<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.23.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>1359</ContextCount>
  <ElementCount>568</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>179</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000100 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>000200 - Statement - CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/CONSOLIDATEDSTATEMENTSOFFINANCIALCONDITION</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>000300 - Statement - CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/CONSOLIDATEDSTATEMENTSOFFINANCIALCONDITIONParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>000400 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/CONSOLIDATEDSTATEMENTSOFINCOME</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>000500 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSS</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>000600 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>000700 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>000705 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITYParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>010001 - Disclosure - BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/BASISOFPRESENTATIONANDSIGNIFICANTACCOUNTINGPOLICIES</Role>
      <ShortName>BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>010005 - Disclosure - DEBT SECURITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEBTSECURITIES</Role>
      <ShortName>DEBT SECURITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>010008 - Disclosure - LOANS HELD FOR INVESTMENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENT</Role>
      <ShortName>LOANS HELD FOR INVESTMENT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>010009 - Disclosure - ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LEASES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ALLOWANCEFORCREDITLOSSESFORLOANSANDFINANCELEASES</Role>
      <ShortName>ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LEASES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>010011 - Disclosure - OTHER REAL ESTATE OWNED</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/OTHERREALESTATEOWNED</Role>
      <ShortName>OTHER REAL ESTATE OWNED</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>010014 - Disclosure - GOODWILL AND OTHER INTANGIBLES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/GOODWILLANDOTHERINTANGIBLES</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>010015 - Disclosure - NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETS</Role>
      <ShortName>NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>010016 - Disclosure - DEPOSITS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEPOSITS</Role>
      <ShortName>DEPOSITS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>010017 - Disclosure - SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTS</Role>
      <ShortName>SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>010018 - Disclosure - ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ADVANCESFROMTHEFEDERALHOMELOANBANKFHLB</Role>
      <ShortName>ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>010020 - Disclosure - OTHER LONG-TERM BORROWINGS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/OTHERLONGTERMBORROWINGS</Role>
      <ShortName>OTHER LONG-TERM BORROWINGS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>010021 - Disclosure - EARNINGS PER COMMON SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/EARNINGSPERCOMMONSHARE</Role>
      <ShortName>EARNINGS PER COMMON SHARE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>010022 - Disclosure - STOCK-BASED COMPENSATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATION</Role>
      <ShortName>STOCK-BASED COMPENSATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>010023 - Disclosure - STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKHOLDERSEQUITY</Role>
      <ShortName>STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>010024 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSS</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE LOSS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>010025 - Disclosure - EMPLOYEE BENEFIT PLANS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/EMPLOYEEBENEFITPLANS</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>010028 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/INCOMETAXES</Role>
      <ShortName>INCOME TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>010032 - Disclosure - FAIR VALUE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/FAIRVALUE</Role>
      <ShortName>FAIR VALUE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>010033 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERS</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>010034 - Disclosure - SEGMENT INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SEGMENTINFORMATION</Role>
      <ShortName>SEGMENT INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>010035 - Disclosure - SUPPLEMENTAL STATEMENT OF CASH FLOWS INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SUPPLEMENTALSTATEMENTOFCASHFLOWSINFORMATION</Role>
      <ShortName>SUPPLEMENTAL STATEMENT OF CASH FLOWS INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>010036 - Disclosure - REGULATORY MATTERS, COMMITMENTS, AND CONTINGENCIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/REGULATORYMATTERSCOMMITMENTSANDCONTINGENCIES</Role>
      <ShortName>REGULATORY MATTERS, COMMITMENTS, AND CONTINGENCIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>010037 - Disclosure - FIRST BANCORP. (Holding Company Only) Financial Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/FIRSTBANCORPHoldingCompanyOnlyFinancialInformation</Role>
      <ShortName>FIRST BANCORP. (Holding Company Only) Financial Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>020000 - Disclosure - BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/BASISOFPRESENTATIONANDSIGNIFICANTACCOUNTINGPOLICIESPolicies</Role>
      <ShortName>BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>030005 - Disclosure - DEBT SECURITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEBTSECURITIESTables</Role>
      <ShortName>DEBT SECURITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/DEBTSECURITIES</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>030008 - Disclosure - LOANS HELD FOR INVESTMENT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTTables</Role>
      <ShortName>LOANS HELD FOR INVESTMENT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENT</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>030009 - Disclosure - ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LEASES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ALLOWANCEFORCREDITLOSSESFORLOANSANDFINANCELEASESTables</Role>
      <ShortName>ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LEASES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/ALLOWANCEFORCREDITLOSSESFORLOANSANDFINANCELEASES</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>030011 - Disclosure - OTHER REAL ESTATE OWNED (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/OTHERREALESTATEOWNEDTables</Role>
      <ShortName>OTHER REAL ESTATE OWNED (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/OTHERREALESTATEOWNED</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>030014 - Disclosure - GOODWILL AND OTHER INTANGIBLES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/GOODWILLANDOTHERINTANGIBLESTables</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/GOODWILLANDOTHERINTANGIBLES</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>030015 - Disclosure - NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSTables</Role>
      <ShortName>NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETS</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>030016 - Disclosure - DEPOSITS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEPOSITSTables</Role>
      <ShortName>DEPOSITS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/DEPOSITS</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>030018 - Disclosure - SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSTables</Role>
      <ShortName>SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTS</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>030019 - Disclosure - ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ADVANCESFROMTHEFEDERALHOMELOANBANKFHLBTables</Role>
      <ShortName>ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/ADVANCESFROMTHEFEDERALHOMELOANBANKFHLB</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>030020 - Disclosure - OTHER LONG-TERM BORROWINGS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/OTHERLONGTERMBORROWINGSTables</Role>
      <ShortName>OTHER LONG-TERM BORROWINGS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/OTHERLONGTERMBORROWINGS</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>030021 - Disclosure - EARNINGS PER COMMON SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/EARNINGSPERCOMMONSHARETables</Role>
      <ShortName>EARNINGS PER COMMON SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/EARNINGSPERCOMMONSHARE</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>030022 - Disclosure - STOCK-BASED COMPENSATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATIONTables</Role>
      <ShortName>STOCK-BASED COMPENSATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATION</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>030023 - Disclosure - STOCKHOLDERS' EQUITY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKHOLDERSEQUITYTables</Role>
      <ShortName>STOCKHOLDERS' EQUITY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/STOCKHOLDERSEQUITY</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>030024 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSSTables</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSS</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>030025 - Disclosure - EMPLOYEE BENEFIT PLANS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/EMPLOYEEBENEFITPLANSTables</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/EMPLOYEEBENEFITPLANS</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>030030 - Disclosure - FAIR VALUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/FAIRVALUETables</Role>
      <ShortName>FAIR VALUE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/FAIRVALUE</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>030031 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSTables</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERS</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>030033 - Disclosure - SEGMENT INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SEGMENTINFORMATIONTables</Role>
      <ShortName>SEGMENT INFORMATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/SEGMENTINFORMATION</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>030034 - Disclosure - SUPPLEMENTAL STATEMENT OF CASH FLOWS INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SUPPLEMENTALSTATEMENTOFCASHFLOWSINFORMATIONTables</Role>
      <ShortName>SUPPLEMENTAL STATEMENT OF CASH FLOWS INFORMATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/SUPPLEMENTALSTATEMENTOFCASHFLOWSINFORMATION</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>030035 - Disclosure - REGULATORY MATTERS, COMMITMENTS, AND CONTINGENCIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/REGULATORYMATTERSCOMMITMENTSANDCONTINGENCIESTables</Role>
      <ShortName>REGULATORY MATTERS, COMMITMENTS, AND CONTINGENCIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/REGULATORYMATTERSCOMMITMENTSANDCONTINGENCIES</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>030037 - Disclosure - FIRST BANCORP. (Holding Company Only) Financial Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/FIRSTBANCORPHoldingCompanyOnlyFinancialInformationTables</Role>
      <ShortName>FIRST BANCORP. (Holding Company Only) Financial Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/FIRSTBANCORPHoldingCompanyOnlyFinancialInformation</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>040012 - Disclosure - BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Adoption of new Accounting Pronouncements (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/BASISOFPRESENTATIONANDSIGNIFICANTACCOUNTINGPOLICIESAdoptionOfNewAccountingPronouncementsDetail</Role>
      <ShortName>BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Adoption of new Accounting Pronouncements (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>040300 - Disclosure - DEBT SECURITIES - Investment Securities Available for Sale (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEBTSECURITIESInvestmentSecuritiesAvailableForSaleDetail</Role>
      <ShortName>DEBT SECURITIES - Investment Securities Available for Sale (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>040302 - Disclosure - DEBT SECURITIES - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEBTSECURITIESAdditionalInformationDetail</Role>
      <ShortName>DEBT SECURITIES - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>040303 - Disclosure - DEBT SECURITIES - Available-For-Sale Investments' Fair Value And Gross Unrealized Losses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEBTSECURITIESAvailableForSaleInvestmentsFairValueAndGrossUnrealizedLossesDetail</Role>
      <ShortName>DEBT SECURITIES - Available-For-Sale Investments' Fair Value And Gross Unrealized Losses (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>040360 - Disclosure - DEBT SECURITIES - ACL for Debt Securities Available-for-Sale (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEBTSECURITIESACLForDebtSecuritiesAvailableforSaleDetail</Role>
      <ShortName>DEBT SECURITIES - ACL for Debt Securities Available-for-Sale (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>040380 - Disclosure - DEBT SECURITIES - Investment Securities Held to Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEBTSECURITIESInvestmentSecuritiesHeldToMaturityDetail</Role>
      <ShortName>DEBT SECURITIES - Investment Securities Held to Maturity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>040385 - Disclosure - DEBT SECURITIES - Investments Securities Held to Maturity (Securities in continuous unrealized loss position) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEBTSECURITIESInvestmentsSecuritiesHeldToMaturitySecuritiesInContinuousUnrealizedLossPositionDetail</Role>
      <ShortName>DEBT SECURITIES - Investments Securities Held to Maturity (Securities in continuous unrealized loss position) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>040390 - Disclosure - DEBT SECURITIES - ACL on Debt Securities Held-To-Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEBTSECURITIESACLOnDebtSecuritiesHeldToMaturityDetail</Role>
      <ShortName>DEBT SECURITIES - ACL on Debt Securities Held-To-Maturity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>040600 - Disclosure - LOANS HELD FOR INVESTMENT - Loan Portfolio Held for Investment (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTLoanPortfolioHeldForInvestmentDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Loan Portfolio Held for Investment (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>040610 - Disclosure - LOANS HELD FOR INVESTMENT - Loan Portfolio Held for Investment (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTLoanPortfolioHeldForInvestmentParentheticalDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Loan Portfolio Held for Investment (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>040800 - Disclosure - LOANS HELD FOR INVESTMENT - Corporation's Aging of Loans Held for Investment Portfolio (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTCorporationsAgingOfLoansHeldForInvestmentPortfolioDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Corporation's Aging of Loans Held for Investment Portfolio (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>040850 - Disclosure - LOANS HELD FOR INVESTMENT - Corporation's Aging of Loans Held for Investment Portfolio (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTCorporationsAgingOfLoansHeldForInvestmentPortfolioParentheticalDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Corporation's Aging of Loans Held for Investment Portfolio (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>040900 - Disclosure - LOANS HELD FOR INVESTMENT - Corporation's Commercial and Construction Loans by Portfolio Classes and by Origination Year Based on the Internal Credit Risk Category (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTCorporationsCommercialAndConstructionLoansByPortfolioClassesAndByOriginationYearBasedOnTheInternalCreditRiskCategoryDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Corporation's Commercial and Construction Loans by Portfolio Classes and by Origination Year Based on the Internal Credit Risk Category (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>040925 - Disclosure - LOANS HELD FOR INVESTMENT - Corporation's Residential Mortgage Loans By Origination Year Based on Accrual Status (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTCorporationsResidentialMortgageLoansByOriginationYearBasedOnAccrualStatusDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Corporation's Residential Mortgage Loans By Origination Year Based on Accrual Status (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>040975 - Disclosure - LOANS HELD FOR INVESTMENT - Corporation's Consumer Loans by Origination Year Based on Accrual Status (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTCorporationsConsumerLoansByOriginationYearBasedOnAccrualStatusDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Corporation's Consumer Loans by Origination Year Based on Accrual Status (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>040980 - Disclosure - LOANS HELD FOR INVESTMENT - Collateral Dependent Loans Individually Evaluated For Purposes of Determining the ACL (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTCollateralDependentLoansIndividuallyEvaluatedForPurposesOfDeterminingTheACLDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Collateral Dependent Loans Individually Evaluated For Purposes of Determining the ACL (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>041100 - Disclosure - LOANS HELD FOR INVESTMENT - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTAdditionalInformationDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>041400 - Disclosure - LOANS HELD FOR INVESTMENT - Selected Information on TDRs includes Recorded Investment by Loan Class and Modification Type (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTSelectedInformationOnTDRsIncludesRecordedInvestmentByLoanClassAndModificationTypeDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Selected Information on TDRs includes Recorded Investment by Loan Class and Modification Type (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>041410 - Disclosure - LOANS HELD FOR INVESTMENT - Financial Effects of the Permanent Modifications Granted to Borrowers Experiencing Financial Difficulty (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTFinancialEffectsOfThePermanentModificationsGrantedToBorrowersExperiencingFinancialDifficultyDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Financial Effects of the Permanent Modifications Granted to Borrowers Experiencing Financial Difficulty (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>041420 - Disclosure - LOANS HELD FOR INVESTMENT - Performance of Loans Modified During Period (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/LOANSHELDFORINVESTMENTPerformanceOfLoansModifiedDuringPeriodDetail</Role>
      <ShortName>LOANS HELD FOR INVESTMENT - Performance of Loans Modified During Period (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>041800 - Disclosure - ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LOSSES - Activity in ACL on loans and finance leases (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ALLOWANCEFORCREDITLOSSESFORLOANSANDFINANCELOSSESActivityInACLOnLoansAndFinanceLeasesDetail</Role>
      <ShortName>ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LOSSES - Activity in ACL on loans and finance leases (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>041845 - Disclosure - ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LEASES - Carrying Amount of Portfolios (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ALLOWANCEFORCREDITLOSSESFORLOANSANDFINANCELEASESCarryingAmountOfPortfoliosDetail</Role>
      <ShortName>ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LEASES - Carrying Amount of Portfolios (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>041860 - Disclosure - ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LOSSES - Activity in ACL for unfunded loan commitments and standby letters of credit (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ALLOWANCEFORCREDITLOSSESFORLOANSANDFINANCELOSSESActivityInACLForUnfundedLoanCommitmentsAndStandbyLettersOfCreditDetail</Role>
      <ShortName>ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LOSSES - Activity in ACL for unfunded loan commitments and standby letters of credit (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>041870 - Disclosure - ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LEASES - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ALLOWANCEFORCREDITLOSSESFORLOANSANDFINANCELEASESAdditionalInformationDetail</Role>
      <ShortName>ALLOWANCE FOR CREDIT LOSSES FOR LOANS AND FINANCE LEASES - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>041955 - Disclosure - OTHER REAL ESTATE OWNED- Other real estate owned (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/OTHERREALESTATEOWNEDOtherRealEstateOwnedDetail</Role>
      <ShortName>OTHER REAL ESTATE OWNED- Other real estate owned (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>041956 - Disclosure - OTHER REAL ESTATE OWNED- Additional information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/OTHERREALESTATEOWNEDAdditionalInformationDetail</Role>
      <ShortName>OTHER REAL ESTATE OWNED- Additional information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>042000 - Disclosure - GOODWILL AND OTHER INTANGIBLES - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureGOODWILLANDOTHERINTANGIBLESAdditionalInformationDetail</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>042050 - Disclosure - GOODWILL AND OTHER INTANGIBLES - Gross Amount and Accumulated Amortization of Other Intangible Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureGOODWILLANDOTHERINTANGIBLESGrossAmountAndAccumulatedAmortizationOfOtherIntangibleAssetsDetail</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES - Gross Amount and Accumulated Amortization of Other Intangible Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>042052 - Disclosure - GOODWILL AND OTHER INTANGIBLES - Amortization Expense (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/GOODWILLANDOTHERINTANGIBLESAmortizationExpenseDetail</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES - Amortization Expense (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>042100 - Disclosure - NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSAdditionalInformationDetail</Role>
      <ShortName>NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSTables</ParentRole>
      <Position>83</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>042150 - Disclosure - NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Changes in Servicing Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSChangesInServicingAssetsDetail</Role>
      <ShortName>NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Changes in Servicing Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSTables</ParentRole>
      <Position>84</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>042250 - Disclosure - NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Changes in Impairment Allowance (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSChangesInImpairmentAllowanceDetail</Role>
      <ShortName>NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Changes in Impairment Allowance (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSTables</ParentRole>
      <Position>85</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>042300 - Disclosure - NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Components of Net Servicing Income (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSComponentsOfNetServicingIncomeDetail</Role>
      <ShortName>NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Components of Net Servicing Income (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSTables</ParentRole>
      <Position>86</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>042350 - Disclosure - NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Key Economic Assumptions Used in Determining Fair Value at Time of Sale of Loans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSKeyEconomicAssumptionsUsedInDeterminingFairValueAtTimeOfSaleOfLoansDetail</Role>
      <ShortName>NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Key Economic Assumptions Used in Determining Fair Value at Time of Sale of Loans (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSTables</ParentRole>
      <Position>87</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>042400 - Disclosure - NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Weighted-Averages of Key Economic Assumptions in Valuation Model (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSWeightedAveragesOfKeyEconomicAssumptionsInValuationModelDetail</Role>
      <ShortName>NON-CONSOLIDATED VARIABLE INTEREST ENTITIES (VIEs) AND SERVICING ASSETS - Weighted-Averages of Key Economic Assumptions in Valuation Model (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/NONCONSOLIDATEDVARIABLEINTERESTENTITIESVIEsANDSERVICINGASSETSTables</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>042420 - Disclosure - DEPOSITS - Narratives (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEPOSITSNarrativesDetail</Role>
      <ShortName>DEPOSITS - Narratives (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>042425 - Disclosure - DEPOSITS - Summary of Deposit Balances (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEPOSITSSummaryOfDepositBalancesDetail</Role>
      <ShortName>DEPOSITS - Summary of Deposit Balances (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>90</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>042427 - Disclosure - DEPOSITS - Certificates of Deposits Mature (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEPOSITSCertificatesOfDepositsMatureDetail</Role>
      <ShortName>DEPOSITS - Certificates of Deposits Mature (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>042525 - Disclosure - DEPOSITS - Interest Expenses on deposits (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DEPOSITSInterestExpensesOnDepositsDetail</Role>
      <ShortName>DEPOSITS - Interest Expenses on deposits (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>92</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>042575 - Disclosure - SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) - Narratives (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSNarrativesDetail</Role>
      <ShortName>SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) - Narratives (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSTables</ParentRole>
      <Position>93</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>042600 - Disclosure - SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) - Securities Sold Under Agreements to Repurchase (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSSecuritiesSoldUnderAgreementsToRepurchaseDetail</Role>
      <ShortName>SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) - Securities Sold Under Agreements to Repurchase (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSTables</ParentRole>
      <Position>94</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>042650 - Disclosure - SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) - Securities Sold Under Agreements to Repurchase (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSSecuritiesSoldUnderAgreementsToRepurchaseParentheticalDetail</Role>
      <ShortName>SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) - Securities Sold Under Agreements to Repurchase (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSTables</ParentRole>
      <Position>95</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>042700 - Disclosure - SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) - Schedule of Repurchase Agreement Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSScheduleOfRepurchaseAgreementMaturityDetail</Role>
      <ShortName>SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) - Schedule of Repurchase Agreement Maturity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSTables</ParentRole>
      <Position>96</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>042750 - Disclosure - SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) - Repurchase Agreements Grouped by Counterparty (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSRepurchaseAgreementsGroupedByCounterpartyDetail</Role>
      <ShortName>SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE (REPURCHASE AGREEMENTS) - Repurchase Agreements Grouped by Counterparty (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/SECURITIESSOLDUNDERAGREEMENTSTOREPURCHASEREPURCHASEAGREEMENTSTables</ParentRole>
      <Position>97</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>042800 - Disclosure - ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB) - Summary of Advances from FHLB (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureADVANCESFROMTHEFEDERALHOMELOANBANKFHLBSummaryOfAdvancesFromFHLBDetail</Role>
      <ShortName>ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB) - Summary of Advances from FHLB (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/ADVANCESFROMTHEFEDERALHOMELOANBANKFHLBTables</ParentRole>
      <Position>98</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>042850 - Disclosure - ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB) - Summary of Advances from FHLB (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureADVANCESFROMTHEFEDERALHOMELOANBANKFHLBSummaryOfAdvancesFromFHLBParentheticalDetail</Role>
      <ShortName>ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB) - Summary of Advances from FHLB (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/ADVANCESFROMTHEFEDERALHOMELOANBANKFHLBTables</ParentRole>
      <Position>99</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>042900 - Disclosure - ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB) - Advances from FHLB Mature (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureADVANCESFROMTHEFEDERALHOMELOANBANKFHLBAdvancesFromFHLBMatureDetail</Role>
      <ShortName>ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB) - Advances from FHLB Mature (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/ADVANCESFROMTHEFEDERALHOMELOANBANKFHLBTables</ParentRole>
      <Position>100</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>042950 - Disclosure - ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB) - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureADVANCESFROMTHEFEDERALHOMELOANBANKFHLBAdditionalInformationDetail</Role>
      <ShortName>ADVANCES FROM THE FEDERAL HOME LOAN BANK (FHLB) - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/ADVANCESFROMTHEFEDERALHOMELOANBANKFHLBTables</ParentRole>
      <Position>101</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>043500 - Disclosure - OTHER LONG-TERM BORROWINGS - Components of Other Borrowings (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/OTHERLONGTERMBORROWINGSComponentsOfOtherBorrowingsDetail</Role>
      <ShortName>OTHER LONG-TERM BORROWINGS - Components of Other Borrowings (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>102</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>043550 - Disclosure - OTHER LONG-TERM BORROWINGS - Components of Other Borrowings (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/OTHERLONGTERMBORROWINGSComponentsOfOtherBorrowingsParentheticalDetail</Role>
      <ShortName>OTHER LONG-TERM BORROWINGS - Components of Other Borrowings (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>103</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>043700 - Disclosure - EARNINGS PER COMMON SHARE - Calculations of Earnings Per Common Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/EARNINGSPERCOMMONSHARECalculationsOfEarningsPerCommonShareDetail</Role>
      <ShortName>EARNINGS PER COMMON SHARE - Calculations of Earnings Per Common Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>104</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>043705 - Disclosure - EARNINGS PER COMMON SHARE - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/EARNINGSPERCOMMONSHAREAdditionalInformationDetail</Role>
      <ShortName>EARNINGS PER COMMON SHARE - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>105</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>043710 - Disclosure - STOCK-BASED COMPENSATION - Omnibus Plan - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATIONOmnibusPlanAdditionalInformationDetail</Role>
      <ShortName>STOCK-BASED COMPENSATION - Omnibus Plan - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>106</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R107.htm</HtmlFileName>
      <LongName>043711 - Disclosure - STOCK-BASED COMPENSATION - Restricted Stock - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATIONRestrictedStockAdditionalInformationDetail</Role>
      <ShortName>STOCK-BASED COMPENSATION - Restricted Stock - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>107</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R108.htm</HtmlFileName>
      <LongName>043712 - Disclosure - STOCK-BASED COMPENSATION - Restricted Stock Activity Under Omnibus Plan (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATIONRestrictedStockActivityUnderOmnibusPlanDetail</Role>
      <ShortName>STOCK-BASED COMPENSATION - Restricted Stock Activity Under Omnibus Plan (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>108</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R109.htm</HtmlFileName>
      <LongName>043713 - Disclosure - STOCK-BASED COMPENSATION - Restricted Stock Activity Under Omnibus Plan (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATIONRestrictedStockActivityUnderOmnibusPlanParentheticalDetail</Role>
      <ShortName>STOCK-BASED COMPENSATION - Restricted Stock Activity Under Omnibus Plan (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>109</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R110.htm</HtmlFileName>
      <LongName>043714 - Disclosure - STOCK-BASED COMPENSATION - Performance Units - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATIONPerformanceUnitsAdditionalInformationDetail</Role>
      <ShortName>STOCK-BASED COMPENSATION - Performance Units - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>110</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R111.htm</HtmlFileName>
      <LongName>043715 - Disclosure - STOCK-BASED COMPENSATION - Performance Units - Performance Unit Activity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATIONPerformanceUnitsPerformanceUnitActivityDetail</Role>
      <ShortName>STOCK-BASED COMPENSATION - Performance Units - Performance Unit Activity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>111</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R112.htm</HtmlFileName>
      <LongName>043717 - Disclosure - STOCK-BASED COMPENSATION - Summary of Valuation Assumptions (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATIONSummaryOfValuationAssumptionsDetail</Role>
      <ShortName>STOCK-BASED COMPENSATION - Summary of Valuation Assumptions (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>112</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R113.htm</HtmlFileName>
      <LongName>043718 - Disclosure - STOCK-BASED COMPENSATION - Treasury Stock - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKBASEDCOMPENSATIONTreasuryStockAdditionalInformationDetail</Role>
      <ShortName>STOCK-BASED COMPENSATION - Treasury Stock - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>113</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R114.htm</HtmlFileName>
      <LongName>043750 - Disclosure - STOCKHOLDERS' EQUITY - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureSTOCKHOLDERSEQUITYAdditionalInformationDetail</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>114</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R115.htm</HtmlFileName>
      <LongName>043760 - Disclosure - STOCKHOLDERS' EQUITY - Common Stock (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKHOLDERSEQUITYCommonStockDetail</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Common Stock (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>115</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R116.htm</HtmlFileName>
      <LongName>043761 - Disclosure - STOCKHOLDERS' EQUITY - Common Stock (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKHOLDERSEQUITYCommonStockParentheticalDetail</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Common Stock (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>116</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R117.htm</HtmlFileName>
      <LongName>043765 - Disclosure - STOCKHOLDERS' EQUITY - Treasury Shares (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/STOCKHOLDERSEQUITYTreasurySharesDetail</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Treasury Shares (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>117</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R118.htm</HtmlFileName>
      <LongName>043770 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS - Change in Accumulated Other Comprehensive Loss by Component (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSSChangeInAccumulatedOtherComprehensiveLossByComponentDetail</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE LOSS - Change in Accumulated Other Comprehensive Loss by Component (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>118</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R119.htm</HtmlFileName>
      <LongName>043820 - Disclosure - EMPLOYEE BENEFIT PLANS - Components of Net Periodic Benefit (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/EMPLOYEEBENEFITPLANSComponentsOfNetPeriodicBenefitDetail</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS - Components of Net Periodic Benefit (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>119</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R120.htm</HtmlFileName>
      <LongName>044000 - Disclosure - INCOME TAXES - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureINCOMETAXESAdditionalInformationDetail</Role>
      <ShortName>INCOME TAXES - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>120</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R121.htm</HtmlFileName>
      <LongName>044150 - Disclosure - INCOME TAXES- Significant components of deferred tax assets and liabilities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/INCOMETAXESSignificantComponentsOfDeferredTaxAssetsAndLiabilitiesDetail</Role>
      <ShortName>INCOME TAXES- Significant components of deferred tax assets and liabilities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>121</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R122.htm</HtmlFileName>
      <LongName>044250 - Disclosure - FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureFAIRVALUEAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetail</Role>
      <ShortName>FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>122</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R123.htm</HtmlFileName>
      <LongName>044400 - Disclosure - FAIR VALUE - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureFAIRVALUEFairValueOfAssetsAndLiabilitiesMeasuredOnRecurringBasisDetail</Role>
      <ShortName>FAIR VALUE - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>123</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R124.htm</HtmlFileName>
      <LongName>044401 - Disclosure - FAIR VALUE - Fair Value of Assets and Liabilities Measured on Recurring Basis (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/FAIRVALUEFairValueOfAssetsAndLiabilitiesMeasuredOnRecurringBasisParentheticalDetail</Role>
      <ShortName>FAIR VALUE - Fair Value of Assets and Liabilities Measured on Recurring Basis (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>124</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R125.htm</HtmlFileName>
      <LongName>044450 - Disclosure - FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureFAIRVALUEAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisUsingSignificantUnobservableInputsLevel3Detail</Role>
      <ShortName>FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>125</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R126.htm</HtmlFileName>
      <LongName>044500 - Disclosure - FAIR VALUE - Impairment of Valuation Adjustments were Recorded for Assets Recognized at Fair Value (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureFAIRVALUEImpairmentOfValuationAdjustmentsWereRecordedForAssetsRecognizedAtFairValueDetail</Role>
      <ShortName>FAIR VALUE - Impairment of Valuation Adjustments were Recorded for Assets Recognized at Fair Value (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>126</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R127.htm</HtmlFileName>
      <LongName>044650 - Disclosure - FAIR VALUE - Fair Value (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureFAIRVALUEFairValueDetail</Role>
      <ShortName>FAIR VALUE - Fair Value (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>127</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R128.htm</HtmlFileName>
      <LongName>044660 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Disaggregation of Revenue (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSDisaggregationOfRevenueDetail</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS - Disaggregation of Revenue (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>128</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R129.htm</HtmlFileName>
      <LongName>044671 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Activity of Contract Liability (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSActivityOfContractLiabilityDetail</Role>
