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  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2026"
  xmlns:ffd="http://xbrl.sec.gov/ffd/2026"
  xmlns:iso4217="http://www.xbrl.org/2003/iso4217"
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      xlink:href="https://xbrl.sec.gov/ffd/2026/ffd-2026.xsd"
      xlink:type="simple"/>
    <context id="rc">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000036377</identifier>
        </entity>
        <period>
            <startDate>2026-08-31</startDate>
            <endDate>2026-08-31</endDate>
        </period>
    </context>
    <context id="offrl_1">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000036377</identifier>
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                <xbrldi:typedMember dimension="ffd:OfferingAxis">
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        <period>
            <startDate>2026-08-31</startDate>
            <endDate>2026-08-31</endDate>
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    </context>
    <unit id="USD">
        <measure>iso4217:USD</measure>
    </unit>
    <unit id="pure">
        <measure>pure</measure>
    </unit>
    <unit id="Shares">
        <measure>shares</measure>
    </unit>
    <ffd:FormTp contextRef="rc" id="ixv-330">S-4</ffd:FormTp>
    <ffd:SubmissnTp contextRef="rc" id="ixv-331">S-4</ffd:SubmissnTp>
    <ffd:FeeExhibitTp contextRef="rc" id="ixv-332">EX-FILING FEES</ffd:FeeExhibitTp>
    <dei:EntityCentralIndexKey contextRef="rc" id="ixv-333">0000036377</dei:EntityCentralIndexKey>
    <dei:EntityRegistrantName contextRef="rc" id="ixv-334">FIRST HAWAIIAN, INC.</dei:EntityRegistrantName>
    <ffd:OfferingTableNa contextRef="rc" id="hiddenrcOfferingTableNa" xsi:nil="true"/>
    <ffd:OffsetTableNa contextRef="rc" id="hiddenrcOffsetTableNa">N/A</ffd:OffsetTableNa>
    <ffd:CombinedProspectusTableNa contextRef="rc" id="hiddenrcCombinedProspectusTableNa">N/A</ffd:CombinedProspectusTableNa>
    <ffd:FormTp contextRef="rc" id="ixv-362">S-4</ffd:FormTp>
    <dei:EntityRegistrantName contextRef="rc" id="ixv-363">FIRST HAWAIIAN, INC.</dei:EntityRegistrantName>
    <ffd:PrevslyPdFlg contextRef="offrl_1" id="ixv-364">false</ffd:PrevslyPdFlg>
    <ffd:OfferingSctyTp contextRef="offrl_1" id="ixv-365">Equity</ffd:OfferingSctyTp>
    <ffd:OfferingSctyTitl contextRef="offrl_1" id="ixv-366">Common stock, par value $0.01 per share</ffd:OfferingSctyTitl>
    <ffd:FeesOthrRuleFlg contextRef="offrl_1" id="ixv-367">true</ffd:FeesOthrRuleFlg>
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      contextRef="offrl_1"
      decimals="0"
      id="ixv-368"
      unitRef="Shares">68611250</ffd:AmtSctiesRegd>
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      contextRef="offrl_1"
      decimals="2"
      id="ixv-369"
      unitRef="USD">1756464375.00</ffd:MaxAggtOfferingPric>
    <ffd:FeeRate
      contextRef="offrl_1"
      decimals="7"
      id="ixv-370"
      unitRef="pure">0.0001381</ffd:FeeRate>
    <ffd:FeeAmt
      contextRef="offrl_1"
      decimals="2"
      id="ixv-371"
      unitRef="USD">242567.73</ffd:FeeAmt>
    <ffd:TtlOfferingAmt contextRef="rc" decimals="2" id="ixv-372" unitRef="USD">1756464375.00</ffd:TtlOfferingAmt>
    <ffd:TtlFeeAmt contextRef="rc" decimals="2" id="ixv-373" unitRef="USD">242567.73</ffd:TtlFeeAmt>
    <ffd:TtlPrevslyPdAmt contextRef="rc" decimals="2" id="ixv-374" unitRef="USD">0.00</ffd:TtlPrevslyPdAmt>
    <ffd:TtlOffsetAmt contextRef="rc" decimals="2" id="ixv-375" unitRef="USD">0.00</ffd:TtlOffsetAmt>
    <ffd:NetFeeAmt contextRef="rc" decimals="2" id="ixv-376" unitRef="USD">242567.73</ffd:NetFeeAmt>
    <ffd:OfferingNote contextRef="offrl_1" id="ixv-377">The number of shares of common stock, par value $0.01 per share, of First Hawaiian, Inc. ("FHI" and, such shares, the "FHI common stock") being registered is based upon (i) an estimate of the maximum number of shares of common stock, no par value, of TriCo Bancshares ("TriCo" and, such shares, the "TriCo common stock") outstanding or issuable or expected to be exchanged in connection with the merger of Horizon Merger Sub, Inc. ("Merger Sub"), a wholly owned subsidiary of FHI, with and into TriCo, with TriCo as the surviving corporation (the "merger"), pursuant to the Agreement and Plan of Reorganization and Merger, dated as of July 12, 2026, by and among FHI, TriCo and Merger Sub (the "merger agreement"), which collectively total 32,750,000, multiplied by (ii) the exchange ratio of 2.095 shares of FHI common stock for each share of TriCo common stock.

Estimated solely for the purpose of calculating the registration fee required by Section 6(b) of the Securities Act of 1933, as amended (the "Securities Act"), and calculated in accordance with Rules 457(c) and 457(f)(1) promulgated thereunder. The maximum aggregate offering price is (i) the average of the high and low prices of TriCo common stock as reported on the Nasdaq Global Select Market on August 27, 2026 ($53.6325 per share), multiplied by (ii) the estimated maximum number of shares of TriCo common stock to be converted or exchanged in the merger (32,750,000).</ffd:OfferingNote>
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