<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.19.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>2</ContextCount>
  <ElementCount>10</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>2</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>4</UnitCount>
  <MyReports>
    <Report instance="jhsovbdfd-20190328.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>010001 - Document - Document And Entity Information {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://jhsovbdfd-20190328/role/DocumentDocumentandEntityInformation</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory></MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="jhsovbdfd-20190328.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>010002 - Document - John Hancock Sovereign Bond Fund - Supplement {Unlabeled}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://jhsovbdfd-20190328/role/AAAA</Role>
      <ShortName>John Hancock Sovereign Bond Fund - Supplement</ShortName>
      <MenuCategory></MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="jhsovbdfd-20190328.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>040000 - Disclosure - Risk/Return Detail Data {Elements}</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/rr/role/RiskReturnDetailData</Role>
      <ShortName>Risk/Return Detail Data</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>jhsovbdfd-20190328.xml</File>
    <File>jhsovbdfd-20190328.xsd</File>
    <File>jhsovbdfd-20190328_def.xml</File>
    <File>jhsovbdfd-20190328_lab.xml</File>
    <File>jhsovbdfd-20190328_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>xbrl1372.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2012-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/rr/2012-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