      <ShortName>REVENUE FROM CONTRACTS WITH CUSTOMERS - Activity of Contract Liability (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>129</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R130.htm</HtmlFileName>
      <LongName>044680 - Disclosure - SEGMENT INFORMATION - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SEGMENTINFORMATIONAdditionalInformationDetail</Role>
      <ShortName>SEGMENT INFORMATION - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>130</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R131.htm</HtmlFileName>
      <LongName>044681 - Disclosure - SEGMENT INFORMATION - Information about Reportable Segments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SEGMENTINFORMATIONInformationAboutReportableSegmentsDetail</Role>
      <ShortName>SEGMENT INFORMATION - Information about Reportable Segments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>131</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R132.htm</HtmlFileName>
      <LongName>044682 - Disclosure - SEGMENT INFORMATION - Reconciliation of Reportable Segment Financial Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SEGMENTINFORMATIONReconciliationOfReportableSegmentFinancialInformationDetail</Role>
      <ShortName>SEGMENT INFORMATION - Reconciliation of Reportable Segment Financial Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>132</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R133.htm</HtmlFileName>
      <LongName>044750 - Disclosure - SUPPLEMENTAL STATEMENT OF CASH FLOW INFORMATION - Supplemental Cash Flow Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/SUPPLEMENTALSTATEMENTOFCASHFLOWINFORMATIONSupplementalCashFlowInformationDetail</Role>
      <ShortName>SUPPLEMENTAL STATEMENT OF CASH FLOW INFORMATION - Supplemental Cash Flow Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>133</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R134.htm</HtmlFileName>
      <LongName>045000 - Disclosure - REGULATORY MATTERS, COMMITMENTS, AND CONTINGENCIES - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/REGULATORYMATTERSCOMMITMENTSANDCONTINGENCIESAdditionalInformationDetail</Role>
      <ShortName>REGULATORY MATTERS, COMMITMENTS, AND CONTINGENCIES - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>134</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R135.htm</HtmlFileName>
      <LongName>045001 - Disclosure - REGULATORY MATTERS, COMMITMENTS, AND CONTINGENCIES - Regulatory capital positions (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/REGULATORYMATTERSCOMMITMENTSANDCONTINGENCIESRegulatoryCapitalPositionsDetail</Role>
      <ShortName>REGULATORY MATTERS, COMMITMENTS, AND CONTINGENCIES - Regulatory capital positions (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>135</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R136.htm</HtmlFileName>
      <LongName>045300 - Disclosure - FIRST BANCORP. (Holding Company Only) Financial Information - Statements of Financial Condition (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/DisclosureFIRSTBANCORPHoldingCompanyOnlyFinancialInformationStatementsOfFinancialConditionDetail</Role>
      <ShortName>FIRST BANCORP. (Holding Company Only) Financial Information - Statements of Financial Condition (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/FIRSTBANCORPHoldingCompanyOnlyFinancialInformationTables</ParentRole>
      <Position>136</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R137.htm</HtmlFileName>
      <LongName>045350 - Disclosure - FIRST BANCORP. (Holding Company Only) Financial Information - Statements of Income (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/FIRSTBANCORPHoldingCompanyOnlyFinancialInformationStatementsOfIncomeDetail</Role>
      <ShortName>FIRST BANCORP. (Holding Company Only) Financial Information - Statements of Income (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.firstbankpr.com/role/FIRSTBANCORPHoldingCompanyOnlyFinancialInformationTables</ParentRole>
      <Position>137</Position>
    </Report>
    <Report instance="fbp20230630Q2.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R138.htm</HtmlFileName>
      <LongName>045360 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.firstbankpr.com/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Uncategorized</MenuCategory>
      <Position>138</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 15 fact(s) appearing in ix:hidden were eligible for transformation: dei:DocumentTransitionReport, dei:EntityEmergingGrowthCompany, dei:EntityFilerCategory, dei:EntityShellCompany, dei:EntitySmallBusiness, dei:SecurityExchangeName, us-gaap:AociTaxAttributableToParent, us-gaap:AssetsFairValueAdjustment, us-gaap:CommonStockParOrStatedValuePerShare, us-gaap:CommonStockSharesAuthorized, us-gaap:CommonStockSharesIssued, us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1, us-gaap:StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithRegulatoryApproval -  fbp20230630Q2.htm 13, 14, 15, 16, 17, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30</Log>
    <Log type="Warning">[dq-0712-Presentation-Base-Set-Order] Role '045350 - Disclosure - FIRST BANCORP. (Holding Company Only) Financial Information - Statements of Income (Detail)', a level 4, Detail role, appears before '045360 - Disclosure - Insider Trading Arrangements', a level 1, Note role. fbp-20230630.xsd 545, 887</Log>
  </Logs>
  <InputFiles>
    <File doctype="10-Q" original="fbp20230630Q2.htm">fbp20230630Q2.htm</File>
    <File>exhibit311.htm</File>
    <File>exhibit312.htm</File>
    <File>exhibit321.htm</File>
    <File>exhibit322.htm</File>
    <File>fbp-20230630.xsd</File>
    <File>fbp-20230630_cal.xml</File>
    <File>fbp-20230630_def.xml</File>
    <File>fbp-20230630_lab.xml</File>
    <File>fbp-20230630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="2">http://fasb.org/srt/2023</BaseTaxonomy>
    <BaseTaxonomy items="4669">http://fasb.org/us-gaap/2023</BaseTaxonomy>
    <BaseTaxonomy items="30">http://xbrl.sec.gov/dei/2023</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2023</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
