<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.21.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>340</ContextCount>
  <ElementCount>312</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>50</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>4</UnitCount>
  <MyReports>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>001 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ConsolidatedBalanceSheet</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>002 - Statement - Condensed Consolidated Balance Sheets (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ConsolidatedBalanceSheet_Parentheticals</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>003 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ConsolidatedIncomeStatement</Role>
      <ShortName>Condensed Consolidated Statements of Operations (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>004 - Statement - Condensed Consolidated Statements of Comprehensive Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ConsolidatedComprehensiveIncome</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>005 - Statement - Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ConsolidatedComprehensiveIncome_Parentheticals</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>006 - Statement - Consolidated Statements of Changes in Shareholders??? Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ShareholdersEquityType2or3</Role>
      <ShortName>Consolidated Statements of Changes in Shareholders??? Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>007 - Statement - Consolidated Statements of Changes in Shareholders??? Equity (Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ShareholdersEquityType2or3_Parentheticals</Role>
      <ShortName>Consolidated Statements of Changes in Shareholders??? Equity (Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>008 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ConsolidatedCashFlow</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>009 - Disclosure - Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/BasisofPresentation</Role>
      <ShortName>Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>010 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>011 - Disclosure - Investment Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/InvestmentSecurities</Role>
      <ShortName>Investment Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>012 - Disclosure - Loans Receivable</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivable</Role>
      <ShortName>Loans Receivable</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>013 - Disclosure - Disclosures About Fair Value of Assets and Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/DisclosuresAboutFairValueofAssetsandLiabilities</Role>
      <ShortName>Disclosures About Fair Value of Assets and Liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>014 - Disclosure - Other Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/OtherComprehensiveIncomeLoss</Role>
      <ShortName>Other Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>015 - Disclosure - Accounting Policies, by Policy (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/AccountingPoliciesByPolicy</Role>
      <ShortName>Accounting Policies, by Policy (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>016 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/EarningsPerShare</ParentRole>
      <Position>17</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>017 - Disclosure - Investment Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/InvestmentSecuritiesTables</Role>
      <ShortName>Investment Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/InvestmentSecurities</ParentRole>
      <Position>18</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>018 - Disclosure - Loans Receivable (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</Role>
      <ShortName>Loans Receivable (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivable</ParentRole>
      <Position>19</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>019 - Disclosure - Disclosures About Fair Value of Assets and Liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/DisclosuresAboutFairValueofAssetsandLiabilitiesTables</Role>
      <ShortName>Disclosures About Fair Value of Assets and Liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/DisclosuresAboutFairValueofAssetsandLiabilities</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>020 - Disclosure - Other Comprehensive Income (Loss) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/OtherComprehensiveIncomeLossTables</Role>
      <ShortName>Other Comprehensive Income (Loss) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/OtherComprehensiveIncomeLoss</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>022 - Disclosure - Earnings Per Share (Details) - Schedule of basic and diluted earnings per share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofbasicanddilutedearningspershareTable</Role>
      <ShortName>Earnings Per Share (Details) - Schedule of basic and diluted earnings per share</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/EarningsPerShareTables</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>023 - Disclosure - Investment Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/InvestmentSecuritiesDetails</Role>
      <ShortName>Investment Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>024 - Disclosure - Investment Securities (Details) - Schedule of gross unrealized or unrecognized gains and losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofgrossunrealizedorunrecognizedgainsandlossesTable</Role>
      <ShortName>Investment Securities (Details) - Schedule of gross unrealized or unrecognized gains and losses</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/InvestmentSecuritiesTables</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>025 - Disclosure - Loans Receivable (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableDetails</Role>
      <ShortName>Loans Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>026 - Disclosure - Loans Receivable (Details) - Schedule of loan portfolio</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofloanportfolioTable</Role>
      <ShortName>Loans Receivable (Details) - Schedule of loan portfolio</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>027 - Disclosure - Loans Receivable (Details) - Schedule of allowance for loan losses by portfolio segment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofallowanceforloanlossesbyportfoliosegmentTable</Role>
      <ShortName>Loans Receivable (Details) - Schedule of allowance for loan losses by portfolio segment</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>028 - Disclosure - Loans Receivable (Details) - Schedule of allowance for loan losses and the recorded investment in loans by portfolio</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofallowanceforloanlossesandtherecordedinvestmentinloansbyportfolioTable</Role>
      <ShortName>Loans Receivable (Details) - Schedule of allowance for loan losses and the recorded investment in loans by portfolio</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>029 - Disclosure - Loans Receivable (Details) - Schedule of impaired by class of loans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofimpairedbyclassofloansTable</Role>
      <ShortName>Loans Receivable (Details) - Schedule of impaired by class of loans</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>030 - Disclosure - Loans Receivable (Details) - Schedule of recorded investment in nonaccrual and loans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofrecordedinvestmentinnonaccrualandloansTable</Role>
      <ShortName>Loans Receivable (Details) - Schedule of recorded investment in nonaccrual and loans</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>031 - Disclosure - Loans Receivable (Details) - Schedule of principal balance outstanding in past due loans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofprincipalbalanceoutstandinginpastdueloansTable</Role>
      <ShortName>Loans Receivable (Details) - Schedule of principal balance outstanding in past due loans</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>032 - Disclosure - Loans Receivable (Details) - Schedule of analysis performed, the risk category of loans by class of loans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofanalysisperformedtheriskcategoryofloansbyclassofloansTable</Role>
      <ShortName>Loans Receivable (Details) - Schedule of analysis performed, the risk category of loans by class of loans</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>033 - Disclosure - Loans Receivable (Details) - Schedule of purchased credit impaired loans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofpurchasedcreditimpairedloansTable</Role>
      <ShortName>Loans Receivable (Details) - Schedule of purchased credit impaired loans</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>034 - Disclosure - Loans Receivable (Details) - Schedule of accretable yield, or income expected to be collected</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofaccretableyieldorincomeexpectedtobecollectedTable</Role>
      <ShortName>Loans Receivable (Details) - Schedule of accretable yield, or income expected to be collected</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/LoansReceivableTables</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>035 - Disclosure - Disclosures About Fair Value of Assets and Liabilities (Details) - Schedule of financial assets measured at fair value on a recurring basis</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleoffinancialassetsmeasuredatfairvalueonarecurringbasisTable</Role>
      <ShortName>Disclosures About Fair Value of Assets and Liabilities (Details) - Schedule of financial assets measured at fair value on a recurring basis</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/DisclosuresAboutFairValueofAssetsandLiabilitiesTables</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>036 - Disclosure - Disclosures About Fair Value of Assets and Liabilities (Details) - Schedule of foregoing methods and assumptions, the carrying value and fair value</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofforegoingmethodsandassumptionsthecarryingvalueandfairvalueTable</Role>
      <ShortName>Disclosures About Fair Value of Assets and Liabilities (Details) - Schedule of foregoing methods and assumptions, the carrying value and fair value</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/DisclosuresAboutFairValueofAssetsandLiabilitiesTables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>037 - Disclosure - Other Comprehensive Income (Loss) (Details) - Schedule of accumulated other comprehensive income (loss) balances, net of tax</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofaccumulatedothercomprehensiveincomelossbalancesnetoftaxTable</Role>
      <ShortName>Other Comprehensive Income (Loss) (Details) - Schedule of accumulated other comprehensive income (loss) balances, net of tax</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/OtherComprehensiveIncomeLossTables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="f10q0921_kentuckyfirst.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>038 - Disclosure - Other Comprehensive Income (Loss) (Details) - Schedule of other comprehensive income (loss) components and related tax effects</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.kentuckyfirstfederalbancorp.com/role/ScheduleofothercomprehensiveincomelosscomponentsandrelatedtaxeffectsTable</Role>
      <ShortName>Other Comprehensive Income (Loss) (Details) - Schedule of other comprehensive income (loss) components and related tax effects</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.kentuckyfirstfederalbancorp.com/role/OtherComprehensiveIncomeLossTables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" original="f10q0921_kentuckyfirst.htm">f10q0921_kentuckyfirst.htm</File>
    <File>f10q0921ex31-1_kentuckyfirst.htm</File>
    <File>f10q0921ex31-2_kentuckyfirst.htm</File>
    <File>f10q0921ex32-1_kentuckyfirst.htm</File>
    <File>f10q0921ex32-2_kentuckyfirst.htm</File>
    <File>kffb-20210930.xsd</File>
    <File>kffb-20210930_cal.xml</File>
    <File>kffb-20210930_def.xml</File>
    <File>kffb-20210930_lab.xml</File>
    <File>kffb-20210930_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/srt/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2021</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
