<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xml:lang="en-US"
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2020-01-31"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="ghc-20210506.xsd" xlink:type="simple"/>
    <context id="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0000104889</identifier>
        </entity>
        <period>
            <startDate>2021-05-06</startDate>
            <endDate>2021-05-06</endDate>
        </period>
    </context>
    <dei:AmendmentFlag
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV80L2ZyYWc6YWY0NjNlMzQzN2FhNDkzYTgzOTNmZThmOTIwN2NjOTEvdGFibGU6NjVjMGFiYjQ0MGNkNDIzOGJiOGVkNWVlYjM5ZDg0NWYvdGFibGVyYW5nZTo2NWMwYWJiNDQwY2Q0MjM4YmI4ZWQ1ZWViMzlkODQ1Zl8xLTEtMS0xLTA_57a06282-ed1b-473d-92ac-8b37ba5233bc">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV80L2ZyYWc6YWY0NjNlMzQzN2FhNDkzYTgzOTNmZThmOTIwN2NjOTEvdGFibGU6NjVjMGFiYjQ0MGNkNDIzOGJiOGVkNWVlYjM5ZDg0NWYvdGFibGVyYW5nZTo2NWMwYWJiNDQwY2Q0MjM4YmI4ZWQ1ZWViMzlkODQ1Zl8yLTEtMS0xLTA_2e1b7076-9da5-4ce7-a855-9800970fede8">0000104889</dei:EntityCentralIndexKey>
    <dei:DocumentType
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGV4dHJlZ2lvbjo5MWY3ZTI2NjM4ODc0ZjZiYWMwZmM1MGFjODFhNTllNF8xMTE3_be78c31b-f1fe-4ad8-aa78-0b34d02020d3">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGV4dHJlZ2lvbjo5MWY3ZTI2NjM4ODc0ZjZiYWMwZmM1MGFjODFhNTllNF8yMjg_9ff3cef3-013f-4bdd-b742-a7d71775e6d0">2021-05-06</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGV4dHJlZ2lvbjo5MWY3ZTI2NjM4ODc0ZjZiYWMwZmM1MGFjODFhNTllNF8xMTE4_1aa5685f-0904-4340-b5aa-cb2a225e3b86">GRAHAM HOLDINGS CO</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6OTdhNzU5YmUzMWFhNGNlMGFhZWFjMWFjY2Y4MDNhNDYvdGFibGVyYW5nZTo5N2E3NTliZTMxYWE0Y2UwYWFlYWMxYWNjZjgwM2E0Nl8xLTAtMS0xLTA_4db79a68-2d40-415b-90dc-25ef93df2731">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6OTdhNzU5YmUzMWFhNGNlMGFhZWFjMWFjY2Y4MDNhNDYvdGFibGVyYW5nZTo5N2E3NTliZTMxYWE0Y2UwYWFlYWMxYWNjZjgwM2E0Nl8xLTUtMS0xLTA_9ac3750e-628c-4fc6-9abd-51324079fc2f">001-06714</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6OTdhNzU5YmUzMWFhNGNlMGFhZWFjMWFjY2Y4MDNhNDYvdGFibGVyYW5nZTo5N2E3NTliZTMxYWE0Y2UwYWFlYWMxYWNjZjgwM2E0Nl8xLTYtMS0xLTA_8510ec61-443e-4a10-b8d9-54425cda79d4">53-0182885</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6OTdhNzU5YmUzMWFhNGNlMGFhZWFjMWFjY2Y4MDNhNDYvdGFibGVyYW5nZTo5N2E3NTliZTMxYWE0Y2UwYWFlYWMxYWNjZjgwM2E0Nl80LTAtMS0xLTAvdGV4dHJlZ2lvbjpkNzBmYWRiNzQ3ZmI0ODFhOTdhMDQ0NWQ3YTI0ZWY3ZV81_535cb9d9-c3d1-499b-9c11-08e8a7ad363b">1300 North 17th Street</dei:EntityAddressAddressLine1>
    <dei:EntityAddressCityOrTown
