Earnings Per Share (Details 2) - shares shares in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Weighted average restricted stock	28	28

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