Capital Stock, Stock Awards, and Stock Options (Antidilutive Shares) (Details 6) - shares shares in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Capital Stock, Stock Awards, and Stock Options [Abstract]
Antidilutive Restricted Stock	12	12	23

Additional shares excluded in the calculation of diluted EPS as a result of the antidilutive effect of restricted stock using the treasury stock method.

No definition available.

Name:	ghc_AntidilutiveRestrictedStock
Namespace Prefix:	ghc_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration