<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>16</ContextCount>
  <ElementCount>77</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>15</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>2</UnitCount>
  <MyReports>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>01001 - Document - Document and Entity Information {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://troweprice.com/20211231/role/DocumentAndEntityInformation1</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory></MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>true</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>01002 - Document - Risk/Return Summary (T. Rowe Price New Horizons Fund, Inc.) {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://troweprice.com/20211231/role/RRSummary2</Role>
      <ShortName>Risk/Return Summary (T. Rowe Price New Horizons Fund, Inc.)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="c485bpos.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>01003 - Disclosure - Risk/Return Detail Data (T. Rowe Price New Horizons Fund, Inc.) {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://troweprice.com/20211231/role/RRDetailData3</Role>
      <ShortName>Risk/Return Detail Data (T. Rowe Price New Horizons Fund, Inc.)</ShortName>
      <MenuCategory></MenuCategory>
      <Position>3</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="485BPOS" original="c485bpos.htm">c485bpos.htm</File>
    <File>c485bpos-20220428.xsd</File>
    <File>c485bpos-20220428_cal.xml</File>
    <File>c485bpos-20220428_def.xml</File>
    <File>c485bpos-20220428_lab.xml</File>
    <File>c485bpos-20220428_pre.xml</File>
    <File>ex99gcustagreemt-cust1.htm</File>
    <File>ex99gcustagreemt-cust2.htm</File>
    <File>ex99hothmatcont-ela1.htm</File>
    <File>ex99hothmatcont-fa1.htm</File>
    <File>ex99hothmatcont-fa2.htm</File>
    <File>ex99hothmatcont-fa3.htm</File>
    <File>ex99hothmatcont-h10520.htm</File>
    <File>ex99hothmatcont-h1421.htm</File>
    <File>ex99hothmatcont-rps1.htm</File>
    <File>ex99hothmatcont-trsf1.htm</File>
    <File>ex99jotheropinin-opin1.htm</File>
    <File>ex99jotheropinin-poa.htm</File>
    <File>ex99jotheropinin-pwc.htm</File>
    <File>ex99pcodeeth-code.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>img_23bddcaf78c94f2.jpg</File>
    <File>img_2a47af9da3614f1.jpg</File>
    <File>img_4762b2505cdd4f2.jpg</File>
    <File>img_6d283c3d86c34f1.jpg</File>
    <File>img_9fef6b15bcbf4f2.jpg</File>
    <File>img_d111440356364f3.jpg</File>
    <File>img_d8252dfaa4144f3.jpg</File>
    <File>img_d8bd0e434de94f2.jpg</File>
    <File>img_f5c7265e024b4f2.jpg</File>
    <File>BarChart1.png</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="8">http://xbrl.sec.gov/dei/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy items="119">http://xbrl.sec.gov/rr/2018-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
