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Leases and Other Commitments Leases and Other Commitments (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Feb. 05, 2015
Operating Leased Assets [Line Items]        
Future minimum sublease payments due $ 94.2us-gaap_OperatingLeasesFutureMinimumPaymentsDueFutureMinimumSubleaseRentals      
Rent expense for operating leases 105.5us-gaap_LeaseAndRentalExpense 118.5us-gaap_LeaseAndRentalExpense 127.2us-gaap_LeaseAndRentalExpense  
Sublease rental income 5.4us-gaap_OperatingLeasesIncomeStatementSubleaseRevenue 5.4us-gaap_OperatingLeasesIncomeStatementSubleaseRevenue 4.4us-gaap_OperatingLeasesIncomeStatementSubleaseRevenue  
Television Broadcasting [Member]        
Operating Leased Assets [Line Items]        
Long-term programming purchase commitment 21.0us-gaap_LongTermPurchaseCommitmentAmount
/ us-gaap_StatementBusinessSegmentsAxis
= ghc_TelevisionBroadcastingMember
     
Subsequent Event [Member] | Kaplan [Member]        
Operating Leased Assets [Line Items]        
Future minimum sublease payments due       $ 61.5us-gaap_OperatingLeasesFutureMinimumPaymentsDueFutureMinimumSubleaseRentals
/ us-gaap_StatementBusinessSegmentsAxis
= ghc_KaplanMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember