<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.0.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>145</ContextCount>
  <ElementCount>354</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>40</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-document-and-entity-information</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>001 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-consolidated-balance-sheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>002 - Statement - Consolidated Balance Sheets (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-consolidated-balance-sheets-parentheticals</Role>
      <ShortName>Consolidated Balance Sheets (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>003 - Statement - Consolidated Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-consolidated-statements-of-operations</Role>
      <ShortName>Consolidated Statements of Operations</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>004 - Statement - Consolidated Statements of Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-consolidated-statements-of-comprehensive-income-loss</Role>
      <ShortName>Consolidated Statements of Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>005 - Statement - Consolidated Statements of Shareholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-consolidated-statements-of-shareholders-equity</Role>
      <ShortName>Consolidated Statements of Shareholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>006 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-consolidated-statements-of-cash-flows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>007 - Disclosure - Note 1 - Organization</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-1-organization</Role>
      <ShortName>Note 1 - Organization</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>008 - Disclosure - Note 2 - Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-2-significant-accounting-policies</Role>
      <ShortName>Note 2 - Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>009 - Disclosure - Note 3 - Revenue</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-3-revenue</Role>
      <ShortName>Note 3 - Revenue</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>010 - Disclosure - Note 4 - Property and Equipment and Building Construction in Progress</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-4-property-and-equipment-and-building-construction-in-progress</Role>
      <ShortName>Note 4 - Property and Equipment and Building Construction in Progress</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>011 - Disclosure - Note 5 - Accrued Expenses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-5-accrued-expenses</Role>
      <ShortName>Note 5 - Accrued Expenses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>012 - Disclosure - Note 6 - Common Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-6-common-stock</Role>
      <ShortName>Note 6 - Common Stock</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>013 - Disclosure - Note 7 - Common Stock Options</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-7-common-stock-options</Role>
      <ShortName>Note 7 - Common Stock Options</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>014 - Disclosure - Note 8 - Net Income Loss Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-8-net-income-loss-per-share</Role>
      <ShortName>Note 8 - Net Income Loss Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>015 - Disclosure - Note 9 - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-9-income-taxes</Role>
      <ShortName>Note 9 - Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>016 - Disclosure - Note 10 - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-10-subsequent-events</Role>
      <ShortName>Note 10 - Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>017 - Disclosure - Note 11 - Selected Quarterly Financial Data (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-11-selected-quarterly-financial-data-unaudited</Role>
      <ShortName>Note 11 - Selected Quarterly Financial Data (Unaudited)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>018 - Disclosure - Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-significant-accounting-policies-policies</Role>
      <ShortName>Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-2-significant-accounting-policies</ParentRole>
      <Position>19</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>019 - Disclosure - Note 2 - Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-2-significant-accounting-policies-tables</Role>
      <ShortName>Note 2 - Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-2-significant-accounting-policies</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>020 - Disclosure - Note 4 - Property and Equipment and Building Construction in Progress (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-4-property-and-equipment-and-building-construction-in-progress-tables</Role>
      <ShortName>Note 4 - Property and Equipment and Building Construction in Progress (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-4-property-and-equipment-and-building-construction-in-progress</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>021 - Disclosure - Note 5 - Accrued Expenses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-5-accrued-expenses-tables</Role>
      <ShortName>Note 5 - Accrued Expenses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-5-accrued-expenses</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>022 - Disclosure - Note 7 - Common Stock Options (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-7-common-stock-options-tables</Role>
      <ShortName>Note 7 - Common Stock Options (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-7-common-stock-options</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>023 - Disclosure - Note 8 - Net Income Loss Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-8-net-income-loss-per-share-tables</Role>
      <ShortName>Note 8 - Net Income Loss Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-8-net-income-loss-per-share</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>024 - Disclosure - Note 9 - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-9-income-taxes-tables</Role>
      <ShortName>Note 9 - Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-9-income-taxes</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>025 - Disclosure - Note 11 - Selected Quarterly Financial Data (Unaudited) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-11-selected-quarterly-financial-data-unaudited-tables</Role>
      <ShortName>Note 11 - Selected Quarterly Financial Data (Unaudited) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-11-selected-quarterly-financial-data-unaudited</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>026 - Disclosure - Note 1 - Organization (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-1-organization-details-textual</Role>
      <ShortName>Note 1 - Organization (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-1-organization</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>027 - Disclosure - Note 2 - Significant Accounting Policies (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-2-significant-accounting-policies-details-textual</Role>
      <ShortName>Note 2 - Significant Accounting Policies (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-2-significant-accounting-policies-tables</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>028 - Disclosure - Note 2 - Significant Accounting Policies - Share-based Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-2-significant-accounting-policies-sharebased-compensation-expense-details</Role>
