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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Earnings Per Share, Basic and Diluted, Including Two Class Method [Line Items]
Net income attributable to Graham Holdings Company common stockholders	$ 145,881	$ 43,145	$ 57,081	$ 81,748	$ 56,685	$ 125,064	$ 46,566	$ 42,891	$ 327,855	$ 271,206	$ 302,044
Less: Dividends paid–common stock outstanding and unvested restricted shares									(29,553)	(28,617)	(28,329)
Undistributed earnings									$ 298,302	$ 242,589	$ 273,715
Percent allocated to common stockholders									99.45%	99.39%	99.06%
Undistributed earnings allocated to common stockholders									$ 296,665	$ 241,115	$ 271,150
Add: Dividends paid–common stock outstanding									29,387	28,423	28,060
Numerator for basic earnings per share									326,052	269,538	299,210
Add: Additional undistributed earnings due to dilutive stock options									13	10	17
Numerator for diluted earnings per share									$ 326,065	$ 269,548	$ 299,227
Basic average number of common shares outstanding (in shares)	5,284	5,285	5,285	5,284	5,270	5,302	5,325	5,436	5,285	5,333	5,516
Denominator for diluted earnings per share (shares)									5,327	5,370	5,552
Basic net income per common share (in usd per share)	$ 27.45	$ 8.12	$ 10.74	$ 15.38	$ 10.69	$ 23.43	$ 8.69	$ 7.84	$ 61.70	$ 50.55	$ 54.24
Income Per Share From Continuing Operations To Common Stockholders [Abstract]
Earnings Per Share, Diluted (in usd per share)	$ 27.25	$ 8.05	$ 10.65	$ 15.26	$ 10.61	$ 23.28	$ 8.63	$ 7.78	$ 61.21	$ 50.20	$ 53.89
Share-based Payment Arrangement, Option [Member]
Schedule of Earnings Per Share, Basic and Diluted, Including Two Class Method [Line Items]
Add: Effect of dilutive stock options (shares)									42	37	36