Capital Stock, Stock Awards, and Stock Options (Antidilutive Shares) (Details 6) - shares shares in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Shares [Abstract]
Antidilutive Restricted Stock	30	40	52
Antidilutive Options	0	0	39

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