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Revenue from Contracts with Customers (Contract Liability) (Details) - USD ($) $ in Thousands | 6 Months Ended |
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Jun. 30, 2019 | Jan. 01, 2019
Revenue from Contract with Customer [Abstract] |  |
Deferred Revenue | $ 245,729 | $ 311,214
Deferred Revenue, Period Decrease Percentage | (21.00%) |

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- Definition Deferred Revenue, Period Increase (Decrease) Percentage + References No definition available. + Details
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Namespace Prefix: | ghc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount of deferred income and obligation to transfer product and service to customer for which consideration has been received or is receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(5)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration