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Pension and Postretirement Plans (Key Assumptions - Obligation) (Details 3) (Benefit Obligation [Member])
Dec. 31, 2014
Dec. 31, 2013
Pension Plans [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Discount rate 4.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ ghc_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAssumptionAxis
= ghc_BenefitObligationMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		 4.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ ghc_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAssumptionAxis
= ghc_BenefitObligationMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Rate of compensation increase 4.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ ghc_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAssumptionAxis
= ghc_BenefitObligationMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		 4.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ ghc_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAssumptionAxis
= ghc_BenefitObligationMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Supplemental Executive Retirement Plan (SERP) [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Discount rate 4.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ ghc_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAssumptionAxis
= ghc_BenefitObligationMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember		 4.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ ghc_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAssumptionAxis
= ghc_BenefitObligationMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember
Rate of compensation increase 4.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ ghc_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAssumptionAxis
= ghc_BenefitObligationMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember		 4.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ ghc_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAssumptionAxis
= ghc_BenefitObligationMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember