<?xml version="1.0" encoding="utf-8"?>
<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">0001795815</identifier>
        </entity>
        <period>
            <startDate>2026-05-28</startDate>
            <endDate>2026-05-28</endDate>
        </period>
    </context>
    <context id="offrl_1">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001795815</identifier>
            <segment>
                <xbrldi:typedMember dimension="ffd:OfferingAxis">
                    <dei:lineNo>1</dei:lineNo>
                </xbrldi:typedMember>
            </segment>
        </entity>
        <period>
            <startDate>2026-05-28</startDate>
            <endDate>2026-05-28</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:FormTp contextRef="rc" id="ixv-168">S-8</ffd:FormTp>
    <ffd:SubmissnTp contextRef="rc" id="ixv-169">S-8</ffd:SubmissnTp>
    <ffd:FeeExhibitTp contextRef="rc" id="ixv-170">EX-FILING FEES</ffd:FeeExhibitTp>
    <dei:EntityCentralIndexKey contextRef="rc" id="ixv-171">0001795815</dei:EntityCentralIndexKey>
    <dei:EntityRegistrantName contextRef="rc" id="ixv-172">California BanCorp \ CA</dei:EntityRegistrantName>
    <ffd:OfferingTableNa contextRef="rc" id="hiddenrcOfferingTableNa" xsi:nil="true"/>
    <ffd:OffsetTableNa contextRef="rc" id="hiddenrcOffsetTableNa">N/A</ffd:OffsetTableNa>
    <ffd:PrevslyPdFlg contextRef="offrl_1" id="ixv-175">false</ffd:PrevslyPdFlg>
    <ffd:FormTp contextRef="rc" id="ixv-200">S-8</ffd:FormTp>
    <dei:EntityRegistrantName contextRef="rc" id="ixv-201">California BanCorp \ CA</dei:EntityRegistrantName>
    <ffd:OfferingSctyTp contextRef="offrl_1" id="ixv-202">Equity</ffd:OfferingSctyTp>
    <ffd:OfferingSctyTitl contextRef="offrl_1" id="ixv-203">Common Stock, no par value per share</ffd:OfferingSctyTitl>
    <ffd:FeesOthrRuleFlg contextRef="offrl_1" id="ixv-204">true</ffd:FeesOthrRuleFlg>
    <ffd:AmtSctiesRegd
      contextRef="offrl_1"
      decimals="0"
      id="ixv-205"
      unitRef="Shares">1600000</ffd:AmtSctiesRegd>
    <ffd:MaxOfferingPricPerScty
      contextRef="offrl_1"
      decimals="2"
      id="ixv-206"
      unitRef="USD">19.15</ffd:MaxOfferingPricPerScty>
    <ffd:MaxAggtOfferingPric
      contextRef="offrl_1"
      decimals="2"
      id="ixv-207"
      unitRef="USD">30640000.00</ffd:MaxAggtOfferingPric>
    <ffd:FeeRate
      contextRef="offrl_1"
      decimals="7"
      id="ixv-208"
      unitRef="pure">0.0001381</ffd:FeeRate>
    <ffd:FeeAmt
      contextRef="offrl_1"
      decimals="2"
      id="ixv-209"
      unitRef="USD">4231.38</ffd:FeeAmt>
    <ffd:TtlOfferingAmt contextRef="rc" decimals="2" id="ixv-210" unitRef="USD">30640000.00</ffd:TtlOfferingAmt>
    <ffd:TtlFeeAmt contextRef="rc" decimals="2" id="ixv-211" unitRef="USD">4231.38</ffd:TtlFeeAmt>
    <ffd:TtlOffsetAmt contextRef="rc" decimals="2" id="ixv-212" unitRef="USD">0.00</ffd:TtlOffsetAmt>
    <ffd:NetFeeAmt contextRef="rc" decimals="2" id="ixv-213" unitRef="USD">4231.38</ffd:NetFeeAmt>
    <ffd:OfferingNote contextRef="offrl_1" id="ixv-214">(1) Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the "Securities Act"), this registration statement shall also cover any additional shares of the Registrant's common stock, no par value per share (the "Common Stock"), that become issuable under the California BanCorp 2026 Omnibus Equity Incentive Plan by reason of any stock dividend, stock split, recapitalization or any other similar transaction effected without the Registrant's receipt of consideration which results in an increase in the number of outstanding shares of Common Stock.

(2) For purposes of computing the registration fee only. Pursuant to Rule 457(c) and (h), the Proposed Maximum Offering Price Per Share is based upon the average of the high and low prices for the Registrant's Common Stock on the Nasdaq Capital Market on May 27, 2026.</ffd:OfferingNote>
</xbrl>
