Earnings Per Share (Details 1) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Earnings Per Share, Basic and Diluted, Including Two Class Method [Line Items]
Net income attributable to Graham Holdings Company common stockholders	$ 125,064	$ 24,784	$ 214,521	$ 87,866
Less: Dividends paid-common stock outstanding and unvested restricted shares	(7,048)	(7,047)	(28,635)	(28,329)
Undistributed earnings	$ 118,016	$ 17,737	$ 185,886	$ 59,537
Percent allocated to common stockholders	99.34%	99.07%	99.34%	99.07%
Undistributed Earnings Allocated To Common Stockholders	$ 117,235	$ 17,572	$ 184,657	$ 58,981
Add: Dividends paid-common stock outstanding	7,001	6,981	28,447	28,066
Numerator for basic earnings per share	124,236	24,553	213,104	87,047
Add: Additional undistributed earnings due to dilutive stock options	5	1	8	4
Numerator for diluted earnings per share	$ 124,241	$ 24,554	$ 213,112	$ 87,051
Weighted average shares outstanding (shares)	5,302	5,518	5,354	5,530
Denominator for diluted earnings per share (shares)	5,337	5,554	5,390	5,567
Graham Holdings Company Common Stockholders:
Basic income per common share in dollars per share	$ 23.43	$ 4.45	$ 39.81	$ 15.74
Diluted income per common share in dollars per share	$ 23.28	$ 4.42	$ 39.54	$ 15.64
Stock Option Plan [Member]
Schedule of Earnings Per Share, Basic and Diluted, Including Two Class Method [Line Items]
Add: Effect of dilutive stock options (shares)	35	36	36	37