<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>1258</ContextCount>
  <ElementCount>497</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>142</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>10</UnitCount>
  <MyReports>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - COVER PAGE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/COVERPAGE</Role>
      <ShortName>COVER PAGE</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>9952151 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>9952152 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>9952153 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFINCOME</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>9952154 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952155 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITY</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952156 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>9952157 - Disclosure - ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/ORGANIZATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES</Role>
      <ShortName>ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952158 - Disclosure - DEBT SECURITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEBTSECURITIES</Role>
      <ShortName>DEBT SECURITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952159 - Disclosure - LOANS AND THE ALLOWANCE FOR CREDIT LOSSES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSES</Role>
      <ShortName>LOANS AND THE ALLOWANCE FOR CREDIT LOSSES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - GOODWILL</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/GOODWILL</Role>
      <ShortName>GOODWILL</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - LEASES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LEASES</Role>
      <ShortName>LEASES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - DEPOSITS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEPOSITS</Role>
      <ShortName>DEPOSITS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - BORROWINGS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/BORROWINGS</Role>
      <ShortName>BORROWINGS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - COMMITMENTS AND CONTINGENCIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/COMMITMENTSANDCONTINGENCIES</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SHAREHOLDERSEQUITY</Role>
      <ShortName>SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>9952166 - Disclosure - EARNINGS PER COMMON SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/EARNINGSPERCOMMONSHARE</Role>
      <ShortName>EARNINGS PER COMMON SHARE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>9952167 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/INCOMETAXES</Role>
      <ShortName>INCOME TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9952168 - Disclosure - FAIR VALUE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/FAIRVALUE</Role>
      <ShortName>FAIR VALUE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>9952169 - Disclosure - DERIVATIVES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DERIVATIVES</Role>
      <ShortName>DERIVATIVES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>9952170 - Disclosure - SEGMENT REPORTING</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SEGMENTREPORTING</Role>
      <ShortName>SEGMENT REPORTING</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>9952171 - Disclosure - TAX CREDIT INVESTMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/TAXCREDITINVESTMENTS</Role>
      <ShortName>TAX CREDIT INVESTMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9952172 - Disclosure - REGULATORY CAPITAL MATTERS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/REGULATORYCAPITALMATTERS</Role>
      <ShortName>REGULATORY CAPITAL MATTERS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9955511 - Disclosure - ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/ORGANIZATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies</Role>
      <ShortName>ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9955512 - Disclosure - DEBT SECURITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEBTSECURITIESTables</Role>
      <ShortName>DEBT SECURITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/DEBTSECURITIES</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9955513 - Disclosure - LOANS AND THE ALLOWANCE FOR CREDIT LOSSES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSESTables</Role>
      <ShortName>LOANS AND THE ALLOWANCE FOR CREDIT LOSSES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSES</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>9955514 - Disclosure - LEASES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LEASESTables</Role>
      <ShortName>LEASES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/LEASES</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>9955515 - Disclosure - DEPOSITS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEPOSITSTables</Role>
      <ShortName>DEPOSITS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/DEPOSITS</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9955516 - Disclosure - BORROWINGS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/BORROWINGSTables</Role>
      <ShortName>BORROWINGS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/BORROWINGS</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9955517 - Disclosure - COMMITMENTS AND CONTINGENCIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/COMMITMENTSANDCONTINGENCIESTables</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/COMMITMENTSANDCONTINGENCIES</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9955518 - Disclosure - SHAREHOLDERS' EQUITY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SHAREHOLDERSEQUITYTables</Role>
      <ShortName>SHAREHOLDERS' EQUITY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/SHAREHOLDERSEQUITY</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9955519 - Disclosure - EARNINGS PER COMMON SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/EARNINGSPERCOMMONSHARETables</Role>
