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<xbrl
  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"
  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/2026/ffd-2026.xsd"
      xlink:type="simple"/>
    <context id="rc">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001833936</identifier>
        </entity>
        <period>
            <startDate>2026-10-28</startDate>
            <endDate>2026-10-28</endDate>
        </period>
    </context>
    <context id="offrl_1">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001833936</identifier>
            <segment>
                <xbrldi:typedMember dimension="ffd:OfferingAxis">
                    <dei:lineNo>1</dei:lineNo>
                </xbrldi:typedMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-10-28</startDate>
            <endDate>2026-10-28</endDate>
        </period>
    </context>
    <unit id="USD">
        <measure>iso4217:USD</measure>
    </unit>
    <ffd:FormTp contextRef="rc" id="ixv-150">SC TO</ffd:FormTp>
    <ffd:SubmissnTp contextRef="rc" id="ixv-151">SC TO-I/A</ffd:SubmissnTp>
    <ffd:FeeExhibitTp contextRef="rc" id="ixv-152">EX-FILING FEES</ffd:FeeExhibitTp>
    <dei:EntityCentralIndexKey contextRef="rc" id="ixv-153">0001833936</dei:EntityCentralIndexKey>
    <dei:EntityRegistrantName contextRef="rc" id="ixv-154">BlackRock Alpha Strategies Fund</dei:EntityRegistrantName>
    <ffd:OfferingTableNa contextRef="rc" id="hiddenrcOfferingTableNa" xsi:nil="true"/>
    <ffd:OffsetTableNa contextRef="rc" id="hiddenrcOffsetTableNa">N/A</ffd:OffsetTableNa>
    <ffd:Rule011Flg contextRef="offrl_1" id="ixv-157">true</ffd:Rule011Flg>
    <ffd:PrevslyPdFlg contextRef="offrl_1" id="ixv-182">true</ffd:PrevslyPdFlg>
    <ffd:TxValtn
      contextRef="offrl_1"
      decimals="2"
      id="ixv-183"
      unitRef="USD">31690213.89</ffd:TxValtn>
    <ffd:FeeAmt
      contextRef="offrl_1"
      decimals="2"
      id="ixv-184"
      unitRef="USD">4376.42</ffd:FeeAmt>
    <ffd:TtlTxValtn contextRef="rc" decimals="2" id="ixv-185" unitRef="USD">31690213.89</ffd:TtlTxValtn>
    <ffd:TtlFeeAmt contextRef="rc" decimals="2" id="ixv-186" unitRef="USD">4376.42</ffd:TtlFeeAmt>
    <ffd:TtlPrevslyPdAmt contextRef="rc" decimals="2" id="ixv-187" unitRef="USD">4376.42</ffd:TtlPrevslyPdAmt>
    <ffd:TtlOffsetAmt contextRef="rc" decimals="2" id="ixv-188" unitRef="USD">0.00</ffd:TtlOffsetAmt>
    <ffd:NetFeeAmt contextRef="rc" decimals="2" id="ixv-189" unitRef="USD">0.00</ffd:NetFeeAmt>
    <ffd:OfferingNote contextRef="offrl_1" id="ixv-190">The transaction value is calculated as the aggregate maximum purchase price for Shares that could be purchased, based upon the net asset value of the Trust as of February 2, 2026. The fee of $4,376.42 was paid in connection with the filing of the Schedule TO-I by BlackRock Alpha Strategies Fund (File No. 005-92613) on March 24, 2026 (the "Schedule TO"). This is the final amendment to the Schedule TO and is being filed to report the results of the offer. The amount of filing fee is calculated at $138.10 per $1,000,000 of the transaction valuation in accordance with Rule 0-11 under the Securities Exchange Act of 1934, as amended, as modified by Fee Rate Advisory No. 1 for fiscal year 2026.</ffd:OfferingNote>
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