<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2025"
  xmlns:ffd="http://xbrl.sec.gov/ffd/2025"
  xmlns:iso4217="http://www.xbrl.org/2003/iso4217"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xbrldi="http://xbrl.org/2006/xbrldi"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <link:schemaRef
      xlink:href="https://xbrl.sec.gov/ffd/2025/ffd-2025.xsd"
      xlink:type="simple"/>
    <context id="c_offering_1">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000729580</identifier>
            <segment>
                <xbrldi:typedMember dimension="ffd:OfferingAxis">
                    <dei:lineNo>1</dei:lineNo>
                </xbrldi:typedMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-05-14</startDate>
            <endDate>2026-05-14</endDate>
        </period>
    </context>
    <context id="c_offering_2">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000729580</identifier>
            <segment>
                <xbrldi:typedMember dimension="ffd:OfferingAxis">
                    <dei:lineNo>2</dei:lineNo>
                </xbrldi:typedMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-05-14</startDate>
            <endDate>2026-05-14</endDate>
        </period>
    </context>
    <context id="c_report">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000729580</identifier>
        </entity>
        <period>
            <startDate>2026-05-14</startDate>
            <endDate>2026-05-14</endDate>
        </period>
    </context>
    <unit id="USD">
        <measure>iso4217:USD</measure>
    </unit>
    <unit id="pure">
        <measure>pure</measure>
    </unit>
    <unit id="shares">
        <measure>shares</measure>
    </unit>
    <ffd:SubmissnTp contextRef="c_report" id="fee_001">424B5</ffd:SubmissnTp>
    <ffd:FeeExhibitTp contextRef="c_report" id="fee_002">EX-FILING FEES</ffd:FeeExhibitTp>
    <dei:EntityCentralIndexKey contextRef="c_report" id="fee_003">0000729580</dei:EntityCentralIndexKey>
    <ffd:RegnFileNb contextRef="c_report" id="fee_004">333-295813</ffd:RegnFileNb>
    <ffd:OfferingTableNa contextRef="c_report" id="fee_005" xsi:nil="true"/>
    <ffd:OffsetTableNa contextRef="c_report" id="fee_006">N/A</ffd:OffsetTableNa>
    <ffd:CombinedProspectusTableNa contextRef="c_report" id="fee_007">N/A</ffd:CombinedProspectusTableNa>
    <ffd:FormTp contextRef="c_report" id="fee_008">S-3</ffd:FormTp>
    <dei:EntityRegistrantName contextRef="c_report" id="fee_009">BEL FUSE INC /NJ</dei:EntityRegistrantName>
    <ffd:PrevslyPdFlg contextRef="c_offering_1" id="fee_010">false</ffd:PrevslyPdFlg>
    <ffd:OfferingSctyTp contextRef="c_offering_1" id="fee_011">Equity</ffd:OfferingSctyTp>
    <ffd:OfferingSctyTitl contextRef="c_offering_1" id="fee_012">Class B common stock, par value $0.10 per share</ffd:OfferingSctyTitl>
    <ffd:Rule457rFlg contextRef="c_offering_1" id="fee_013">true</ffd:Rule457rFlg>
    <ffd:AmtSctiesRegd
      contextRef="c_offering_1"
      decimals="0"
      id="fee_014"
      unitRef="shares">1725000</ffd:AmtSctiesRegd>
    <ffd:MaxAggtOfferingPric
      contextRef="c_offering_1"
      decimals="INF"
      id="fee_015"
      unitRef="USD">458850000.00</ffd:MaxAggtOfferingPric>
    <ffd:FeeRate
      contextRef="c_offering_1"
      decimals="INF"
      id="fee_016"
      unitRef="pure">0.0001381</ffd:FeeRate>
    <ffd:FeeAmt
      contextRef="c_offering_1"
      decimals="INF"
      id="ixv-256"
      unitRef="USD">63367.19</ffd:FeeAmt>
    <ffd:PrevslyPdFlg contextRef="c_offering_2" id="fee_017">true</ffd:PrevslyPdFlg>
    <ffd:OfferingSctyTp contextRef="c_offering_2" id="fee_018">Equity</ffd:OfferingSctyTp>
    <ffd:OfferingSctyTitl contextRef="c_offering_2" id="fee_019">Class B common stock, par value $0.10 per share</ffd:OfferingSctyTitl>
    <ffd:Rule457rFlg contextRef="c_offering_2" id="fee_020">true</ffd:Rule457rFlg>
    <ffd:FeeAmt
      contextRef="c_offering_2"
      decimals="INF"
      id="ixv-261"
      unitRef="USD">0.00</ffd:FeeAmt>
    <ffd:TtlOfferingAmt
      contextRef="c_report"
      decimals="INF"
      id="ixv-262"
      unitRef="USD">458850000.00</ffd:TtlOfferingAmt>
    <ffd:TtlFeeAmt
      contextRef="c_report"
      decimals="INF"
      id="ixv-263"
      unitRef="USD">63367.19</ffd:TtlFeeAmt>
    <ffd:TtlPrevslyPdAmt
      contextRef="c_report"
      decimals="INF"
      id="ixv-264"
      unitRef="USD">0.00</ffd:TtlPrevslyPdAmt>
    <ffd:TtlOffsetAmt
      contextRef="c_report"
      decimals="INF"
      id="ixv-265"
      unitRef="USD">0.00</ffd:TtlOffsetAmt>
    <ffd:NetFeeAmt
      contextRef="c_report"
      decimals="INF"
      id="ixv-266"
      unitRef="USD">63367.19</ffd:NetFeeAmt>
    <ffd:OfferingNote contextRef="c_offering_1" id="ixv-267">The registration fee is calculated in accordance with Rule 457(o) under the Securities Act of 1933, as amended (the "Securities Act"). This "Calculation of Filing Fee Tables" table shall be deemed to update the "Calculation of Registration Fee" table in the registrant's Registration Statement on Form S-3ASR (File No. 333- 295813) in accordance with Rule 456(b), 457(o) and 457(r) under the Securities Act.</ffd:OfferingNote>
    <ffd:OfferingNote contextRef="c_offering_2" id="ixv-268">The registration fee is calculated in accordance with Rule 457(o) under the Securities Act of 1933, as amended (the "Securities Act"). This "Calculation of Filing Fee Tables" table shall be deemed to update the "Calculation of Registration Fee" table in the registrant's Registration Statement on Form S-3ASR (File No. 333- 295813) in accordance with Rule 456(b), 457(o) and 457(r) under the Securities Act.</ffd:OfferingNote>
</xbrl>
