Fair Value Measurements (Details 1) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Assets
Money Market Investments		$ 111,800	$ 217,600
Total Fair Value		471,703
Total Fair Value		471,703	536,315
Fair Value, Measurements, Recurring [Member]
Assets
Money Market Investments	[1]	111,752	217,628
Total Fair Value	[2]	471,703
Total Fair Value	[2]		536,315
Other current investments	[3]	19,746	20,838
Interest Rate Swap	[4]	11
Total Financial Assets		603,212	774,781
Liabilities
Deferred compensation plan liabilities	[5]	36,373	43,414
Interest rate swap	[6]		244
Mandatorily redeemable noncontrolling interest	[7]	10,331	10,331
Total Financial Liabilities		46,704	53,989
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets
Money Market Investments	[1]	0	0
Total Fair Value	[2]	471,703
Total Fair Value	[2]		536,315
Other current investments	[3]	12,715	9,831
Interest Rate Swap	[4]	0
Total Financial Assets		484,418	546,146
Liabilities
Deferred compensation plan liabilities	[5]	0	0
Interest rate swap	[6]		0
Mandatorily redeemable noncontrolling interest	[7]	0	0
Total Financial Liabilities		0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Assets
Money Market Investments	[1]	111,752	217,628
Total Fair Value	[2]	0
Total Fair Value	[2]		0
Other current investments	[3]	7,031	11,007
Interest Rate Swap	[4]	11
Total Financial Assets		118,794	228,635
Liabilities
Deferred compensation plan liabilities	[5]	36,373	43,414
Interest rate swap	[6]		244
Mandatorily redeemable noncontrolling interest	[7]	0	0
Total Financial Liabilities		36,373	43,658
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Assets
Money Market Investments	[1]	0	0
Total Fair Value	[2]	0
Total Fair Value	[2]		0
Other current investments	[3]	0	0
Interest Rate Swap	[4]	0
Total Financial Assets		0	0
Liabilities
Deferred compensation plan liabilities	[5]	0	0
Interest rate swap	[6]		0
Mandatorily redeemable noncontrolling interest	[7]	10,331	10,331
Total Financial Liabilities		$ 10,331	$ 10,331

[1] The Company’s money market investments are included in Cash and Cash Equivalents and Restricted Cash 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. Investments in marketable securities were classified as available-for-sale in 2017 prior to the adoption of the new accounting guidance (see Note 1).

[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 valuation hierarchy.

[4] Included in Deferred Charges and Other Assets. 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] The fair value of the mandatorily redeemable noncontrolling interest is based on an EBITDA multiple, adjusted for working capital and other items, which approximates fair value.