Fair Value Measurements (Details 1) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Assets
Money market investments		$ 45,200	$ 75,500
Marketable equity securities		585,080	496,390
Fair Value, Recurring [Member]
Assets
Money market investments	[1]	45,150	75,500
Marketable equity securities	[2]	585,080	496,390
Other current investments	[3]	14,887	18,191
Interest rate swap	[4]	131	369
Total Financial Assets		645,248	590,450
Liabilities
Deferred compensation plan liabilities	[5]	34,674	36,080
Interest rate swap	[6]	1,119
Foreign exchange swap	[7]	273
Mandatorily redeemable noncontrolling interest	[8]	829
Total Financial Liabilities		36,895
Level 1 [Member] | Fair Value, Recurring [Member]
Assets
Money market investments	[1]	0	0
Marketable equity securities	[2]	585,080	496,390
Other current investments	[3]	8,843	11,203
Interest rate swap	[4]	0	0
Total Financial Assets		593,923	507,593
Liabilities
Deferred compensation plan liabilities	[5]	0	0
Interest rate swap	[6]	0
Foreign exchange swap	[7]	0
Mandatorily redeemable noncontrolling interest	[8]	0
Total Financial Liabilities		0
Level 2 [Member] | Fair Value, Recurring [Member]
Assets
Money market investments	[1]	45,150	75,500
Marketable equity securities	[2]	0	0
Other current investments	[3]	6,044	6,988
Interest rate swap	[4]	131	369
Total Financial Assets		51,325	82,857
Liabilities
Deferred compensation plan liabilities	[5]	34,674	$ 36,080
Interest rate swap	[6]	1,119
Foreign exchange swap	[7]	273
Mandatorily redeemable noncontrolling interest	[8]	0
Total Financial Liabilities		36,066
Level 3 [Member] | Fair Value, Recurring [Member]
Assets
Money market investments	[1]	0
Marketable equity securities	[2]	0
Other current investments	[3]	0
Interest rate swap	[4]	0
Total Financial Assets		0
Liabilities
Deferred compensation plan liabilities	[5]	0
Interest rate swap	[6]	0
Foreign exchange swap	[7]	0
Mandatorily redeemable noncontrolling interest	[8]	829
Total Financial Liabilities		$ 829

[1] The Company’s money market investments are included in cash and cash equivalents and the value considers the liquidity of the counterparty.

[2] The Company’s investments in marketable equity securities are held in common shares of U.S. corporations that are actively traded on U.S. stock exchanges. Price quotes for these shares are readily available.

[3] Includes U.S. Government Securities, corporate bonds, mutual funds and time deposits. These investments are valued using a market approach based on the quoted market prices of the security or inputs that include quoted market prices for similar instruments and are classified as either Level 1 or Level 2 in the fair value hierarchy.

[4] Included in Other current assets at December 31, 2019 and Deferred Charges and Other Assets at December 31, 2018. The Company utilized a market approach model using the notional amount of the interest rate swap multiplied by the observable inputs of time to maturity and market interest rates.

[5] Includes Graham Holdings Company’s Deferred Compensation Plan and supplemental savings plan benefits under the Graham Holdings Company’s Supplemental Executive Retirement Plan, which are included in accrued compensation and related benefits. These plans measure the market value of a participant’s balance in a notional investment account that is comprised primarily of mutual funds, which are based on observable market prices. However, since the deferred compensation obligations are not exchanged in an active market, they are classified as Level 2 in the fair value hierarchy. Realized and unrealized gains (losses) on deferred compensation are included in operating income.

[6] Included in Other Liabilities. The Company utilized a market approach model using the notional amount of the interest rate swap multiplied by the observable inputs of time to maturity and market interest rates.

[7] Included in Accounts payable and accrued liabilities, and valued based on a valuation model that calculates the differential between the contract price and the market-based forward rate.

[8] The fair value of the mandatorily redeemable noncontrolling interest is based on the fair value of the underlying subsidiaries owned by GHC One (see Note 3), after taking into account any debt and other noncontrolling interests of its subsidiary investments. The fair value of the owned subsidiaries is determined by reference to either a discounted cash flow or EBITDA multiple, which approximates fair value.