<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.24.1.1.u2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>225</ContextCount>
  <ElementCount>325</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>72</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>10</UnitCount>
  <MyReports>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>00090 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>00100 - Statement - Condensed Interim Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/StatementCondensedInterimConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Interim Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>00200 - Statement - Condensed Interim Consolidated Statements of Comprehensive Loss</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/StatementCondensedInterimConsolidatedStatementsOfComprehensiveLoss</Role>
      <ShortName>Condensed Interim Consolidated Statements of Comprehensive Loss</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>00300 - Statement - Condensed Interim Consolidated Statements of Changes in Equity (Deficit)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/StatementCondensedInterimConsolidatedStatementsOfChangesInEquityDeficit</Role>
      <ShortName>Condensed Interim Consolidated Statements of Changes in Equity (Deficit)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>00400 - Statement - Condensed Interim Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/StatementCondensedInterimConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Condensed Interim Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>10101 - Disclosure - Reporting Entity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureReportingEntity</Role>
      <ShortName>Reporting Entity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>10201 - Disclosure - Basis of presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureBasisOfPresentation</Role>
      <ShortName>Basis of presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>10301 - Disclosure - Material accounting policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureMaterialAccountingPolicies</Role>
      <ShortName>Material accounting policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>10401 - Disclosure - Recent accounting pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRecentAccountingPronouncements</Role>
      <ShortName>Recent accounting pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>10501 - Disclosure - Property, plant and equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosurePropertyPlantAndEquipment</Role>
      <ShortName>Property, plant and equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>10601 - Disclosure - Intangible assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureIntangibleAssets</Role>
      <ShortName>Intangible assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>10701 - Disclosure - Right-of-use assets and lease liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRightOfUseAssetsAndLeaseLiabilities</Role>
      <ShortName>Right-of-use assets and lease liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>10801 - Disclosure - Accounts payable and accrued liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureAccountsPayableAndAccruedLiabilities</Role>
      <ShortName>Accounts payable and accrued liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>10901 - Disclosure - Loans payable</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureLoansPayable</Role>
      <ShortName>Loans payable</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>11001 - Disclosure - Shareholder loans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureShareholderLoans</Role>
      <ShortName>Shareholder loans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>11101 - Disclosure - Other payables</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureOtherPayables</Role>
      <ShortName>Other payables</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>11201 - Disclosure - Deferred and contingent consideration</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureDeferredAndContingentConsideration</Role>
      <ShortName>Deferred and contingent consideration</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>11301 - Disclosure - Advance for research collaboration</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureAdvanceForResearchCollaboration</Role>
      <ShortName>Advance for research collaboration</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>11401 - Disclosure - Common shares</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureCommonShares</Role>
      <ShortName>Common shares</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>11501 - Disclosure - Contributed surplus</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureContributedSurplus</Role>
      <ShortName>Contributed surplus</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>11601 - Disclosure - Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureContingencies</Role>
      <ShortName>Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>11701 - Disclosure - Pensions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosurePensions</Role>
      <ShortName>Pensions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>11801 - Disclosure - Income taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureIncomeTaxes</Role>
      <ShortName>Income taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>11901 - Disclosure - Risk management arising from financial instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRiskManagementArisingFromFinancialInstruments</Role>
      <ShortName>Risk management arising from financial instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>12001 - Disclosure - Capital management</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureCapitalManagement</Role>
      <ShortName>Capital management</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>12101 - Disclosure - Related party transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRelatedPartyTransactions</Role>
      <ShortName>Related party transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>12201 - Disclosure - Basic and diluted loss per share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureBasicAndDilutedLossPerShare</Role>
      <ShortName>Basic and diluted loss per share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>12301 - Disclosure - Non-controlling interest</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureNonControllingInterest</Role>
      <ShortName>Non-controlling interest</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>12401 - Disclosure - Expenses by nature</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureExpensesByNature</Role>
      <ShortName>Expenses by nature</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>12501 - Disclosure - Subsequent events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>20302 - Disclosure - Material accounting policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureMaterialAccountingPoliciesPolicies</Role>
      <ShortName>Material accounting policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>30503 - Disclosure - Property, plant and equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosurePropertyPlantAndEquipmentTables</Role>
      <ShortName>Property, plant and equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosurePropertyPlantAndEquipment</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>30603 - Disclosure - Intangible assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureIntangibleAssetsTables</Role>
      <ShortName>Intangible assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureIntangibleAssets</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>30703 - Disclosure - Right-of-use assets and lease liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRightOfUseAssetsAndLeaseLiabilitiesTables</Role>
      <ShortName>Right-of-use assets and lease liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureRightOfUseAssetsAndLeaseLiabilities</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>30803 - Disclosure - Accounts payable and accrued liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureAccountsPayableAndAccruedLiabilitiesTables</Role>
      <ShortName>Accounts payable and accrued liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureAccountsPayableAndAccruedLiabilities</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>30903 - Disclosure - Loans payable (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureLoansPayableTables</Role>
      <ShortName>Loans payable (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureLoansPayable</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>31103 - Disclosure - Other payables (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureOtherPayablesTables</Role>
      <ShortName>Other payables (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureOtherPayables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>31203 - Disclosure - Deferred and contingent consideration (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureDeferredAndContingentConsiderationTables</Role>
      <ShortName>Deferred and contingent consideration (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureDeferredAndContingentConsideration</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>31303 - Disclosure - Advance for research collaboration (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureAdvanceForResearchCollaborationTables</Role>
      <ShortName>Advance for research collaboration (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureAdvanceForResearchCollaboration</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>31403 - Disclosure - Common shares (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureCommonSharesTables</Role>
      <ShortName>Common shares (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureCommonShares</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>31503 - Disclosure - Contributed surplus (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureContributedSurplusTables</Role>
      <ShortName>Contributed surplus (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureContributedSurplus</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>31903 - Disclosure - Risk management arising from financial instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRiskManagementArisingFromFinancialInstrumentsTables</Role>
      <ShortName>Risk management arising from financial instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureRiskManagementArisingFromFinancialInstruments</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>32203 - Disclosure - Basic and diluted loss per share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureBasicAndDilutedLossPerShareTables</Role>
      <ShortName>Basic and diluted loss per share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureBasicAndDilutedLossPerShare</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>32303 - Disclosure - Non-controlling interest (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureNonControllingInterestTables</Role>
      <ShortName>Non-controlling interest (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureNonControllingInterest</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>32403 - Disclosure - Expenses by nature (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureExpensesByNatureTables</Role>
      <ShortName>Expenses by nature (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureExpensesByNature</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>40201 - Disclosure - Basis of presentation - Going concern (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureBasisOfPresentationGoingConcernDetails</Role>
      <ShortName>Basis of presentation - Going concern (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>40202 - Disclosure - Basis of presentation - Going concern - Credit Facility (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureBasisOfPresentationGoingConcernCreditFacilityDetails</Role>
      <ShortName>Basis of presentation - Going concern - Credit Facility (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>40203 - Disclosure - Basis of presentation - Going Concern - Private Placement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureBasisOfPresentationGoingConcernPrivatePlacementDetails</Role>
      <ShortName>Basis of presentation - Going Concern - Private Placement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>40204 - Disclosure - Basis of presentation - Going concern - Alumni Purchase Agreement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureBasisOfPresentationGoingConcernAlumniPurchaseAgreementDetails</Role>
      <ShortName>Basis of presentation - Going concern - Alumni Purchase Agreement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>40205 - Disclosure - Basis of presentation - Going concern - February 2024 Public Offering (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureBasisOfPresentationGoingConcernFebruary2024PublicOfferingDetails</Role>
      <ShortName>Basis of presentation - Going concern - February 2024 Public Offering (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>40501 - Disclosure - Property, Plant and equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosurePropertyPlantAndEquipmentDetails</Role>
      <ShortName>Property, Plant and equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>40601 - Disclosure - Intangible assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureIntangibleAssetsDetails</Role>
      <ShortName>Intangible assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureIntangibleAssetsTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>40701 - Disclosure - Right-of-use assets and lease liabilities - Narratives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRightOfUseAssetsAndLeaseLiabilitiesNarrativesDetails</Role>
      <ShortName>Right-of-use assets and lease liabilities - Narratives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>40702 - Disclosure - Right-of-use assets and lease liabilities - Finance Right-of-use assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRightOfUseAssetsAndLeaseLiabilitiesFinanceRightOfUseAssetsDetails</Role>
      <ShortName>Right-of-use assets and lease liabilities - Finance Right-of-use assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>40703 - Disclosure - Right-of-use assets and lease liabilities - Finance Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRightOfUseAssetsAndLeaseLiabilitiesFinanceLeaseLiabilitiesDetails</Role>
      <ShortName>Right-of-use assets and lease liabilities - Finance Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>40704 - Disclosure - Right-of-use assets and lease liabilities - Operating Right-of-use assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRightOfUseAssetsAndLeaseLiabilitiesOperatingRightOfUseAssetsDetails</Role>
      <ShortName>Right-of-use assets and lease liabilities - Operating Right-of-use assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>40705 - Disclosure - Right-of-use assets and lease liabilities - Operating Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRightOfUseAssetsAndLeaseLiabilitiesOperatingLeaseLiabilitiesDetails</Role>
      <ShortName>Right-of-use assets and lease liabilities - Operating Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>40801 - Disclosure - Accounts payable and accrued liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureAccountsPayableAndAccruedLiabilitiesDetails</Role>
      <ShortName>Accounts payable and accrued liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureAccountsPayableAndAccruedLiabilitiesTables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>40901 - Disclosure - Loans payable - Bank Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureLoansPayableBankLoansDetails</Role>
      <ShortName>Loans payable - Bank Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>40903 - Disclosure - Loans payable - TMS Device Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureLoansPayableTmsDeviceLoansDetails</Role>
      <ShortName>Loans payable - TMS Device Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>40904 - Disclosure - Loans payable - Madryn Credit Facility (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureLoansPayableMadrynCreditFacilityDetails</Role>
      <ShortName>Loans payable - Madryn Credit Facility (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>40905 - Disclosure - Loans payable - Promissory Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureLoansPayablePromissoryNotesDetails</Role>
      <ShortName>Loans payable - Promissory Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>40906 - Disclosure - Loans payable - Neuronetics Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureLoansPayableNeuroneticsNotesDetails</Role>
      <ShortName>Loans payable - Neuronetics Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>40907 - Disclosure - Loans payable - Non-controlling interest loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureLoansPayableNonControllingInterestLoansDetails</Role>
      <ShortName>Loans payable - Non-controlling interest loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>41001 - Disclosure - Shareholder loans - Klein Note (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureShareholderLoansKleinNoteDetails</Role>
      <ShortName>Shareholder loans - Klein Note (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>41002 - Disclosure - Shareholder loans - 2023 and Greybrook Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureShareholderLoans2023AndGreybrookNotesDetails</Role>
      <ShortName>Shareholder loans - 2023 and Greybrook Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>41003 - Disclosure - Shareholder loans - Subordinated Convertible Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureShareholderLoansSubordinatedConvertibleNotesDetails</Role>
      <ShortName>Shareholder loans - Subordinated Convertible Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>41101 - Disclosure - Other payables - Lender Warrants (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureOtherPayablesLenderWarrantsDetails</Role>
