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Earnings Per Share (Details 2) - shares shares in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Earnings Per Share [Abstract] |  |  |  |
Weighted average restricted stock | 12 | 21 | 11 | 24

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- Definition Additional shares excluded in the calculation of diluted EPS as a result of the antidilutive effect of restricted stock using the treasury stock method. + References No definition available. + Details
Name: | ghc_AntidilutiveRestrictedStock
Namespace Prefix: | ghc_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

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