      <ShortName>EARNINGS PER COMMON SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/EARNINGSPERCOMMONSHARE</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9955520 - Disclosure - FAIR VALUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/FAIRVALUETables</Role>
      <ShortName>FAIR VALUE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/FAIRVALUE</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9955521 - Disclosure - DERIVATIVES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DERIVATIVESTables</Role>
      <ShortName>DERIVATIVES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/DERIVATIVES</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9955522 - Disclosure - SEGMENT REPORTING (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SEGMENTREPORTINGTables</Role>
      <ShortName>SEGMENT REPORTING (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/SEGMENTREPORTING</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9955523 - Disclosure - REGULATORY CAPITAL MATTERS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/REGULATORYCAPITALMATTERSTables</Role>
      <ShortName>REGULATORY CAPITAL MATTERS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://myfw.com/role/REGULATORYCAPITALMATTERS</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9955524 - Disclosure - ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration of Credit Risk (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/ORGANIZATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESConcentrationofCreditRiskDetails</Role>
      <ShortName>ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration of Credit Risk (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9955525 - Disclosure - DEBT SECURITIES - Amortized cost and fair value of securities available-for-sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEBTSECURITIESAmortizedcostandfairvalueofsecuritiesavailableforsaleDetails</Role>
      <ShortName>DEBT SECURITIES - Amortized cost and fair value of securities available-for-sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9955526 - Disclosure - DEBT SECURITIES - Amortized cost and fair value of securities held-to-maturity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEBTSECURITIESAmortizedcostandfairvalueofsecuritiesheldtomaturityDetails</Role>
      <ShortName>DEBT SECURITIES - Amortized cost and fair value of securities held-to-maturity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9955527 - Disclosure - DEBT SECURITIES - Amortized cost and estimated fair value of held-to-maturity and available-for-sale securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEBTSECURITIESAmortizedcostandestimatedfairvalueofheldtomaturityandavailableforsalesecuritiesDetails</Role>
      <ShortName>DEBT SECURITIES - Amortized cost and estimated fair value of held-to-maturity and available-for-sale securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9955528 - Disclosure - DEBT SECURITIES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEBTSECURITIESNarrativeDetails</Role>
      <ShortName>DEBT SECURITIES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9955529 - Disclosure - DEBT SECURITIES - AFS debt securities that were in an unrealized loss position (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEBTSECURITIESAFSdebtsecuritiesthatwereinanunrealizedlosspositionDetails</Role>
      <ShortName>DEBT SECURITIES - AFS debt securities that were in an unrealized loss position (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9955530 - Disclosure - DEBT SECURITIES - Allowance for credit losses to HTM securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEBTSECURITIESAllowanceforcreditlossestoHTMsecuritiesDetails</Role>
      <ShortName>DEBT SECURITIES - Allowance for credit losses to HTM securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9955531 - Disclosure - LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Summary of loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSESSummaryofloansDetails</Role>
      <ShortName>LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Summary of loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9955532 - Disclosure - LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSESNarrativeDetails</Role>
      <ShortName>LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9955533 - Disclosure - LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Aging analysis of recorded investments by class (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSESAginganalysisofrecordedinvestmentsbyclassDetails</Role>
      <ShortName>LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Aging analysis of recorded investments by class (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9955534 - Disclosure - LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Loan modification (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSESLoanmodificationDetails</Role>
      <ShortName>LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Loan modification (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9955535 - Disclosure - LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Recorded investment in non-accrual loans by class (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSESRecordedinvestmentinnonaccrualloansbyclassDetails</Role>
      <ShortName>LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Recorded investment in non-accrual loans by class (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9955536 - Disclosure - LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Summary of nonaccrual loans with collateral (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSESSummaryofnonaccrualloanswithcollateralDetails</Role>
      <ShortName>LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Summary of nonaccrual loans with collateral (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9955537 - Disclosure - LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Allowance for loan losses by portfolio (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSESAllowanceforloanlossesbyportfolioDetails</Role>
