<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>554</ContextCount>
  <ElementCount>35</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>33</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>3</UnitCount>
  <MyReports>
    <Report instance="8ded6dd65c718ed.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>030000 - Disclosure - Form N-CSR Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/oef/role/NcsrCover</Role>
      <ShortName>Form N-CSR Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="8ded6dd65c718ed.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>030001 - Disclosure - Shareholder Report</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/oef/role/ShareholderReport</Role>
      <ShortName>Shareholder Report</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="8ded6dd65c718ed.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>040010 - Disclosure - Shareholder Report, Line Graph (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/oef/role/ShareholderReportLineGraphDetails</Role>
      <ShortName>Shareholder Report, Line Graph (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="8ded6dd65c718ed.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>040015 - Disclosure - Shareholder Report, Average Annual Return (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/oef/role/ShareholderReportAverageAnnualReturnDetails</Role>
      <ShortName>Shareholder Report, Average Annual Return (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="8ded6dd65c718ed.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>040020 - Disclosure - Shareholder Report, Holdings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/oef/role/ShareholderReportHoldingsDetails</Role>
      <ShortName>Shareholder Report, Holdings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>5</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="N-CSR" isDefinitelyNotFs="true" isNcsr="true" isOEF="true" isRRorOEF="true" isUsgaap="true" original="8ded6dd65c718ed.htm">8ded6dd65c718ed.htm</File>
    <File>cik0000104865-20260430.xsd</File>
  </InputFiles>
  <SupplementalFiles>
    <File>chartimages_1598164.jpg</File>
    <File>chartimages_1598170.jpg</File>
    <File>chartimages_1598208.jpg</File>
    <File>chartimages_1598214.jpg</File>
    <File>chartimages_1598252.jpg</File>
    <File>chartimages_1598258.jpg</File>
    <File>chartimages_1598296.jpg</File>
    <File>chartimages_1598302.jpg</File>
    <File>chartimages_1598340.jpg</File>
    <File>chartimages_1598346.jpg</File>
    <File>chartimages_1598384.jpg</File>
    <File>chartimages_1598390.jpg</File>
    <File>chartimages_1598428.jpg</File>
    <File>chartimages_1598434.jpg</File>
    <File>chartimages_1598472.jpg</File>
    <File>chartimages_1598478.jpg</File>
    <File>chartimages_1598516.jpg</File>
    <File>chartimages_1598522.jpg</File>
    <File>chartimages_1598560.jpg</File>
    <File>chartimages_1598566.jpg</File>
    <File>chartimages_1598604.jpg</File>
    <File>chartimages_1598610.jpg</File>
    <File>chartimages_1598648.jpg</File>
    <File>chartimages_1598654.jpg</File>
    <File>chartimages_1598692.jpg</File>
    <File>chartimages_1598698.jpg</File>
    <File>chartimages_1598736.jpg</File>
    <File>chartimages_1598742.jpg</File>
    <File>chartimages_1598780.jpg</File>
    <File>chartimages_1598786.jpg</File>
    <File>chartimages_1598824.jpg</File>
    <File>chartimages_1598830.jpg</File>
    <File>chartimages_1598868.jpg</File>
    <File>chartimages_1598874.jpg</File>
    <File>chartimages_1598912.jpg</File>
    <File>chartimages_1598918.jpg</File>
    <File>chartimages_1598956.jpg</File>
    <File>chartimages_1598962.jpg</File>
    <File>chartimages_1599000.jpg</File>
    <File>chartimages_1599006.jpg</File>
    <File>chartimages_1599044.jpg</File>
    <File>chartimages_1599050.jpg</File>
    <File>images_2523.jpg</File>
    <File>img07214ec01.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="42">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="27">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="1108">http://xbrl.sec.gov/oef/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>false</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
