Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Feb. 20, 2019	Jun. 29, 2018
Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Period Focus	FY
Trading Symbol	ghc
Entity Registrant Name	GRAHAM HOLDINGS CO
Entity Central Index Key	0000104889
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
Entity Public Float			$ 2,500
Class A Common Stock [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		964,001
Class B Common Stock [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		4,353,623