Capital Stock, Stock Awards, and Stock Options (Earnings Per Share) (Details 5) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Earnings Per Share, Basic and Diluted, Including Two Class Method [Line Items]
Net income attributable to Graham Holdings Company common stockholders	$ 56,685	$ 125,064	$ 46,566	$ 42,891	$ 214,178	$ 24,784	$ 41,996	$ 21,086	$ 271,206	$ 302,044	$ 168,590
Less: Dividends paid–common stock outstanding and unvested restricted shares									(28,617)	(28,329)	(27,325)
Undistributed earnings									$ 242,589	$ 273,715	$ 141,265
Percent allocated to common stockholders									99.39%	99.06%	98.79%
Undistributed earnings allocated to common stockholders									$ 241,115	$ 271,150	$ 139,562
Add: Dividends paid–common stock outstanding									28,423	28,060	26,962
Numerator for basic earnings per share									269,538	299,210	166,524
Add: Additional undistributed earnings due to dilutive stock options									10	17	9
Numerator for diluted earnings per share									$ 269,548	$ 299,227	$ 166,533
Basic average number of common shares outstanding (in shares)	5,270	5,302	5,325	5,436	5,473	5,518	5,539	5,535	5,333	5,516	5,559
Denominator for diluted earnings per share (shares)									5,370	5,552	5,589
Basic net income per common share (in usd per share)	$ 10.69	$ 23.43	$ 8.69	$ 7.84	$ 38.76	$ 4.45	$ 7.51	$ 3.77	$ 50.55	$ 54.24	$ 29.95
Income Per Share From Continuing Operations To Common Stockholders [Abstract]
Earnings Per Share, Diluted (in usd per share)	$ 10.61	$ 23.28	$ 8.63	$ 7.78	$ 38.52	$ 4.42	$ 7.46	$ 3.75	$ 50.20	$ 53.89	$ 29.80
Employee Stock Option [Member]
Schedule of Earnings Per Share, Basic and Diluted, Including Two Class Method [Line Items]
Add: Effect of dilutive stock options (shares)									37	36	30