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6OTdhNzU5YmUzMWFhNGNlMGFhZWFjMWFjY2Y4MDNhNDYvdGFibGVyYW5nZTo5N2E3NTliZTMxYWE0Y2UwYWFlYWMxYWNjZjgwM2E0Nl80LTAtMS0xLTAvdGV4dHJlZ2lvbjpkNzBmYWRiNzQ3ZmI0ODFhOTdhMDQ0NWQ3YTI0ZWY3ZV85_11ad8811-6c80-434c-9dc3-0dad8a5f2736">Arlington</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6OTdhNzU5YmUzMWFhNGNlMGFhZWFjMWFjY2Y4MDNhNDYvdGFibGVyYW5nZTo5N2E3NTliZTMxYWE0Y2UwYWFlYWMxYWNjZjgwM2E0Nl80LTAtMS0xLTAvdGV4dHJlZ2lvbjpkNzBmYWRiNzQ3ZmI0ODFhOTdhMDQ0NWQ3YTI0ZWY3ZV8xMw_9f96f799-f7ba-4d62-b3d1-3e61654ae4bc">VA</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6OTdhNzU5YmUzMWFhNGNlMGFhZWFjMWFjY2Y4MDNhNDYvdGFibGVyYW5nZTo5N2E3NTliZTMxYWE0Y2UwYWFlYWMxYWNjZjgwM2E0Nl80LTYtMS0xLTA_35bd387e-8cd1-482b-8863-00133e0742dd">22209</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGV4dHJlZ2lvbjo5MWY3ZTI2NjM4ODc0ZjZiYWMwZmM1MGFjODFhNTllNF8xMTE5_568e0064-f0fe-4792-ad18-27a0616225d7">703</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGV4dHJlZ2lvbjo5MWY3ZTI2NjM4ODc0ZjZiYWMwZmM1MGFjODFhNTllNF8xMTIw_9d2de859-8136-4f6b-97c3-865469e5afa4">345-6300</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6M2VlYjg3YWI0M2RmNGZlZmI5Y2NiOTFiMTE1NDE0MGEvdGFibGVyYW5nZTozZWViODdhYjQzZGY0ZmVmYjljY2I5MWIxMTU0MTQwYV8wLTAtMS0xLTA_6f487fe9-bdf9-4ad3-900f-750f246bd138">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6M2VlYjg3YWI0M2RmNGZlZmI5Y2NiOTFiMTE1NDE0MGEvdGFibGVyYW5nZTozZWViODdhYjQzZGY0ZmVmYjljY2I5MWIxMTU0MTQwYV8xLTAtMS0xLTA_e5ba9763-7018-4b70-8f1a-ec7b5556e9d3">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6M2VlYjg3YWI0M2RmNGZlZmI5Y2NiOTFiMTE1NDE0MGEvdGFibGVyYW5nZTozZWViODdhYjQzZGY0ZmVmYjljY2I5MWIxMTU0MTQwYV8yLTAtMS0xLTA_eec96b6e-3537-4e01-8d6b-ced28c216cd5">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6M2VlYjg3YWI0M2RmNGZlZmI5Y2NiOTFiMTE1NDE0MGEvdGFibGVyYW5nZTozZWViODdhYjQzZGY0ZmVmYjljY2I5MWIxMTU0MTQwYV8zLTAtMS0xLTA_7bfff60f-4ddc-4315-8f1d-46fd4778ef8e">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6ZDQ3YzdhNGIwMWE2NDNkNGEzZWQyN2Y0YTZiZGE4YzkvdGFibGVyYW5nZTpkNDdjN2E0YjAxYTY0M2Q0YTNlZDI3ZjRhNmJkYThjOV8xLTAtMS0xLTA_ac02b421-b3fb-4f8c-ac56-9a4e0699eb6c">Class&#160;B Common Stock, par value $1.00&#160;per share</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6ZDQ3YzdhNGIwMWE2NDNkNGEzZWQyN2Y0YTZiZGE4YzkvdGFibGVyYW5nZTpkNDdjN2E0YjAxYTY0M2Q0YTNlZDI3ZjRhNmJkYThjOV8xLTEtMS0xLTA_7ea3449f-0b91-4291-8e7f-c878075d8b2b">GHC</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6ZDQ3YzdhNGIwMWE2NDNkNGEzZWQyN2Y0YTZiZGE4YzkvdGFibGVyYW5nZTpkNDdjN2E0YjAxYTY0M2Q0YTNlZDI3ZjRhNmJkYThjOV8xLTItMS0xLTA_b78c9094-4773-494a-a896-f9831043458b">NYSE</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="i5d01ef47f8ea4c2e956c2d1ffcbb8ed2_D20210506-20210506"
      id="id3VybDovL2RvY3MudjEvZG9jOjhlMGRlNDNlYzE4ZDQ2NWRiMDIyN2Y5MGJhNmVmMGU1L3NlYzo4ZTBkZTQzZWMxOGQ0NjVkYjAyMjdmOTBiYTZlZjBlNV8xL2ZyYWc6OTFmN2UyNjYzODg3NGY2YmFjMGZjNTBhYzgxYTU5ZTQvdGFibGU6MzZmZTUyYzQ5NjU5NDYyM2EwNjljMzNhNDFlOTdjZjEvdGFibGVyYW5nZTozNmZlNTJjNDk2NTk0NjIzYTA2OWMzM2E0MWU5N2NmMV8wLTEtMS0xLTA_7f74bba0-2c80-444f-a278-bff0ec5f89fe">false</dei:EntityEmergingGrowthCompany>
</xbrl>