      <ShortName>LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Allowance for loan losses by portfolio (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9955538 - Disclosure - LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Recorded investment in company's loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LOANSANDTHEALLOWANCEFORCREDITLOSSESRecordedinvestmentincompanysloansDetails</Role>
      <ShortName>LOANS AND THE ALLOWANCE FOR CREDIT LOSSES - Recorded investment in company's loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9955539 - Disclosure - GOODWILL - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/GOODWILLNarrativeDetails</Role>
      <ShortName>GOODWILL - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9955540 - Disclosure - LEASES - Leases balance sheet location (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LEASESLeasesbalancesheetlocationDetails</Role>
      <ShortName>LEASES - Leases balance sheet location (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9955541 - Disclosure - LEASES - Leases costs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LEASESLeasescostsDetails</Role>
      <ShortName>LEASES - Leases costs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9955542 - Disclosure - LEASES - Lease maturity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LEASESLeasematurityDetails</Role>
      <ShortName>LEASES - Lease maturity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9955543 - Disclosure - LEASES - Expected amortization expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/LEASESExpectedamortizationexpenseDetails</Role>
      <ShortName>LEASES - Expected amortization expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9955544 - Disclosure - DEPOSITS - Schedule of interest-bearing deposits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEPOSITSScheduleofinterestbearingdepositsDetails</Role>
      <ShortName>DEPOSITS - Schedule of interest-bearing deposits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9955545 - Disclosure - DEPOSITS - Schedule of time deposits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DEPOSITSScheduleoftimedepositsDetails</Role>
      <ShortName>DEPOSITS - Schedule of time deposits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9955546 - Disclosure - BORROWINGS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/BORROWINGSNarrativeDetails</Role>
      <ShortName>BORROWINGS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9955547 - Disclosure - BORROWINGS - Schedule of borrowings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/BORROWINGSScheduleofborrowingsDetails</Role>
      <ShortName>BORROWINGS - Schedule of borrowings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9955548 - Disclosure - BORROWINGS - Schedule of subordinated debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/BORROWINGSScheduleofsubordinateddebtDetails</Role>
      <ShortName>BORROWINGS - Schedule of subordinated debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9955549 - Disclosure - COMMITMENTS AND CONTINGENCIES - Schedule of financial instruments with credit risk (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/COMMITMENTSANDCONTINGENCIESScheduleoffinancialinstrumentswithcreditriskDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - Schedule of financial instruments with credit risk (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9955550 - Disclosure - COMMITMENTS AND CONTINGENCIES - Schedule of unfunded loan commitments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/COMMITMENTSANDCONTINGENCIESScheduleofunfundedloancommitmentsDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - Schedule of unfunded loan commitments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9955551 - Disclosure - SHAREHOLDERS' EQUITY - Common stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SHAREHOLDERSEQUITYCommonstockDetails</Role>
      <ShortName>SHAREHOLDERS' EQUITY - Common stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9955552 - Disclosure - SHAREHOLDERS' EQUITY - Stock based compensation plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SHAREHOLDERSEQUITYStockbasedcompensationplansDetails</Role>
      <ShortName>SHAREHOLDERS' EQUITY - Stock based compensation plans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9955553 - Disclosure - SHAREHOLDERS' EQUITY - Stock options activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SHAREHOLDERSEQUITYStockoptionsactivityDetails</Role>
      <ShortName>SHAREHOLDERS' EQUITY - Stock options activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9955554 - Disclosure - SHAREHOLDERS' EQUITY - Share awards (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SHAREHOLDERSEQUITYShareawardsDetails</Role>
      <ShortName>SHAREHOLDERS' EQUITY - Share awards (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9955555 - Disclosure - SHAREHOLDERS' EQUITY - Time vesting units (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SHAREHOLDERSEQUITYTimevestingunitsDetails</Role>
      <ShortName>SHAREHOLDERS' EQUITY - Time vesting units (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9955556 - Disclosure - SHAREHOLDERS' EQUITY - Financial performance units (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SHAREHOLDERSEQUITYFinancialperformanceunitsDetails</Role>
      <ShortName>SHAREHOLDERS' EQUITY - Financial performance units (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9955557 - Disclosure - EARNINGS PER COMMON SHARE - Computation of earnings per share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/EARNINGSPERCOMMONSHAREComputationofearningspershareDetails</Role>
      <ShortName>EARNINGS PER COMMON SHARE - Computation of earnings per share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9955558 - Disclosure - EARNINGS PER COMMON SHARE - Schedule of potentially dilutive Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/EARNINGSPERCOMMONSHAREScheduleofpotentiallydilutiveSecuritiesDetails</Role>
      <ShortName>EARNINGS PER COMMON SHARE - Schedule of potentially dilutive Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9955559 - Disclosure - INCOME TAXES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/INCOMETAXESDetails</Role>
      <ShortName>INCOME TAXES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://myfw.com/role/INCOMETAXES</ParentRole>
      <Position>73</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>9955560 - Disclosure - FAIR VALUE - Summary of assets measured at fair value on recurring basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/FAIRVALUESummaryofassetsmeasuredatfairvalueonrecurringbasisDetails</Role>
      <ShortName>FAIR VALUE - Summary of assets measured at fair value on recurring basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>9955561 - Disclosure - FAIR VALUE - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/FAIRVALUENarrativeDetails</Role>
      <ShortName>FAIR VALUE - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>9955562 - Disclosure - FAIR VALUE - Summary of information about the fair value carrying amount and unpaid principal outstanding of loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/FAIRVALUESummaryofinformationaboutthefairvaluecarryingamountandunpaidprincipaloutstandingofloansDetails</Role>
      <ShortName>FAIR VALUE - Summary of information about the fair value carrying amount and unpaid principal outstanding of loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>9955563 - Disclosure - FAIR VALUE - Summary of changes in fair value of loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/FAIRVALUESummaryofchangesinfairvalueofloansDetails</Role>
      <ShortName>FAIR VALUE - Summary of changes in fair value of loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>9955564 - Disclosure - FAIR VALUE - Summary of assets measured at level 3 fair value on recurring basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/FAIRVALUESummaryofassetsmeasuredatlevel3fairvalueonrecurringbasisDetails</Role>
      <ShortName>FAIR VALUE - Summary of assets measured at level 3 fair value on recurring basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>9955565 - Disclosure - FAIR VALUE - Summary of assets and liabilities measured at fair value on a recurring or nonrecurring, the significant unobservable inputs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/FAIRVALUESummaryofassetsandliabilitiesmeasuredatfairvalueonarecurringornonrecurringthesignificantunobservableinputsDetails</Role>
      <ShortName>FAIR VALUE - Summary of assets and liabilities measured at fair value on a recurring or nonrecurring, the significant unobservable inputs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>9955566 - Disclosure - FAIR VALUE - Summary of carrying amounts and estimated fair values for financial instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/FAIRVALUESummaryofcarryingamountsandestimatedfairvaluesforfinancialinstrumentsDetails</Role>
      <ShortName>FAIR VALUE - Summary of carrying amounts and estimated fair values for financial instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>9955567 - Disclosure - DERIVATIVES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DERIVATIVESNarrativeDetails</Role>
      <ShortName>DERIVATIVES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>9955568 - Disclosure - DERIVATIVES - Schedule of Derivatives by Balance Sheet Location (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DERIVATIVESScheduleofDerivativesbyBalanceSheetLocationDetails</Role>
      <ShortName>DERIVATIVES - Schedule of Derivatives by Balance Sheet Location (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>9955569 - Disclosure - DERIVATIVES - Derivative Reclassified into Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DERIVATIVESDerivativeReclassifiedintoIncomeDetails</Role>
      <ShortName>DERIVATIVES - Derivative Reclassified into Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>9955570 - Disclosure - DERIVATIVES - Cumulative basis adjustments for fair value hedges (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DERIVATIVESCumulativebasisadjustmentsforfairvaluehedgesDetails</Role>
      <ShortName>DERIVATIVES - Cumulative basis adjustments for fair value hedges (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>9955571 - Disclosure - DERIVATIVES - Effects of the fair value hedge relationships on the Condensed Consolidated Statements of Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/DERIVATIVESEffectsofthefairvaluehedgerelationshipsontheCondensedConsolidatedStatementsofIncomeDetails</Role>
      <ShortName>DERIVATIVES - Effects of the fair value hedge relationships on the Condensed Consolidated Statements of Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>9955572 - Disclosure - SEGMENT REPORTING (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/SEGMENTREPORTINGDetails</Role>
      <ShortName>SEGMENT REPORTING (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://myfw.com/role/SEGMENTREPORTINGTables</ParentRole>
      <Position>86</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>9955573 - Disclosure - TAX CREDIT INVESTMENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/TAXCREDITINVESTMENTSDetails</Role>
      <ShortName>TAX CREDIT INVESTMENTS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://myfw.com/role/TAXCREDITINVESTMENTS</ParentRole>
      <Position>87</Position>
    </Report>
    <Report instance="myfw-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>9955574 - Disclosure - REGULATORY CAPITAL MATTERS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://myfw.com/role/REGULATORYCAPITALMATTERSDetails</Role>
      <ShortName>REGULATORY CAPITAL MATTERS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://myfw.com/role/REGULATORYCAPITALMATTERSTables</ParentRole>
      <Position>88</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="myfw-20260331.htm">myfw-20260331.htm</File>
    <File>myfw-20260331.xsd</File>
    <File>myfw-20260331_cal.xml</File>
    <File>myfw-20260331_def.xml</File>
    <File>myfw-20260331_lab.xml</File>
    <File>myfw-20260331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="1">http://fasb.org/srt/2025</BaseTaxonomy>
    <BaseTaxonomy items="2164">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="30">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
