XML 58 R48.htm IDEA: XBRL DOCUMENT
v3.19.2

Investments (Investments in Marketable Equity Securities) (Details 1) - USD ($) $ in Thousands | Jun. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Investments [Abstract] |  |
Total Cost | $ 282,349 | $ 282,563
Gross unrealized gains | 235,885 | 216,111
Gross unrealized losses | (135) | (2,284)
Total Fair Value | $ 518,099 | $ 496,390

X
- Definition Amount of unrealized gain on investment on equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References No definition available. + Details
Name: | ghc_EquitySecuritiesFVNIAccumulatedGrossUnrealizedGain
Namespace Prefix: | ghc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of unrealized loss on investment on equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References No definition available. + Details
Name: | ghc_EquitySecuritiesFVNIAccumulatedGrossUnrealizedLoss
Namespace Prefix: | ghc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details
Name: | us-gaap_EquitySecuritiesFvNi
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value. + References No definition available. + Details
Name: | us-gaap_EquitySecuritiesFvNiCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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