Loans Receivable (Details) - USD ($)	9 Months Ended
Mar. 31, 2024	Jun. 30, 2023
Loans Receivable (Details) [Line Items]
Deferred loan costs	$ 312,000	$ 330,000
Principal amount	$ 50,000
Private mortgage insurance, percentage	97.00%
Borrow up percentage	90.00%
Loan to value ration	80.00%
Estimated value percentage	80.00%
Loans term	25 years
Nonresidential loans percentage	80.00%
Loans secured percentage	90.00%
Allowance for credit losses on unfunded commitments	$ 57,000
Foreclosure amount	1,200,000	766,000
Loans classified as TDR		1,400,000
Purchase credit discount	88,000	$ 88,000
Unfunded Commitments [Member]
Loans Receivable (Details) [Line Items]
Recovery on credit losses on loans	$ 3,000
Multi-family and Nonresidential Loans [Member]
Loans Receivable (Details) [Line Items]
Estimated value percentage	80.00%
Consumer Lending [Member]
Loans Receivable (Details) [Line Items]
Estimated value percentage	80.00%
Home Equity Loans [Member]
Loans Receivable (Details) [Line Items]
Estimated value percentage	90.00%
Long-Term Debt [Member]
Loans Receivable (Details) [Line Items]
Recovery on credit losses on loans	$ 13,000
Long-Term Debt [Member] \| Unfunded Commitments [Member]
Loans Receivable (Details) [Line Items]
Provision for credit losses	$ (16,000)

Represents the amount of allowance for credit losses on unfunded commitments.

No definition available.

Name:	kffb_AllowanceForCreditLossesOnUnfundedCommitments
Namespace Prefix:	kffb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of recovery on credit losses on loans.

+ References

No definition available.

+ Details

Name:	kffb_AllowanceForLoanAndLeaseLossRecoveryOfBadDebt
Namespace Prefix:	kffb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Borrow up percentage.

+ References

No definition available.

+ Details

Name:	kffb_BorrowUpPercentage
Namespace Prefix:	kffb_
Data Type:	dtr:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of loan to value ration.

+ References

No definition available.

+ Details

Name:	kffb_LoanToValueRation
Namespace Prefix:	kffb_
Data Type:	dtr:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	kffb_LoansReceivableDetailsLineItems
Namespace Prefix:	kffb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Loans secured percentage.

+ References

No definition available.

+ Details

Name:	kffb_LoansSecuredPercentage
Namespace Prefix:	kffb_
Data Type:	dtr:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Nonresidential loans percentage.

+ References

No definition available.

+ Details

Name:	kffb_NonresidentialLoansPercentage
Namespace Prefix:	kffb_
Data Type:	dtr:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Private mortgage insurance.

+ References

No definition available.

+ Details

Name:	kffb_PrivateMortgageInsurance
Namespace Prefix:	kffb_
Data Type:	dtr:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of provision for credit losses.

+ References

No definition available.

+ Details

Name:	kffb_ProvisionForCreditLosses
Namespace Prefix:	kffb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482949/835-30-55-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482900/835-30-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Specific incremental costs directly attributable to a proposed or actual offering of securities which are deferred at the end of the reporting period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 340
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.A)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480341/340-10-S99-1

+ Details

Name:	us-gaap_DeferredOfferingCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unamortized purchase premium (discount) on financing receivable. Excludes financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481598/310-20-45-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-4

+ Details

Name:	us-gaap_FinancingReceivableUnamortizedPurchasePremiumDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period between issuance and maturity of loan held for sale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_LoansHeldForSaleTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 20
-Name Accounting Standards Codification
-Section 40
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481628/310-20-40-7

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-11

+ Details

Name:	us-gaap_RealEstateAcquiredThroughForeclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of fair value of reporting unit in excess of carrying amount.

+ References

No definition available.

+ Details

Name:	us-gaap_ReportingUnitPercentageOfFairValueInExcessOfCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of restructured debt contingently payable based on the occurrence of future events or circumstances.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 470
-SubTopic 60
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481408/470-60-50-2

+ Details

Name:	us-gaap_TroubledDebtRestructuringDebtorSubsequentPeriodsContingentPaymentsAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=kffb_UnfundedCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=kffb_MultifamilyAndNonresidentialLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=kffb_ConsumerLendingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=kffb_HomeEquityLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_LongTermDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: