<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.24.1.1.u2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>211</ContextCount>
  <ElementCount>290</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>66</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>0000002 - Statement - Consolidated Balance Sheets - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ConsolidatedBalanceSheets10K</Role>
      <ShortName>Consolidated Balance Sheets - 10K</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>0000003 - Statement - Consolidated Balance Sheets (Parenthetical) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ConsolidatedBalanceSheetsParenthetical10K</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical) - 10K</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>0000004 - Statement - Consolidated Statements of Operations - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ConsolidatedStatementsofOperations10K</Role>
      <ShortName>Consolidated Statements of Operations - 10K</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>0000005 - Statement - Consolidated Statements of Cash Flows - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ConsolidatedStatementsofCashFlows10K</Role>
      <ShortName>Consolidated Statements of Cash Flows - 10K</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>0000006 - Statement - Consolidated Balance Sheets - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ConsolidatedBalanceSheetsQ1</Role>
      <ShortName>Consolidated Balance Sheets - Q1</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>0000007 - Statement - Consolidated Balance Sheets (Parenthetical) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ConsolidatedBalanceSheetsParentheticalQ1</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical) - Q1</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>0000008 - Statement - Consolidated Statements of Operations - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ConsolidatedStatementsofOperationsQ1</Role>
      <ShortName>Consolidated Statements of Operations - Q1</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>0000009 - Statement - Consolidated Statements of Changes in Stockholders??? Equity (Deficit) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ConsolidatedStatementsofChangesinStockholdersEquityDeficit10K</Role>
      <ShortName>Consolidated Statements of Changes in Stockholders??? Equity (Deficit) - 10K</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>0000010 - Statement - Consolidated Statements of Changes in Stockholders??? Equity (Deficit) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ConsolidatedStatementsofChangesinStockholdersEquityDeficitQ1</Role>
      <ShortName>Consolidated Statements of Changes in Stockholders??? Equity (Deficit) - Q1</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>0000011 - Statement - Consolidated Statements of Cash Flows - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ConsolidatedStatementsofCashFlowsQ1</Role>
      <ShortName>Consolidated Statements of Cash Flows - Q1</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>0000012 - Disclosure - ORGANIZATION AND DESCRIPTION OF BUSINESS - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ORGANIZATIONANDDESCRIPTIONOFBUSINESS10K</Role>
      <ShortName>ORGANIZATION AND DESCRIPTION OF BUSINESS - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>0000013 - Disclosure - LIQUIDITY - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/LIQUIDITY10K</Role>
      <ShortName>LIQUIDITY - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>0000014 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES10K</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>0000015 - Disclosure - MERGER WITH VALLON - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/MERGERWITHVALLON10K</Role>
      <ShortName>MERGER WITH VALLON - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>0000016 - Disclosure - FAIR VALUE MEASUREMENTS - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/FAIRVALUEMEASUREMENTS10K</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>0000017 - Disclosure - PROPERTY AND EQUIPMENT - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/PROPERTYANDEQUIPMENT10K</Role>
      <ShortName>PROPERTY AND EQUIPMENT - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>0000018 - Disclosure - LEASES - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/LEASES10K</Role>
      <ShortName>LEASES - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>0000019 - Disclosure - ACCRUED EXPENSES - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ACCRUEDEXPENSES10K</Role>
      <ShortName>ACCRUED EXPENSES - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>0000020 - Disclosure - PROMISSORY NOTES - 10K</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://gribio.com/role/PROMISSORYNOTES10K</Role>