      <ShortName>Other payables - Lender Warrants (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>41102 - Disclosure - Other payables - Share Units (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureOtherPayablesShareUnitsDetails</Role>
      <ShortName>Other payables - Share Units (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>41103 - Disclosure - Other payables - Device Contract Termination (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureOtherPayablesDeviceContractTerminationDetails</Role>
      <ShortName>Other payables - Device Contract Termination (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>41104 - Disclosure - Other payables - Klein Note Settlement payable (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureOtherPayablesKleinNoteSettlementPayableDetails</Role>
      <ShortName>Other payables - Klein Note Settlement payable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>41201 - Disclosure - Deferred and contingent consideration (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureDeferredAndContingentConsiderationDetails</Role>
      <ShortName>Deferred and contingent consideration (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureDeferredAndContingentConsiderationTables</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>41301 - Disclosure - Advance for research collaboration (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureAdvanceForResearchCollaborationDetails</Role>
      <ShortName>Advance for research collaboration (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureAdvanceForResearchCollaborationTables</ParentRole>
      <Position>73</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>41401 - Disclosure - Common shares - Changes in common shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureCommonSharesChangesInCommonSharesDetails</Role>
      <ShortName>Common shares - Changes in common shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>41402 - Disclosure - Common shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureCommonSharesDetails</Role>
      <ShortName>Common shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureCommonSharesTables</ParentRole>
      <Position>75</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>41501 - Disclosure - Contributed surplus - Stock Options Narratives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureContributedSurplusStockOptionsNarrativesDetails</Role>
      <ShortName>Contributed surplus - Stock Options Narratives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>41502 - Disclosure - Contributed surplus - Stock Options Outstanding (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureContributedSurplusStockOptionsOutstandingDetails</Role>
      <ShortName>Contributed surplus - Stock Options Outstanding (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>41503 - Disclosure - Contributed surplus - Stock Options - Additional Narratives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureContributedSurplusStockOptionsAdditionalNarrativesDetails</Role>
      <ShortName>Contributed surplus - Stock Options - Additional Narratives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>41504 - Disclosure - Contributed surplus - Greybrook Warrants (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureContributedSurplusGreybrookWarrantsDetails</Role>
      <ShortName>Contributed surplus - Greybrook Warrants (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>41601 - Disclosure - Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureContingenciesDetails</Role>
      <ShortName>Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureContingencies</ParentRole>
      <Position>80</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>41701 - Disclosure - Pensions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosurePensionsDetails</Role>
      <ShortName>Pensions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosurePensions</ParentRole>
      <Position>81</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>41901 - Disclosure - Risk management arising from financial instruments - Aging schedule in respect of accounts receivable balance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRiskManagementArisingFromFinancialInstrumentsAgingScheduleInRespectOfAccountsReceivableBalanceDetails</Role>
      <ShortName>Risk management arising from financial instruments - Aging schedule in respect of accounts receivable balance (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>41902 - Disclosure - Risk management arising from financial instruments - Interest rate risk (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRiskManagementArisingFromFinancialInstrumentsInterestRateRiskDetails</Role>
      <ShortName>Risk management arising from financial instruments - Interest rate risk (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>42101 - Disclosure - Related party transactions - Transactions with significant shareholder - Greybrook Health (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRelatedPartyTransactionsTransactionsWithSignificantShareholderGreybrookHealthDetails</Role>
      <ShortName>Related party transactions - Transactions with significant shareholder - Greybrook Health (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>42102 - Disclosure - Related party transactions - Loans from shareholder - Greybrook Health (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRelatedPartyTransactionsLoansFromShareholderGreybrookHealthDetails</Role>
      <ShortName>Related party transactions - Loans from shareholder - Greybrook Health (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>42103 - Disclosure - Related party transactions - Transactions with the significant shareholder, officer and director - Benjamin Klein (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRelatedPartyTransactionsTransactionsWithSignificantShareholderOfficerAndDirectorBenjaminKleinDetails</Role>