      <ShortName>Note 2 - Significant Accounting Policies - Share-based Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>029 - Disclosure - Note 2 - Significant Accounting Policies - Stock Option Valuation Assumptions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-2-significant-accounting-policies-stock-option-valuation-assumptions-details</Role>
      <ShortName>Note 2 - Significant Accounting Policies - Stock Option Valuation Assumptions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>030 - Disclosure - Note 3 - Revenue (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-3-revenue-details-textual</Role>
      <ShortName>Note 3 - Revenue (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-3-revenue</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>031 - Disclosure - Note 4 - Property and Equipment and Building Construction in Progress (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-4-property-and-equipment-and-building-construction-in-progress-details-textual</Role>
      <ShortName>Note 4 - Property and Equipment and Building Construction in Progress (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-4-property-and-equipment-and-building-construction-in-progress-tables</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>032 - Disclosure - Note 4 - Property and Equipment and Building Construction in Progress - Property and Equipment, Net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-4-property-and-equipment-and-building-construction-in-progress-property-and-equipment-net-details</Role>
      <ShortName>Note 4 - Property and Equipment and Building Construction in Progress - Property and Equipment, Net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>033 - Disclosure - Note 5 - Accrued Expenses - Accrued Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-5-accrued-expenses-accrued-expenses-details</Role>
      <ShortName>Note 5 - Accrued Expenses - Accrued Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>034 - Disclosure - Note 6 - Common Stock (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-6-common-stock-details-textual</Role>
      <ShortName>Note 6 - Common Stock (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-6-common-stock</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>035 - Disclosure - Note 7 - Common Stock Options (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-7-common-stock-options-details-textual</Role>
      <ShortName>Note 7 - Common Stock Options (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-7-common-stock-options-tables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>036 - Disclosure - Note 7 - Common Stock Options - Changes in Common Stock Options Issued (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-7-common-stock-options-changes-in-common-stock-options-issued-details</Role>
      <ShortName>Note 7 - Common Stock Options - Changes in Common Stock Options Issued (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>037 - Disclosure - Note 8 - Net Income Loss Per Share - Computation of Basic and Diluted Net Loss Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-8-net-income-loss-per-share-computation-of-basic-and-diluted-net-loss-per-share-details</Role>
      <ShortName>Note 8 - Net Income Loss Per Share - Computation of Basic and Diluted Net Loss Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>038 - Disclosure - Note 8 - Net Income Loss Per Share - Potentially Dilutive Securities Outstanding (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-8-net-income-loss-per-share-potentially-dilutive-securities-outstanding-details</Role>
      <ShortName>Note 8 - Net Income Loss Per Share - Potentially Dilutive Securities Outstanding (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>039 - Disclosure - Note 9 - Income Taxes (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-9-income-taxes-details-textual</Role>
      <ShortName>Note 9 - Income Taxes (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-9-income-taxes-tables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>040 - Disclosure - Note 9 - Income Taxes - Components of Income Before Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-9-income-taxes-components-of-income-before-income-taxes-details</Role>
      <ShortName>Note 9 - Income Taxes - Components of Income Before Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>041 - Disclosure - Note 9 - Income Taxes - Income Tax from Continuing Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-9-income-taxes-income-tax-from-continuing-operations-details</Role>
      <ShortName>Note 9 - Income Taxes - Income Tax from Continuing Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>042 - Disclosure - Note 9 - Income Taxes - Reconciliation of Canadian Federal Statutory Income Tax Rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-9-income-taxes-reconciliation-of-canadian-federal-statutory-income-tax-rate-details</Role>
      <ShortName>Note 9 - Income Taxes - Reconciliation of Canadian Federal Statutory Income Tax Rate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>043 - Disclosure - Note 9 - Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-9-income-taxes-significant-components-of-deferred-tax-assets-and-liabilities-details</Role>
      <ShortName>Note 9 - Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>044 - Disclosure - Note 9 - Income Taxes - Reconciliation of Unrecognized Tax Benefit Balances (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-9-income-taxes-reconciliation-of-unrecognized-tax-benefit-balances-details</Role>
      <ShortName>Note 9 - Income Taxes - Reconciliation of Unrecognized Tax Benefit Balances (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>045 - Disclosure - Note 10 - Subsequent Events (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-10-subsequent-events-details-textual</Role>
      <ShortName>Note 10 - Subsequent Events (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-10-subsequent-events</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="xbit20211231_10k.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>046 - Disclosure - Note 11 - Selected Quarterly Financial Data (Unaudited) - Quarterly Financial Data (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbiotech.com/20211231/role/statement-note-11-selected-quarterly-financial-data-unaudited-quarterly-financial-data-details</Role>
      <ShortName>Note 11 - Selected Quarterly Financial Data (Unaudited) - Quarterly Financial Data (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://xbiotech.com/20211231/role/statement-note-11-selected-quarterly-financial-data-unaudited-tables</ParentRole>
      <Position>47</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-K" original="xbit20211231_10k.htm">xbit20211231_10k.htm</File>
    <File>ex_345369.htm</File>
    <File>ex_345370.htm</File>
    <File>ex_345371.htm</File>
    <File>ex_345375.htm</File>
    <File>ex_345380.htm</File>
    <File>ex_345381.htm</File>
    <File>ex_345538.htm</File>
    <File>xbit-20211231.xsd</File>
    <File>xbit-20211231_cal.xml</File>
    <File>xbit-20211231_def.xml</File>
    <File>xbit-20211231_lab.xml</File>
    <File>xbit-20211231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>pipe.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="658">http://fasb.org/us-gaap/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy items="35">http://xbrl.sec.gov/dei/2021q4</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