      <ShortName>PROMISSORY NOTES - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>0000021 - Disclosure - STOCKHOLDERS EQUITY (DEFICIT) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKHOLDERSEQUITYDEFICIT10K</Role>
      <ShortName>STOCKHOLDERS EQUITY (DEFICIT) - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>0000022 - Disclosure - STOCK-BASED COMPENSATION - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATION10K</Role>
      <ShortName>STOCK-BASED COMPENSATION - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>0000023 - Disclosure - ASSET PURCHASE AGREEMENT - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ASSETPURCHASEAGREEMENT10K</Role>
      <ShortName>ASSET PURCHASE AGREEMENT - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>0000024 - Disclosure - COMMITMENTS AND CONTINGENCIES - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/COMMITMENTSANDCONTINGENCIES10K</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>0000025 - Disclosure - INCOME TAX - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/INCOMETAX10K</Role>
      <ShortName>INCOME TAX - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>0000026 - Disclosure - SUBSEQUENT EVENTS - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/SUBSEQUENTEVENTS10K</Role>
      <ShortName>SUBSEQUENT EVENTS - 10K</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>0000027 - Disclosure - ORGANIZATION AND DESCRIPTION OF BUSINESS - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ORGANIZATIONANDDESCRIPTIONOFBUSINESSQ1</Role>
      <ShortName>ORGANIZATION AND DESCRIPTION OF BUSINESS - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>0000028 - Disclosure - LIQUIDITY - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/LIQUIDITYQ1</Role>
      <ShortName>LIQUIDITY - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>0000029 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESQ1</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>0000030 - Disclosure - MERGER WITH VALLON - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/MERGERWITHVALLONQ1</Role>
      <ShortName>MERGER WITH VALLON - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>0000031 - Disclosure - FAIR VALUE MEASUREMENTS - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/FAIRVALUEMEASUREMENTSQ1</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>0000032 - Disclosure - PROPERTY AND EQUIPMENT - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/PROPERTYANDEQUIPMENTQ1</Role>
      <ShortName>PROPERTY AND EQUIPMENT - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>0000033 - Disclosure - ACCRUED EXPENSES - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ACCRUEDEXPENSESQ1</Role>
      <ShortName>ACCRUED EXPENSES - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>0000034 - Disclosure - PROMISSORY NOTES - Q1</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://gribio.com/role/PROMISSORYNOTESQ1</Role>
      <ShortName>PROMISSORY NOTES - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>0000035 - Disclosure - STOCKHOLDERS??? EQUITY - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKHOLDERSEQUITYQ1</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>0000036 - Disclosure - STOCK-BASED COMPENSATION - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATIONQ1</Role>
      <ShortName>STOCK-BASED COMPENSATION - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>0000037 - Disclosure - COMMITMENTS AND CONTINGENCIES - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/COMMITMENTSANDCONTINGENCIESQ1</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>0000038 - Disclosure - SUBSEQUENT EVENTS - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/SUBSEQUENTEVENTSQ1</Role>
      <ShortName>SUBSEQUENT EVENTS - Q1</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9954471 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies10K</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies) - 10K</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9954472 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPoliciesQ1</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies) - Q1</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9954473 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables10K</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) - 10K</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES10K</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9954474 - Disclosure - MERGER WITH VALLON (Tables) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/MERGERWITHVALLONTables10K</Role>
      <ShortName>MERGER WITH VALLON (Tables) - 10K</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/MERGERWITHVALLON10K</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9954475 - Disclosure - FAIR VALUE MEASUREMENTS (Tables) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/FAIRVALUEMEASUREMENTSTables10K</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Tables) - 10K</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/FAIRVALUEMEASUREMENTS10K</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9954476 - Disclosure - PROPERTY AND EQUIPMENT (Tables) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/PROPERTYANDEQUIPMENTTables10K</Role>