      <ShortName>Related party transactions - Transactions with the significant shareholder, officer and director - Benjamin Klein (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>42104 - Disclosure - Related party transactions - Loan from significant shareholder, officer and director - Benjamin Klein (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRelatedPartyTransactionsLoanFromSignificantShareholderOfficerAndDirectorBenjaminKleinDetails</Role>
      <ShortName>Related party transactions - Loan from significant shareholder, officer and director - Benjamin Klein (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>42105 - Disclosure - Related party transactions - Loans from shareholders and officers (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRelatedPartyTransactionsLoansFromShareholdersAndOfficersDetails</Role>
      <ShortName>Related party transactions - Loans from shareholders and officers (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>88</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>42106 - Disclosure - Related party transactions - Loan from significant shareholder - Madryn (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureRelatedPartyTransactionsLoanFromSignificantShareholderMadrynDetails</Role>
      <ShortName>Related party transactions - Loan from significant shareholder - Madryn (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>42201 - Disclosure - Basic and diluted loss per share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureBasicAndDilutedLossPerShareDetails</Role>
      <ShortName>Basic and diluted loss per share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureBasicAndDilutedLossPerShareTables</ParentRole>
      <Position>90</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>42202 - Disclosure - Basic and diluted loss per share - Antidilutive securities excluded from diluted calculation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureBasicAndDilutedLossPerShareAntidilutiveSecuritiesExcludedFromDilutedCalculationDetails</Role>
      <ShortName>Basic and diluted loss per share - Antidilutive securities excluded from diluted calculation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>42301 - Disclosure - Non-controlling interest (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureNonControllingInterestDetails</Role>
      <ShortName>Non-controlling interest (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureNonControllingInterestTables</ParentRole>
      <Position>92</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>42302 - Disclosure - Non-controlling interest - Schedule of balance sheet financial information of non-controlling interest (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureNonControllingInterestScheduleOfBalanceSheetFinancialInformationOfNonControllingInterestDetails</Role>
      <ShortName>Non-controlling interest - Schedule of balance sheet financial information of non-controlling interest (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>42303 - Disclosure - Non-controlling interest - Schedule of comprehensive loss financial information of non-controlling interest (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureNonControllingInterestScheduleOfComprehensiveLossFinancialInformationOfNonControllingInterestDetails</Role>
      <ShortName>Non-controlling interest - Schedule of comprehensive loss financial information of non-controlling interest (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>42401 - Disclosure - Expenses by nature - Other regional and center support costs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureExpensesByNatureOtherRegionalAndCenterSupportCostsDetails</Role>
      <ShortName>Expenses by nature - Other regional and center support costs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>42402 - Disclosure - Expenses by nature (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureExpensesByNatureDetails</Role>
      <ShortName>Expenses by nature (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureExpensesByNatureTables</ParentRole>
      <Position>96</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>42501 - Disclosure - Subsequent events (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.greenbrooktms.com/role/DisclosureSubsequentEventsDetails</Role>
      <ShortName>Subsequent events (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.greenbrooktms.com/role/DisclosureSubsequentEvents</ParentRole>
      <Position>97</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Uncategorized</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="gbnh-20240331x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 10 fact(s) appearing in ix:hidden were eligible for transformation: gbnh:ClassOfWarrantOrRightThresholdTradingDays, us-gaap:EarningsPerShareDiluted, us-gaap:NetIncomeLossAvailableToCommonStockholdersDiluted, us-gaap:PreferredStockSharesOutstanding, us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding -  gbnh-20240331x10q.htm 9</Log>
    <Log type="Warning">[ix-0514-Hidden-Fact-Not-Referenced] WARN: 2 fact(s) appearing in ix:hidden were not referenced by any -sec-ix-hidden style property: us-gaap:CommitmentsAndContingencies -  gbnh-20240331x10q.htm 9</Log>
    <Log type="Warning">[dq-0712-Presentation-Base-Set-Order] Role '42501 - Disclosure - Subsequent events (Details)', a level 4, Detail role, appears before '995410 - Disclosure - Pay vs Performance Disclosure', a level 1, Note role. gbnh-20240331.xsd 303, https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd 30</Log>
  </Logs>
  <InputFiles>
    <File>gbnh-20240331.xsd</File>
    <File>gbnh-20240331_cal.xml</File>
    <File>gbnh-20240331_def.xml</File>
    <File>gbnh-20240331_lab.xml</File>
    <File>gbnh-20240331_pre.xml</File>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="gbnh-20240331x10q.htm">gbnh-20240331x10q.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="593">http://fasb.org/us-gaap/2023</BaseTaxonomy>
    <BaseTaxonomy items="27">http://xbrl.sec.gov/dei/2023</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2023</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
