its capital stock amount; its commitment to make payments required by law or regulation and the level of such payments in relation to its operating performance; the impact of legislative and regulatory changes on the FHLB, and accordingly, on the members of the FHLB; and its liquidity and funding position. After evaluating these considerations, the Company concluded that the par value of its investment in FHLB stock will be recovered and, therefore, no credit loss was recorded during the three and six months ended December 31, 2024 or 2023.

Accounting Policies, by Policy (Policies)

6 Months Ended

Dec. 31, 2024

Summary of Significant Accounting Policies [Abstract]

Principles of Consolidation and Basis of Presentation

Within the accompanying unaudited interim consolidated financial statements and related notes to the consolidated financial statements, the June 30, 2024 data was derived from the audited consolidated financial statements and notes of Greene County Bancorp, Inc. (the “Company”) and its wholly owned subsidiaries, the Bank of Greene County (the “Bank”) and the Bank’s wholly owned subsidiaries, Greene County Commercial Bank (the “Commercial Bank”) and Greene Property Holdings, Ltd. The interim consolidated financial statements at and for the three and six months ended December 31, 2024 and 2023 are unaudited.

The unaudited interim consolidated financial statements include the accounts of certain Variable Interest Entities (“VIE(s)”). In accordance with the applicable accounting guidance for consolidations, the Company consolidates a VIE if it has (i) a variable interest in the entity; (ii) the power to direct activities of the VIE that most significantly affect the entity’s economic performance; and (iii) the obligation to absorb losses of the entity or the right to receive benefits from the entity that could potentially be significant to the VIE (i.e., we are considered to be the primary beneficiary).

The Company uses the equity method to account for unconsolidated investments in VIEs if it has significant influence over the entity’s operating and financing decision. Unconsolidated investments in VIEs in which the Company does not have significant influence, are carried at a cost measurement alternative. See Note 14, Variable Interest Entities for information on our involvement with VIEs.

The financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 8 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. To the extent that information and notes required by GAAP for complete financial statements are contained in or are consistent with the audited financial statements incorporated by reference to Greene County Bancorp, Inc.’s Annual Report on Form 10-K for the year ended June 30, 2024, such information and notes have not been duplicated herein. In the opinion of management, all adjustments (consisting of only normal recurring items) necessary for a fair presentation of the financial position and results of operations and cash flows at and for the periods presented have been included. Certain previous years’ amounts in the unaudited consolidated financial statements and notes thereto, have been reclassified to conform to the current year’s presentation. All material inter-company accounts and transactions have been eliminated in the consolidation. The results of operations and other data for the three and six months ended December 31, 2024 are not necessarily indicative of results that may be expected for the entire fiscal year ending June 30, 2025. These consolidated financial statements consider events that occurred through the date the consolidated financial statements were issued and should be read in conjunction with the audited consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K.

Nature of Operations

The Company’s primary business is the ownership and operation of its subsidiaries. At December 31, 2024, the Bank has 18 full-service offices, lending centers, an operations center, customer call center, and wealth management center, located in its market area consisting of the Hudson Valley and Capital District Regions of New York State. The Bank is primarily engaged in the business of attracting deposits from the general public in the Bank’s market area, and investing such deposits, together with other sources of funds, in loans and investment securities. The Commercial Bank’s primary business is to attract deposits from, and provide banking services to, local municipalities. Greene Property Holdings, Ltd. was formed as a New York corporation that has elected under the Internal Revenue Code to be a real estate investment trust. Currently, certain mortgages and loan notes held by the Bank are transferred and beneficially owned by Greene Property Holdings, Ltd. The Bank continues to service these loans.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could materially differ from those estimates. Material estimates that are particularly susceptible to significant change in the near term relate to the determination of the allowance for credit losses (“ACL”) on loans and on unfunded commitments.

Accrued Interest Receivable

Accrued interest receivable balances are presented separately on the consolidated statements of financial condition and are not included in amortized cost when determining the allowance for credit losses. Accrued interest receivable that is deemed uncollectible is written off timely. For loans, write off typically occurs upon becoming over 90 to 120 days past due and therefore, the amount of such write offs are immaterial. Historically, the Company has not experienced uncollectible accrued interest receivable on investment securities.

Income Taxes

The Company uses the proportional amortization method for solar tax credit investments, whereby the associated tax credits are recognized as a reduction to tax expense. Certain federal tax credits that are non-refundable and transferable under applicable regulations are accounted for as government grants and recorded as a reduction to the amortized cost or net investment in the applicable asset generating the credit, generally within “other assets.” Amounts are amortized through depreciation or as an adjustment to yield over the estimated life of the asset. Any gain or loss on the transfer of a tax credit is recorded within “other income.”