      <ShortName>PROPERTY AND EQUIPMENT (Tables) - 10K</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/PROPERTYANDEQUIPMENT10K</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9954477 - Disclosure - LEASES (Tables) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/LEASESTables10K</Role>
      <ShortName>LEASES (Tables) - 10K</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/LEASES10K</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9954478 - Disclosure - ACCRUED EXPENSES (Tables) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ACCRUEDEXPENSESTables10K</Role>
      <ShortName>ACCRUED EXPENSES (Tables) - 10K</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/ACCRUEDEXPENSES10K</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9954479 - Disclosure - STOCKHOLDERS EQUITY (DEFICIT) (Tables) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKHOLDERSEQUITYDEFICITTables10K</Role>
      <ShortName>STOCKHOLDERS EQUITY (DEFICIT) (Tables) - 10K</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/STOCKHOLDERSEQUITYDEFICIT10K</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9954480 - Disclosure - STOCK-BASED COMPENSATION (Tables) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATIONTables10K</Role>
      <ShortName>STOCK-BASED COMPENSATION (Tables) - 10K</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/STOCKBASEDCOMPENSATION10K</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9954481 - Disclosure - INCOME TAX (Tables) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/INCOMETAXTables10K</Role>
      <ShortName>INCOME TAX (Tables) - 10K</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/INCOMETAX10K</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9954482 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTablesQ1</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) - Q1</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESQ1</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9954483 - Disclosure - MERGER WITH VALLON (Tables) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/MERGERWITHVALLONTablesQ1</Role>
      <ShortName>MERGER WITH VALLON (Tables) - Q1</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/MERGERWITHVALLON10K</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9954484 - Disclosure - FAIR VALUE MEASUREMENTS (Tables) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/FAIRVALUEMEASUREMENTSTablesQ1</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Tables) - Q1</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/FAIRVALUEMEASUREMENTS10K</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9954485 - Disclosure - PROPERTY AND EQUIPMENT (Tables) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/PROPERTYANDEQUIPMENTTablesQ1</Role>
      <ShortName>PROPERTY AND EQUIPMENT (Tables) - Q1</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/PROPERTYANDEQUIPMENT10K</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9954486 - Disclosure - ACCRUED EXPENSES (Tables) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ACCRUEDEXPENSESTablesQ1</Role>
      <ShortName>ACCRUED EXPENSES (Tables) - Q1</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/ACCRUEDEXPENSES10K</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9954487 - Disclosure - STOCKHOLDERS??? EQUITY (Tables) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKHOLDERSEQUITYTablesQ1</Role>
      <ShortName>STOCKHOLDERS??? EQUITY (Tables) - Q1</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/STOCKHOLDERSEQUITYQ1</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9954488 - Disclosure - STOCK-BASED COMPENSATION (Tables) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATIONTablesQ1</Role>
      <ShortName>STOCK-BASED COMPENSATION (Tables) - Q1</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://gribio.com/role/STOCKBASEDCOMPENSATION10K</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9954489 - Disclosure - ORGANIZATION AND DESCRIPTION OF BUSINESS (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ORGANIZATIONANDDESCRIPTIONOFBUSINESSDetails10K</Role>
      <ShortName>ORGANIZATION AND DESCRIPTION OF BUSINESS (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/ORGANIZATIONANDDESCRIPTIONOFBUSINESS10K</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9954490 - Disclosure - LIQUIDITY (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/LIQUIDITYDetails10K</Role>
      <ShortName>LIQUIDITY (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/LIQUIDITY10K</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9954491 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPropertyandEquipmentDetails10K</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9954492 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Diluted Net Loss Per Common Share (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofDilutedNetLossPerCommonShareDetails10K</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Diluted Net Loss Per Common Share (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9954493 - Disclosure - MERGER WITH VALLON - Narrative (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/MERGERWITHVALLONNarrativeDetails10K</Role>
      <ShortName>MERGER WITH VALLON - Narrative (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9954494 - Disclosure - MERGER WITH VALLON - Schedule of the Net Liabilities Assumed in the Merger (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/MERGERWITHVALLONScheduleoftheNetLiabilitiesAssumedintheMergerDetails10K</Role>
      <ShortName>MERGER WITH VALLON - Schedule of the Net Liabilities Assumed in the Merger (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9954495 - Disclosure - FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/FAIRVALUEMEASUREMENTSAssetsandLiabilitiesMeasuredatFairValueDetails10K</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9954496 - Disclosure - FAIR VALUE MEASUREMENTS - Liability Measured at Estimated Fair Value (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/FAIRVALUEMEASUREMENTSLiabilityMeasuredatEstimatedFairValueDetails10K</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Liability Measured at Estimated Fair Value (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9954497 - Disclosure - FAIR VALUE MEASUREMENTS - Derivative Liability Measurement Inputs (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/FAIRVALUEMEASUREMENTSDerivativeLiabilityMeasurementInputsDetails10K</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Derivative Liability Measurement Inputs (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9954498 - Disclosure - PROPERTY AND EQUIPMENT - Schedule of Property and Equipment (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/PROPERTYANDEQUIPMENTScheduleofPropertyandEquipmentDetails10K</Role>
      <ShortName>PROPERTY AND EQUIPMENT - Schedule of Property and Equipment (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9954499 - Disclosure - PROPERTY AND EQUIPMENT - Narrative (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/PROPERTYANDEQUIPMENTNarrativeDetails10K</Role>
      <ShortName>PROPERTY AND EQUIPMENT - Narrative (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9954500 - Disclosure - LEASES - Schedule of Operating Lease Assets and Liabilities (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/LEASESScheduleofOperatingLeaseAssetsandLiabilitiesDetails10K</Role>
      <ShortName>LEASES - Schedule of Operating Lease Assets and Liabilities (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9954501 - Disclosure - LEASES - Schedule of Future Minimum Lease Payments (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/LEASESScheduleofFutureMinimumLeasePaymentsDetails10K</Role>
      <ShortName>LEASES - Schedule of Future Minimum Lease Payments (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9954502 - Disclosure - LEASES - Narrative (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/LEASESNarrativeDetails10K</Role>
      <ShortName>LEASES - Narrative (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9954503 - Disclosure - ACCRUED EXPENSES (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ACCRUEDEXPENSESDetails10K</Role>
      <ShortName>ACCRUED EXPENSES (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/ACCRUEDEXPENSESTables10K</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9954504 - Disclosure - PROMISSORY NOTES - Bridge Financing (Details) - 10K</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://gribio.com/role/PROMISSORYNOTESBridgeFinancingDetails10K</Role>
      <ShortName>PROMISSORY NOTES - Bridge Financing (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9954505 - Disclosure - PROMISSORY NOTES - TEP Note (Details) - 10K</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://gribio.com/role/PROMISSORYNOTESTEPNoteDetails10K</Role>
      <ShortName>PROMISSORY NOTES - TEP Note (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>9954506 - Disclosure - STOCKHOLDERS??? EQUITY (DEFICIT) - Narrative (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKHOLDERSEQUITYDEFICITNarrativeDetails10K</Role>
      <ShortName>STOCKHOLDERS??? EQUITY (DEFICIT) - Narrative (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/STOCKHOLDERSEQUITYTablesQ1</ParentRole>
      <Position>74</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>9954507 - Disclosure - STOCKHOLDERS EQUITY (DEFICIT) - Estimate of the Fair Value of the Warrants and Assumptions (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKHOLDERSEQUITYDEFICITEstimateoftheFairValueoftheWarrantsandAssumptionsDetails10K</Role>
