Earnings Per Share (Details 2) - shares shares in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Weighted average restricted stock	21	29	24	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