<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.25.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>58</ContextCount>
  <ElementCount>28</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>8</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>1</UnitCount>
  <MyReports>
    <Report instance="d807056ddef14a.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>995100 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/dei/role/document/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="d807056ddef14a.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="d807056ddef14a.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>995447 - Disclosure - Insider Trading Policies and Procedures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc</Role>
      <ShortName>Insider Trading Policies and Procedures</ShortName>
      <MenuCategory>Notes</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="DEF 14A" isProxy="true" isUsgaap="true" original="d807056ddef14a.htm">d807056ddef14a.htm</File>
    <File>grc-20241231.xsd</File>
    <File>grc-20241231_def.xml</File>
    <File>grc-20241231_lab.xml</File>
    <File>grc-20241231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>g807056g00a02.jpg</File>
    <File>g807056g00b02.jpg</File>
    <File>g807056g01a01.jpg</File>
    <File>g807056g01a02.jpg</File>
    <File>g807056g01a03.jpg</File>
    <File>g807056g01a04.jpg</File>
    <File>g807056g01a05.jpg</File>
    <File>g807056g01a06.jpg</File>
    <File>g807056g01a07.jpg</File>
    <File>g807056g01a08.jpg</File>
    <File>g807056g01b01.jpg</File>
    <File>g807056g01b02.jpg</File>
    <File>g807056g01g09.jpg</File>
    <File>g807056g01g10.jpg</File>
    <File>g807056g02g09.jpg</File>
    <File>g807056g02g10.jpg</File>
    <File>g807056g03g09.jpg</File>
    <File>g807056g04g09.jpg</File>
    <File>g807056g05g09.jpg</File>
    <File>g807056g06g09.jpg</File>
    <File>g807056g31f09.jpg</File>
    <File>g807056g32w86.jpg</File>
    <File>g807056g46r10.jpg</File>
    <File>g807056g60a01.jpg</File>
    <File>g807056g92m30.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="5">http://fasb.org/us-gaap/2024</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/dei/2024</BaseTaxonomy>
    <BaseTaxonomy items="125">http://xbrl.sec.gov/ecd/2024</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
