Organization, Basis of Presentation and Recent Accounting Pronouncements (Organization and Basis of Presentation) (Narrative) (Details)	Mar. 31, 2021 televisionStation
Television Broadcasting [Member]
Number of television broadcast stations	7

Number of television broadcast stations owned by the Company.

No definition available.

Name:	ghc_NumberOfTelevisionBroadcastStationsOwned
Namespace Prefix:	ghc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant