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Acquisitions and Dispositions of Businesses (Dispositions and Other) (Narrative) (Details) - USD ($) $ in Thousands		1 Months Ended								3 Months Ended				9 Months Ended
	Feb. 25, 2025	Oct. 31, 2026	Jul. 31, 2026	Mar. 31, 2026	Jan. 31, 2026	Dec. 31, 2025	Oct. 31, 2025	Jul. 31, 2025	Dec. 31, 2024	Sep. 30, 2026	Jun. 30, 2026	Mar. 31, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Disposal Group, Including Discontinued Operations [Line Items]
Non-operating loss on sale of business										$ 0			$ 0	$ (5,151)	$ 371
Total impairment charges										0			2,235	19,029	2,235
Impairment of goodwill														976
Noncontrolling interest, decrease from redemptions or purchase of interests												$ 16,849
Interest expense										15,769			17,164	49,171	117,547
Mandatorily redeemable noncontrolling interest, Current						$ 6,874				6,033				6,033
Kaplan Languages Group (KLG) [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Non-operating loss on sale of business											$ 5,200
Total impairment charges												19,000		19,000
Impairment of goodwill												1,000		1,000
Impairment charge related to the asset group held for sale												$ 18,000		18,000
CSI Pharmacy Holding Company, LLC
Disposal Group, Including Discontinued Operations [Line Items]
Noncontrolling interest, decrease from redemptions or purchase of interests			$ 1,900	$ 41,000				$ 1,800	$ 2,000
Clarus [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Noncontrolling interest, decrease from redemptions or purchase of interests					$ 1,000		$ 400
GHC One [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Mandatory redemption settlement amount	$ 205,000
Mandatorily redeemable noncontrolling interest, Current										6,000				6,000
Remaining GHC One and GHC Two [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Mandatory redemption settlement amount										7,300				7,300
Skin Clique \| Subsequent Event [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Noncontrolling interest, decrease from redemptions or purchase of interests		$ 18,400
Securities Subject to Mandatory Redemption [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Interest expense										$ (100)			$ 700	(1,000)	$ 68,300
Securities Subject to Mandatory Redemption [Member] \| GHC One [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Interest expense	66,200
Cash paid for CSI minority shares [Member] \| CSI Pharmacy Holding Company, LLC
Disposal Group, Including Discontinued Operations [Line Items]
Noncontrolling interest, decrease from redemptions or purchase of interests			200	16,400					600
Promissory Notes for CSI Minority Shares due 2028 [Member] \| CSI Pharmacy Holding Company, LLC
Disposal Group, Including Discontinued Operations [Line Items]
Noncontrolling interest, decrease from redemptions or purchase of interests				$ 24,600
Interest rate				8.00%								8.00%
Cash paid to settle a significant portion of the mandatorily redeemable noncontrolling interest [Member] \| GHC One [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Mandatory redemption settlement amount	186,250
GHC Class B Common Stock issued [Member] \| GHC One [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Mandatory redemption settlement amount	$ 18,750
Promissory Note for CSI minority shares due 2026 [Member] \| CSI Pharmacy Holding Company, LLC
Disposal Group, Including Discontinued Operations [Line Items]
Noncontrolling interest, decrease from redemptions or purchase of interests									$ 1,400
Interest rate									5.50%
Additional Amount Payable for CSI Minority Shares [Member] \| CSI Pharmacy Holding Company, LLC
Disposal Group, Including Discontinued Operations [Line Items]
Noncontrolling interest, decrease from redemptions or purchase of interests						$ 100
Interest rate						5.50%
Promissory Notes for CSI Minority Shares due 2030 \| CSI Pharmacy Holding Company, LLC
Disposal Group, Including Discontinued Operations [Line Items]
Noncontrolling interest, decrease from redemptions or purchase of interests			$ 1,700
Interest rate			5.50%
Education Division [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Impairment of goodwill														976
Education Division [Member] \| Kaplan Languages Group (KLG) [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Non-operating loss on sale of business											$ (5,200)
Education Division [Member] \| Kaplan International [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Impairment of goodwill												$ 1,000		$ 976
Graham Holdings Company [Member] \| CSI Pharmacy Holding Company, LLC
Disposal Group, Including Discontinued Operations [Line Items]
Ownership percentage by parent									87.50%	93.40%				93.40%
Graham Holdings Company [Member] \| Clarus [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Ownership percentage by parent							95.75%			97.50%				97.50%
Graham Holdings Company [Member] \| Skin Clique \| Subsequent Event [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Ownership percentage by parent		100.00%
Skin Clique Management, LLC \| Skin Clique \| Subsequent Event [Member]
Disposal Group, Including Discontinued Operations [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		49.00%