Recently Adopted Accounting Standards and Accounting Standards Issued Not Yet Adopted

Recently Adopted Accounting Standards

In March 2023, the FASB issued ASU 2023-02, Investments – Equity Method and Joint Ventures (Topic 323), Accounting for Investments in Tax Credit Structures using the Proportional Amortization Method, which permits reporting entities to elect to account for their tax equity investments, regardless of their tax credit program from which the income tax credits are received. The election can be made for each qualifying tax credit investment. Under the proportional amortization method, the initial cost of an investment is amortized in proportion to the amount of tax credits and other tax benefits received, with the amortization and tax credits recognized as a component of income tax expense. To qualify for the proportional amortization method, all of the following conditions must be met: (1) It is probable that the income tax credits allocated to the tax equity investor will be available; (2) The tax equity investor does not have the ability to excise significant influence over the operating and financial policies of the underlying project; (3) Substantially all of the projected benefits are from income tax credits and other income tax benefits; (4) The tax equity investor’s projected yield is based solely on the cash flows from the income tax credits and other income tax benefits is positive; and (5) The tax equity investor is a limited liability investor in the limited liability entity for legal and tax purposes, and the tax equity investor’s liability is limited to its capital investment.

A reporting entity that applies the proportional amortization method to qualifying tax equity investments must account for the receipt of the investment tax credits using the flow-through method under Topic 740, Income Taxes. The amendments also require the application of the delayed equity contribution guidance to all tax equity investments, and require specific disclosures that must be applied to all investments that generate income tax credits and other income tax benefits from a tax credit program for which the entity has elected to apply the proportional amortization method in accordance with Subtopic 323-740.

Under the proportional amortization method, the investment shall be tested for impairment when events or changes in circumstances indicate that is more likely than not that the carrying amount of the investment will not be realized. An impairment loss shall be measured as the amount by which the carrying amount of the investment exceeds its fair value. A previously recognized impairment loss shall not be reversed. The Company adopted ASU 2023-02 during the quarter ended September 30, 2024. The Company’s adoption of this standard did not have a material impact on the consolidated financial statements.

Accounting Standards Issued Not Yet Adopted

In October 2023, the FASB issued ASU 2023-06, Disclosure Improvements, which amends the disclosure or presentation requirements related to various subtopics in the FASB Accounting Standards Codification. The ASU was issued in response to the SEC’s August 2018 final rule that updated and simplified disclosure requirements that the SEC believed were redundant, duplicative, overlapping, outdated, or superseded. The new guidance is intended to align GAAP requirements with those of the SEC. The ASU will become effective on the earlier of the date on which the SEC removes its disclosure requirements for the related disclosure or June 30, 2027. Early adoption is not permitted. The Company’s adoption of this standard is not expected to have a material impact on the consolidated financial statements.

In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280), Improvements to Reportable Segment Disclosures, to improve the reportable segment disclosures by requiring disclosure of incremental segment information on an annual and interim basis. In addition, the amendments will enhance interim disclosure requirements, clarify circumstances in which an entity can disclose multiple segment measures of profit or loss provide new segment disclosure requirements for entities with a single reportable segment and contain other disclosure requirements. The amendments in this ASU are effective for annual periods beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The Company’s adoption of this standard is not expected to have a material impact on the consolidated financial statements.

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740), Improvements to Income Tax Disclosures, which will require public entities to disclose annually a tabular rate reconciliation, including specific items such as state and local income tax, tax credits, nontaxable or nondeductible items, among others, and a separate disclosure requiring disaggregation of reconciling items as described above which equal or exceed 5% of the product of multiplying income from continuing operations by the applicable statutory income tax rate. The ASU is effective for annual periods beginning after December 31, 2024. The Company’s adoption of this standard is not expected to have a material impact on the consolidated financial statements.

Federal Home Loan Bank Stock

Federal law requires a member institution of the Federal Home Loan Bank (“FHLB”) system to hold stock of its district FHLB according to a predetermined formula. This stock is restricted in that it can only be sold to the FHLB or to another member institution, and all sales of FHLB stock must be at par. As a result of these restrictions, FHLB stock is carried at cost. FHLB stock is held as a long-term investment and its value is determined based on the ultimate recoverability of the par value. Estimated credit loss of this investment is evaluated quarterly and is a matter of judgment that reflects management’s view of the FHLB’s long-term performance, which includes factors such as the following: its operating performance; the severity and duration of declines in the fair value of its net assets related to its capital stock amount; its commitment to make payments required by law or regulation and the level of such payments in relation to its operating performance; the impact of legislative and regulatory changes on the FHLB, and accordingly, on the members of the FHLB; and its liquidity and funding position. After evaluating these considerations, the Company concluded that the par value of its investment in FHLB stock will be recovered and, therefore, no credit loss was recorded during the three and six months ended December 31, 2024 or 2023.