      <ShortName>STOCKHOLDERS EQUITY (DEFICIT) - Estimate of the Fair Value of the Warrants and Assumptions (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/STOCKHOLDERSEQUITYDEFICITTables10K</ParentRole>
      <Position>75</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>9954508 - Disclosure - STOCKHOLDERS EQUITY (DEFICIT) - Schedule of Warrants Outstanding to Purchase Common Stock (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKHOLDERSEQUITYDEFICITScheduleofWarrantsOutstandingtoPurchaseCommonStockDetails10K</Role>
      <ShortName>STOCKHOLDERS EQUITY (DEFICIT) - Schedule of Warrants Outstanding to Purchase Common Stock (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/STOCKHOLDERSEQUITYDEFICITTables10K</ParentRole>
      <Position>76</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>9954509 - Disclosure - STOCK-BASED COMPENSATION - Narrative (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATIONNarrativeDetails10K</Role>
      <ShortName>STOCK-BASED COMPENSATION - Narrative (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>9954510 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Stock-based Compensation Expense (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATIONScheduleofStockbasedCompensationExpenseDetails10K</Role>
      <ShortName>STOCK-BASED COMPENSATION - Schedule of Stock-based Compensation Expense (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>9954511 - Disclosure - STOCK-BASED COMPENSATION - Activity of Stock Options (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATIONActivityofStockOptionsDetails10K</Role>
      <ShortName>STOCK-BASED COMPENSATION - Activity of Stock Options (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>9954512 - Disclosure - STOCK-BASED COMPENSATION - Assumptions Used to Estimate Fair Value of Options (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATIONAssumptionsUsedtoEstimateFairValueofOptionsDetails10K</Role>
      <ShortName>STOCK-BASED COMPENSATION - Assumptions Used to Estimate Fair Value of Options (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>9954513 - Disclosure - ASSET PURCHASE AGREEMENT (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ASSETPURCHASEAGREEMENTDetails10K</Role>
      <ShortName>ASSET PURCHASE AGREEMENT (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/ASSETPURCHASEAGREEMENT10K</ParentRole>
      <Position>81</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>9954514 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/COMMITMENTSANDCONTINGENCIESDetails10K</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/COMMITMENTSANDCONTINGENCIES10K</ParentRole>
      <Position>82</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>9954515 - Disclosure - INCOME TAX - Reconciliation of Federal Statutory Income Tax Rate to the Effective Income Tax Rate (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/INCOMETAXReconciliationofFederalStatutoryIncomeTaxRatetotheEffectiveIncomeTaxRateDetails10K</Role>
      <ShortName>INCOME TAX - Reconciliation of Federal Statutory Income Tax Rate to the Effective Income Tax Rate (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>9954516 - Disclosure - INCOME TAX- Components of Deferred Taxes (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/INCOMETAXComponentsofDeferredTaxesDetails10K</Role>
      <ShortName>INCOME TAX- Components of Deferred Taxes (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>9954517 - Disclosure - INCOME TAX - Narrative (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/INCOMETAXNarrativeDetails10K</Role>
      <ShortName>INCOME TAX - Narrative (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>9954518 - Disclosure - SUBSEQUENT EVENTS (Details) - 10K</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/SUBSEQUENTEVENTSDetails10K</Role>
      <ShortName>SUBSEQUENT EVENTS (Details) - 10K</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/SUBSEQUENTEVENTS10K</ParentRole>
      <Position>86</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>9954519 - Disclosure - ORGANIZATION AND DESCRIPTION OF BUSINESS (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ORGANIZATIONANDDESCRIPTIONOFBUSINESSDetailsQ1</Role>
      <ShortName>ORGANIZATION AND DESCRIPTION OF BUSINESS (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/ORGANIZATIONANDDESCRIPTIONOFBUSINESS10K</ParentRole>
      <Position>87</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>9954520 - Disclosure - LIQUIDITY (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/LIQUIDITYDetailsQ1</Role>
      <ShortName>LIQUIDITY (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/LIQUIDITY10K</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>9954521 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetailsQ1</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTablesQ1</ParentRole>
