Fair Value Measurements (Details 1) - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017
Assets
Money Market Investments		$ 157,200	$ 217,600
Marketable equity securities		452,917
Marketable equity securities			536,315
Fair Value, Measurements, Recurring [Member]
Assets
Money Market Investments	[1]	157,154	217,628
Marketable equity securities	[2]	452,917
Marketable equity securities	[2]		536,315
Other current investments	[3]	21,193	20,838
Interest Rate Swap	[4]	421
Total Financial Assets		631,685	774,781
Liabilities
Deferred compensation plan liabilities	[5]	36,573	43,414
Interest rate swap	[6]		244
Mandatorily redeemable noncontrolling interest	[7]	16,500	10,331
Total Financial Liabilities		53,073	53,989
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets
Money Market Investments	[1]	0	0
Marketable equity securities	[2]	452,917
Marketable equity securities	[2]		536,315
Other current investments	[3]	12,214	9,831
Interest Rate Swap	[4]	0
Total Financial Assets		465,131	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]	157,154	217,628
Marketable equity securities	[2]	0
Marketable equity securities	[2]		0
Other current investments	[3]	8,979	11,007
Interest Rate Swap	[4]	421
Total Financial Assets		166,554	228,635
Liabilities
Deferred compensation plan liabilities	[5]	36,573	43,414
Interest rate swap	[6]		244
Mandatorily redeemable noncontrolling interest	[7]	0	0
Total Financial Liabilities		36,573	43,658
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Assets
Money Market Investments	[1]	0	0
Marketable equity securities	[2]	0
Marketable equity securities	[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]	16,500	10,331
Total Financial Liabilities		$ 16,500	$ 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 fair value 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] As of June 30, 2018, the fair value of the mandatorily redeemable noncontrolling interest is based on the redemption value resulting from a negotiated settlement. The mandatorily redeemable noncontrolling interest was redeemed and paid in July 2018. As of December 31, 2017, 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.