<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.2.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>224</ContextCount>
  <ElementCount>318</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>62</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="aplt-20220930x10q.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.appliedtherapeutics.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>00100 - Statement - Condensed Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/StatementCondensedBalanceSheets</Role>
      <ShortName>Condensed Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>00105 - Statement - Condensed Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/StatementCondensedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>00200 - Statement - Condensed Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/StatementCondensedStatementsOfOperations</Role>
      <ShortName>Condensed Statements of Operations</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>00300 - Statement - Condensed Statements of Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/StatementCondensedStatementsOfComprehensiveIncomeLoss</Role>
      <ShortName>Condensed Statements of Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>00400 - Statement - Condensed Statements of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/StatementCondensedStatementsOfStockholdersEquity</Role>
      <ShortName>Condensed Statements of Stockholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>00405 - Statement - Condensed Statements of Stockholders' Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/StatementCondensedStatementsOfStockholdersEquityParenthetical</Role>
      <ShortName>Condensed Statements of Stockholders' Equity (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>00500 - Statement - Condensed Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/StatementCondensedStatementsOfCashFlows</Role>
      <ShortName>Condensed Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>00505 - Statement - Condensed Statements of Cash Flows (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/StatementCondensedStatementsOfCashFlowsParenthetical</Role>
      <ShortName>Condensed Statements of Cash Flows (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>10101 - Disclosure - ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureOrganizationAndSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>10201 - Disclosure - LICENSE AGREEMENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureLicenseAgreement</Role>
      <ShortName>LICENSE AGREEMENT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>10301 - Disclosure - FAIR VALUE MEASUREMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureFairValueMeasurements</Role>
      <ShortName>FAIR VALUE MEASUREMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>10401 - Disclosure - INVESTMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureInvestments</Role>
      <ShortName>INVESTMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>10501 - Disclosure - PREPAID EXPENSES AND OTHER CURRENT ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosurePrepaidExpensesAndOtherCurrentAssets</Role>
      <ShortName>PREPAID EXPENSES AND OTHER CURRENT ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>10601 - Disclosure - ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureAccruedExpensesAndOtherCurrentLiabilities</Role>
      <ShortName>ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>10701 - Disclosure - STOCK BASED COMPENSATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockBasedCompensation</Role>
      <ShortName>STOCK BASED COMPENSATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>10801 - Disclosure - STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockholdersEquity</Role>
      <ShortName>STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>10901 - Disclosure - WARRANTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureWarrants</Role>
      <ShortName>WARRANTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>11001 - Disclosure - LEASES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureLeases</Role>
      <ShortName>LEASES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>11101 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureIncomeTaxes</Role>
      <ShortName>INCOME TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>11201 - Disclosure - BENEFIT PLANS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureBenefitPlans</Role>
      <ShortName>BENEFIT PLANS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>11301 - Disclosure - NET LOSS PER COMMON SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureNetLossPerCommonShare</Role>
      <ShortName>NET LOSS PER COMMON SHARE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>11401 - Disclosure - RELATED PARTIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureRelatedParties</Role>
      <ShortName>RELATED PARTIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>11501 - Disclosure - SUBSEQUENT EVENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureSubsequentEvents</Role>
      <ShortName>SUBSEQUENT EVENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>20102 - Disclosure - ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureOrganizationAndSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>30303 - Disclosure - FAIR VALUE MEASUREMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureFairValueMeasurementsTables</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureFairValueMeasurements</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>30403 - Disclosure - INVESTMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureInvestmentsTables</Role>
      <ShortName>INVESTMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureInvestments</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>30503 - Disclosure - PREPAID EXPENSES AND OTHER CURRENT ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosurePrepaidExpensesAndOtherCurrentAssetsTables</Role>
      <ShortName>PREPAID EXPENSES AND OTHER CURRENT ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosurePrepaidExpensesAndOtherCurrentAssets</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>30603 - Disclosure - ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesTables</Role>
      <ShortName>ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureAccruedExpensesAndOtherCurrentLiabilities</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>30703 - Disclosure - STOCK BASED COMPENSATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockBasedCompensationTables</Role>
      <ShortName>STOCK BASED COMPENSATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureStockBasedCompensation</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>30903 - Disclosure - WARRANTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureWarrantsTables</Role>
      <ShortName>WARRANTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureWarrants</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>31003 - Disclosure - LEASES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureLeasesTables</Role>
      <ShortName>LEASES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureLeases</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>31303 - Disclosure - NET LOSS PER COMMON SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureNetLossPerCommonShareTables</Role>
      <ShortName>NET LOSS PER COMMON SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureNetLossPerCommonShare</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>40101 - Disclosure - ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Stock issued (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureOrganizationAndSummaryOfSignificantAccountingPoliciesStockIssuedDetails</Role>
      <ShortName>ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Stock issued (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>40102 - Disclosure - ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Liquidity and Going Concern (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureOrganizationAndSummaryOfSignificantAccountingPoliciesLiquidityAndGoingConcernDetails</Role>
      <ShortName>ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Liquidity and Going Concern (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>40201 - Disclosure - LICENSE AGREEMENT - Columbia (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureLicenseAgreementColumbiaDetails</Role>
      <ShortName>LICENSE AGREEMENT - Columbia (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>40202 - Disclosure - LICENSE AGREEMENT - Miami University (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureLicenseAgreementMiamiUniversityDetails</Role>
      <ShortName>LICENSE AGREEMENT - Miami University (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>40301 - Disclosure - FAIR VALUE MEASUREMENTS - FV hierarchy (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureFairValueMeasurementsFvHierarchyDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - FV hierarchy (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>40302 - Disclosure - FAIR VALUE MEASUREMENTS - Transfers (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureFairValueMeasurementsTransfersDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Transfers (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>40303 - Disclosure - FAIR VALUE MEASUREMENTS - Warrants (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureFairValueMeasurementsWarrantsDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Warrants (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>40304 - Disclosure - FAIR VALUE MEASUREMENTS - Warrants Valuation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureFairValueMeasurementsWarrantsValuationDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Warrants Valuation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>40305 - Disclosure - FAIR VALUE MEASUREMENTS - Fair Values of Company's Warrant Liability (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureFairValueMeasurementsFairValuesOfCompanySWarrantLiabilityDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Fair Values of Company's Warrant Liability (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>40401 - Disclosure - INVESTMENTS - By type (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureInvestmentsByTypeDetails</Role>
      <ShortName>INVESTMENTS - By type (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>40402 - Disclosure - INVESTMENTS - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureInvestmentsAdditionalInformationDetails</Role>
      <ShortName>INVESTMENTS - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>40403 - Disclosure - INVESTMENTS - By contractual maturity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureInvestmentsByContractualMaturityDetails</Role>
      <ShortName>INVESTMENTS - By contractual maturity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>40404 - Disclosure - INVESTMENTS - Realized gains and losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureInvestmentsRealizedGainsAndLossesDetails</Role>
      <ShortName>INVESTMENTS - Realized gains and losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>40405 - Disclosure - INVESTMENTS - Unrealized losses and fair values of available-for-sale securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureInvestmentsUnrealizedLossesAndFairValuesOfAvailableForSaleSecuritiesDetails</Role>
      <ShortName>INVESTMENTS - Unrealized losses and fair values of available-for-sale securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>40501 - Disclosure - PREPAID EXPENSES AND OTHER CURRENT ASSETS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosurePrepaidExpensesAndOtherCurrentAssetsDetails</Role>
      <ShortName>PREPAID EXPENSES AND OTHER CURRENT ASSETS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosurePrepaidExpensesAndOtherCurrentAssetsTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>40601 - Disclosure - ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesDetails</Role>
      <ShortName>ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>40701 - Disclosure - STOCK BASED COMPENSATION - Plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockBasedCompensationPlansDetails</Role>
      <ShortName>STOCK BASED COMPENSATION - Plans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>40702 - Disclosure - STOCK BASED COMPENSATION - Stock-based compensation expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockBasedCompensationStockBasedCompensationExpenseDetails</Role>
      <ShortName>STOCK BASED COMPENSATION - Stock-based compensation expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>40703 - Disclosure - STOCK BASED COMPENSATION - Options (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockBasedCompensationOptionsDetails</Role>
      <ShortName>STOCK BASED COMPENSATION - Options (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>40704 - Disclosure - STOCK BASED COMPENSATION - Options activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockBasedCompensationOptionsActivityDetails</Role>
      <ShortName>STOCK BASED COMPENSATION - Options activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>40705 - Disclosure - STOCK BASED COMPENSATION - Valuation assumptions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockBasedCompensationValuationAssumptionsDetails</Role>
      <ShortName>STOCK BASED COMPENSATION - Valuation assumptions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>40706 - Disclosure - STOCK BASED COMPENSATION - RSUs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockBasedCompensationRsusDetails</Role>
      <ShortName>STOCK BASED COMPENSATION - RSUs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>40707 - Disclosure - STOCK BASED COMPENSATION - 2019 Employee Stock Purchase Plan (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockBasedCompensation2019EmployeeStockPurchasePlanDetails</Role>
      <ShortName>STOCK BASED COMPENSATION - 2019 Employee Stock Purchase Plan (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>40801 - Disclosure - STOCKHOLDERS' EQUITY - Authorized stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockholdersEquityAuthorizedStockDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Authorized stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>40802 - Disclosure - STOCKHOLDERS' EQUITY - Common Stock and Equity Distribution Agreement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockholdersEquityCommonStockAndEquityDistributionAgreementDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Common Stock and Equity Distribution Agreement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>40803 - Disclosure - STOCKHOLDERS' EQUITY - June 2022 Offering (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureStockholdersEquityJune2022OfferingDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY - June 2022 Offering (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>40901 - Disclosure - WARRANTS - Issued with Series A Preferred Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureWarrantsIssuedWithSeriesPreferredStockDetails</Role>
      <ShortName>WARRANTS - Issued with Series A Preferred Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>40902 - Disclosure - WARRANTS - Issued with the 2018 Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureWarrantsIssuedWith2018NotesDetails</Role>
      <ShortName>WARRANTS - Issued with the 2018 Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>40903 - Disclosure - WARRANTS - Issued with Series B Preferred Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureWarrantsIssuedWithSeriesBPreferredStockDetails</Role>
      <ShortName>WARRANTS - Issued with Series B Preferred Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>40904 - Disclosure - WARRANTS - Issued with June 2022 Offering (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureWarrantsIssuedWithJune2022OfferingDetails</Role>
      <ShortName>WARRANTS - Issued with June 2022 Offering (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>40905 - Disclosure - WARRANTS - Warrant Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureWarrantsWarrantActivityDetails</Role>
      <ShortName>WARRANTS - Warrant Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>41001 - Disclosure - LEASES - Lease Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureLeasesLeaseCostDetails</Role>
      <ShortName>LEASES - Lease Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>41002 - Disclosure - LEASES - Lease terms and discount rates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureLeasesLeaseTermsAndDiscountRatesDetails</Role>
      <ShortName>LEASES - Lease terms and discount rates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>41003 - Disclosure - LEASES - Maturities of Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureLeasesMaturitiesOfLeaseLiabilitiesDetails</Role>
      <ShortName>LEASES - Maturities of Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>41201 - Disclosure - BENEFIT PLANS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureBenefitPlansDetails</Role>
      <ShortName>BENEFIT PLANS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureBenefitPlans</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>41301 - Disclosure - NET LOSS PER COMMON SHARE - EPS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureNetLossPerCommonShareEpsDetails</Role>
      <ShortName>NET LOSS PER COMMON SHARE - EPS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureNetLossPerCommonShareTables</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>41302 - Disclosure - NET LOSS PER COMMON SHARE - Anti-dilutive securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureNetLossPerCommonShareAntiDilutiveSecuritiesDetails</Role>
      <ShortName>NET LOSS PER COMMON SHARE - Anti-dilutive securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>41401 - Disclosure - RELATED PARTIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureRelatedPartiesDetails</Role>
      <ShortName>RELATED PARTIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureRelatedParties</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="aplt-20220930x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>41501 - Disclosure - SUBSEQUENT EVENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.appliedtherapeutics.com/role/DisclosureSubsequentEventsDetails</Role>
      <ShortName>SUBSEQUENT EVENTS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.appliedtherapeutics.com/role/DisclosureSubsequentEvents</ParentRole>
      <Position>72</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: 29 fact(s) appearing in ix:hidden were eligible for transformation: aplt:FairValueAssetsLevel2ToLevel1TransfersAmount1, us-gaap:CommonStockSharesOutstanding, us-gaap:EarningsPerShareBasic, us-gaap:EarningsPerShareDiluted, us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic, us-gaap:NetIncomeLossAvailableToCommonStockholdersDiluted, us-gaap:PreferredStockSharesOutstanding, us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding, us-gaap:WeightedAverageNumberOfSharesOutstandingBasic -  aplt-20220930x10q.htm 9</Log>
  </Logs>
  <InputFiles>
    <File doctype="10-Q" original="aplt-20220930x10q.htm">aplt-20220930x10q.htm</File>
    <File>aplt-20220930.xsd</File>
    <File>aplt-20220930_cal.xml</File>
    <File>aplt-20220930_def.xml</File>
    <File>aplt-20220930_lab.xml</File>
    <File>aplt-20220930_pre.xml</File>
    <File>aplt-20220930xex31d1.htm</File>
    <File>aplt-20220930xex31d2.htm</File>
    <File>aplt-20220930xex32d1.htm</File>
    <File>aplt-20220930xex32d2.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="633">http://fasb.org/us-gaap/2022</BaseTaxonomy>
    <BaseTaxonomy items="31">http://xbrl.sec.gov/dei/2022</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