      <Position>89</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>9954522 - Disclosure - MERGER WITH VALLON - Narrative (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/MERGERWITHVALLONNarrativeDetailsQ1</Role>
      <ShortName>MERGER WITH VALLON - Narrative (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>90</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>9954523 - Disclosure - MERGER WITH VALLON - Schedule of the Net Liabilities Assumed in the Merger (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/MERGERWITHVALLONScheduleoftheNetLiabilitiesAssumedintheMergerDetailsQ1</Role>
      <ShortName>MERGER WITH VALLON - Schedule of the Net Liabilities Assumed in the Merger (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>9954524 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of Fair Value, Liabilities Measured on Recurring Basis (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/FAIRVALUEMEASUREMENTSScheduleofFairValueLiabilitiesMeasuredonRecurringBasisDetailsQ1</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Schedule of Fair Value, Liabilities Measured on Recurring Basis (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>92</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>9954525 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of Liability Measured at Estimated Fair Value (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/FAIRVALUEMEASUREMENTSScheduleofLiabilityMeasuredatEstimatedFairValueDetailsQ1</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Schedule of Liability Measured at Estimated Fair Value (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>9954526 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of Derivative Liability Measurement Inputs (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/FAIRVALUEMEASUREMENTSScheduleofDerivativeLiabilityMeasurementInputsDetailsQ1</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Schedule of Derivative Liability Measurement Inputs (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>9954527 - Disclosure - PROPERTY AND EQUIPMENT - Schedule of Property and Equipment (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/PROPERTYANDEQUIPMENTScheduleofPropertyandEquipmentDetailsQ1</Role>
      <ShortName>PROPERTY AND EQUIPMENT - Schedule of Property and Equipment (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>9954528 - Disclosure - PROPERTY AND EQUIPMENT - Narrative (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/PROPERTYANDEQUIPMENTNarrativeDetailsQ1</Role>
      <ShortName>PROPERTY AND EQUIPMENT - Narrative (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>9954529 - Disclosure - ACCRUED EXPENSES (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/ACCRUEDEXPENSESDetailsQ1</Role>
      <ShortName>ACCRUED EXPENSES (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/ACCRUEDEXPENSESTables10K</ParentRole>
      <Position>97</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>9954530 - Disclosure - PROMISSORY NOTES (Details) - Q1</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://gribio.com/role/PROMISSORYNOTESDetailsQ1</Role>
      <ShortName>PROMISSORY NOTES (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/PROMISSORYNOTES10K</ParentRole>
      <Position>98</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>9954531 - Disclosure - STOCKHOLDERS??? EQUITY - Narrative (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKHOLDERSEQUITYNarrativeDetailsQ1</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Narrative (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>9954532 - Disclosure - STOCKHOLDERS??? EQUITY - Schedule of Estimate of the Fair Value of the Warrants and Assumptions (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKHOLDERSEQUITYScheduleofEstimateoftheFairValueoftheWarrantsandAssumptionsDetailsQ1</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Schedule of Estimate of the Fair Value of the Warrants and Assumptions (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>100</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>9954533 - Disclosure - STOCKHOLDERS??? EQUITY - Schedule of Warrants Outstanding to Purchase Common Stock (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKHOLDERSEQUITYScheduleofWarrantsOutstandingtoPurchaseCommonStockDetailsQ1</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Schedule of Warrants Outstanding to Purchase Common Stock (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>101</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>9954534 - Disclosure - STOCK-BASED COMPENSATION - Narrative (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATIONNarrativeDetailsQ1</Role>
      <ShortName>STOCK-BASED COMPENSATION - Narrative (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>102</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>9954535 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Stock-based Compensation Expense (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATIONScheduleofStockbasedCompensationExpenseDetailsQ1</Role>
      <ShortName>STOCK-BASED COMPENSATION - Schedule of Stock-based Compensation Expense (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>103</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>9954536 - Disclosure - STOCK-BASED COMPENSATION - Activity of Stock Options (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/STOCKBASEDCOMPENSATIONActivityofStockOptionsDetailsQ1</Role>
      <ShortName>STOCK-BASED COMPENSATION - Activity of Stock Options (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>104</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>9954537 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/COMMITMENTSANDCONTINGENCIESDetailsQ1</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/COMMITMENTSANDCONTINGENCIES10K</ParentRole>
      <Position>105</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>9954538 - Disclosure - SUBSEQUENT EVENTS (Details) - Q1</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://gribio.com/role/SUBSEQUENTEVENTSDetailsQ1</Role>
      <ShortName>SUBSEQUENT EVENTS (Details) - Q1</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://gribio.com/role/SUBSEQUENTEVENTS10K</ParentRole>
      <Position>106</Position>
    </Report>
    <Report instance="gribio-20240626.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9999.htm</HtmlFileName>
      <LongName>Uncategorized Items - gribio-20240626.htm</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/role/uncategorizedFacts</Role>
      <ShortName>Uncategorized Items - gribio-20240626.htm</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>107</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: 9 fact(s) appearing in ix:hidden were eligible for transformation: gribio:OptionIndexedToIssuersEquityExercisableEndPeriod, us-gaap:StockholdersEquityNoteStockSplitConversionRatio1 -  gribio-20240626.htm 4</Log>
    <Log type="Warning">[rq-2602-Instant-Without-Matching-Duration] In ''FAIR VALUE MEASUREMENTS - Liability Measured at Estimated Fair Value (Details) - 10K'', fact us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue with value 0 and preferred label http://www.xbrl.org/2003/role/periodEndLabel, was not shown because there are no facts in a duration ending at 2022-12-31. Change the preferred label role or add facts.</Log>
    <Log type="Warning">[rq-2602-Instant-Without-Matching-Duration] In ''FAIR VALUE MEASUREMENTS - Liability Measured at Estimated Fair Value (Details) - 10K'', fact us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue with value 0 and preferred label http://www.xbrl.org/2003/role/periodStartLabel, was not shown because there are no facts in a duration starting at 2022-12-31. Change the preferred label role or add facts.</Log>
    <Log type="Warning">[rq-2602-Instant-Without-Matching-Duration] In ''FAIR VALUE MEASUREMENTS - Schedule of Liability Measured at Estimated Fair Value (Details) - Q1'', fact us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue with value 0 and preferred label http://www.xbrl.org/2003/role/periodEndLabel, was not shown because there are no facts in a duration ending at 2022-12-31. Change the preferred label role or add facts.</Log>
    <Log type="Warning">[rq-2602-Instant-Without-Matching-Duration] In ''FAIR VALUE MEASUREMENTS - Schedule of Liability Measured at Estimated Fair Value (Details) - Q1'', fact us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue with value 0 and preferred label http://www.xbrl.org/2003/role/periodStartLabel, was not shown because there are no facts in a duration starting at 2022-12-31. Change the preferred label role or add facts.</Log>
  </Logs>
  <InputFiles>
    <File doctype="S-1/A" isDefinitelyFs="true" isUsgaap="true" original="gribio-20240626.htm">gribio-20240626.htm</File>
    <File>gribio-20240626.xsd</File>
    <File>gribio-20240626_cal.xml</File>
    <File>gribio-20240626_def.xml</File>
    <File>gribio-20240626_lab.xml</File>
    <File>gribio-20240626_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>gribio-20240626_g1.jpg</File>
    <File>gribio-20240626_g10.jpg</File>
    <File>gribio-20240626_g11.jpg</File>
    <File>gribio-20240626_g12.jpg</File>
    <File>gribio-20240626_g13.jpg</File>
    <File>gribio-20240626_g14.jpg</File>
    <File>gribio-20240626_g15.jpg</File>
    <File>gribio-20240626_g16.jpg</File>
    <File>gribio-20240626_g17.jpg</File>
    <File>gribio-20240626_g2.jpg</File>
    <File>gribio-20240626_g3.jpg</File>
    <File>gribio-20240626_g4.jpg</File>
    <File>gribio-20240626_g5.jpg</File>
    <File>gribio-20240626_g6.jpg</File>
    <File>gribio-20240626_g7.jpg</File>
    <File>gribio-20240626_g8.jpg</File>
    <File>gribio-20240626_g9.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="865">http://fasb.org/us-gaap/2023</BaseTaxonomy>
    <BaseTaxonomy items="16">http://xbrl.sec.gov/dei/2023</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
