XML 209 R74.htm IDEA: XBRL DOCUMENT
v3.25.2

Employee Benefit Plans (Details) - USD ($) | 12 Months Ended
--- | ---
Jun. 30, 2025 | Jun. 30, 2024
Employee Benefit Plans [Abstract] |  |
Required age to participate in defined Benefit Plan | 21 years |
Accumulated benefit obligation for the pension plan | $ 4,100,000 | $ 4,100,000
Compensation rate for frozen plan | 0.00% |
Required service period to participate in Defined Contribution Plan | 3 months |
Equal matching of employer contribution dollar for dollar | 3.00% |
Percentage of employer contribution for next 3% | 50.00% |
Company contributions associated with the contribution plan | $ 530,000 | 520,000
Payment authorized for purchase of additional shares for ESOP | 190,000 | 180,000
ESOP expense | $ 194,000 | $ 186,000
Unearned shares (in Shares) | 0 | 0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) | $ 15,000 | $ 65,000
Short-term and Intermediate-term Fixed Income Bond Funds [Member] |  |
Employee Benefit Plans [Abstract] |  |
Target allocation for investment in mutual funds | 100.00% |
Supplemental Executive Retirement Plan [Member] |  |
Employee Benefit Plans [Abstract] |  |
Period in which lump sum benefit will be paid in the event of death, disability or termination | 2 years |
Number of annual installments in which benefit will be paid | 10 |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) | $ 2,400,000 | 2,200,000
Postemployment benefits liability | $ 17,600,000 | $ 15,200,000
Maximum [Member] |  |
Employee Benefit Plans [Abstract] |  |
Percentage of compensation allowed to be contributed by employees on pre-tax basis | 50.00% |
Maximum [Member] | Mutual Funds - Balanced [Member] |  |
Employee Benefit Plans [Abstract] |  |
Allowable variation | 5.00% |
Maximum [Member] | Supplemental Executive Retirement Plan [Member] |  |
Employee Benefit Plans [Abstract] |  |
Vesting period | 20 years |
Minimum [Member] | Supplemental Executive Retirement Plan [Member] |  |
Employee Benefit Plans [Abstract] |  |
Vesting period | 10 years |
Deferred Base Salary [Member] | Supplemental Executive Retirement Plan [Member] |  |
Employee Benefit Plans [Abstract] |  |
Maximum annual contribution per employee | 50.00% |
Deferred Annual Bonus [Member] | Supplemental Executive Retirement Plan [Member] |  |
Employee Benefit Plans [Abstract] |  |
Maximum annual contribution per employee | 100.00% |
Employee Stock Ownership Plan [Member] |  |
Employee Benefit Plans [Abstract] |  |
Award vesting period | 3 years |

X
- Definition Target allocation allowable variation percentage of investments of this type to total plan assets presented on a weighted average basis. + References No definition available. + Details
Name: | gcbc_DefinedBenefitPlanTargetPlanAssetAllocationsAllowableVariation
Namespace Prefix: | gcbc_
Data Type: | dtr:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the percentage of compensation allowed to be contributed by employees on a pre-tax basis. + References No definition available. + Details
Name: | gcbc_DefinedContributionPlanPercentageOfCompensationAllowedToBeContributedByEmployeeOnPreTaxBasis
Namespace Prefix: | gcbc_
Data Type: | dtr:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period which an employee's right to exercise an award from a defined contribution plan is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | gcbc_DefinedContributionPlanVestingPeriod
Namespace Prefix: | gcbc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Shares contributed to the ESOP that have not yet been earned. + References No definition available. + Details
Name: | gcbc_EmployeeStockOwnershipPlanESOPNumberOfUnearnedShares
Namespace Prefix: | gcbc_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the equal matching of employer contribution dollar for dollar. + References No definition available. + Details
Name: | gcbc_EqualMatchingOfEmployerContributionDollarForDollar
Namespace Prefix: | gcbc_
Data Type: | dtr:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Elements represents the compensation rate of benefit plan which is frozen by the entity. + References No definition available. + Details
Name: | gcbc_FrozenPlanCompensationRate
Namespace Prefix: | gcbc_
Data Type: | dtr:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Refers to the number of annual installments in which benefit will be paid in the event the executive is entitled to a benefit due to retirement or other termination of employment. + References No definition available. + Details
Name: | gcbc_NumberOfAnnualInstallmentsInWhichBenefitWillBePaid
Namespace Prefix: | gcbc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Payment authorized for purchase of additional shares for ESOP. + References No definition available. + Details
Name: | gcbc_PaymentAuthorizedForPurchaseOfAdditionalSharesForEsop
Namespace Prefix: | gcbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents the percentage of employer contribution for next specified percentage. + References No definition available. + Details
Name: | gcbc_PercentageOfEmployerContributionForNextSpecifiedPercentage
Namespace Prefix: | gcbc_
Data Type: | dtr:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Element presents the period in which lump sum benefit will be paid in the event of death, disability or termination, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | gcbc_PeriodInWhichLumpSumBenefitWillBePaidInEventOfDeathDisabilityOrTermination
Namespace Prefix: | gcbc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Element refers to the Required age to participate in defined benefit pension plan of the entity. + References No definition available. + Details
Name: | gcbc_RequiredAgeToParticipateInDefinedBenefitPlan
Namespace Prefix: | gcbc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Element represents the required service period after which an employee can participate in the defined contribution plan, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | gcbc_RequiredServicePeriodToParticipateInDefinedContributionPlan
Namespace Prefix: | gcbc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-5 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of net periodic benefit cost (credit) for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (q) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-5 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-6 + Details
Name: | us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 70 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480794/715-70-50-1 + Details
Name: | us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 70 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480794/715-70-50-1 + Details
Name: | us-gaap_DefinedContributionPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of plan compensation cost recognized during the period. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480489/718-40-50-1 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 718 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 20 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480459/718-40-55-20 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 718 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 9 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480459/718-40-55-9 + Details
Name: | us-gaap_EmployeeStockOwnershipPlanESOPCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The carrying amount as of the balance sheet date of the obligations recognized for the various benefits provided to former or inactive employees, their beneficiaries, and covered dependents after employment but before retirement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(15)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 712 -SubTopic 10 -Name Accounting Standards Codification -Section 25 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481179/712-10-25-4 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 712 -SubTopic 10 -Name Accounting Standards Codification -Section 25 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481179/712-10-25-5 + Details
Name: | us-gaap_PostemploymentBenefitsLiabilityCurrentAndNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=gcbc_ShortTermAndIntermediateTermSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_BalancedFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis=gcbc_DeferredBaseSalaryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis=us-gaap_DeferredBonusMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis=gcbc_EmployeeStockOwnershipPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |