Summary of Quarterly Operating Results and Comprehensive Income (Loss) (Unaudited) (Quarterly Impact of Certain Items) (Details 2) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Impact of Certain Items [Line Items]
Reduction to operating expenses in association with spectrum repack agreement	$ 800	$ 900	$ 6,000	$ 1,400	$ 1,400	$ 800	$ 600	$ 200	$ 9,100	$ 3,000
Earnings Per Share, Diluted, Reduction to operating expenses in association with spectrum repack agreement	$ 0.15	$ 0.16	$ 1.13	$ 0.26	$ 0.26	$ 0.14	$ 0.11	$ 0.04
Settlement Gain Related to Pension Annuity Purchase, After Tax	$ 66,900								66,900
Earnings Per Share, Diluted, Settlement gain related to pension annuity purchase	$ 12.50
Gain (Loss) on Marketable Equity Securities, after tax	$ 37,100	$ 13,100	$ 5,800	$ 18,100	$ (33,600)	$ 33,600	$ (1,900)	$ (10,700)	74,000	(12,600)
Earnings per share, diluted, gain (loss) on marketable equity securities	$ 6.92	$ 2.44	$ 1.09	$ 3.37	$ (6.28)	$ 6.26	$ (0.36)	$ (1.94)
Write-Ups of Cost Method Investments, After Tax		$ 2,800		$ 1,100					3,900
Earnings per Share, Diluted, Write-Ups of Cost Method Investments		$ 0.51		$ 0.22
Gain on Sale of Gimlet Media, After Tax				$ 21,700					21,700
Earnings per Share, Diluted, Gain on Sale of Gimlet Media				$ 4.06
Non-operating unrealized foreign currency gains (losses), after tax	$ (1,800)	$ 500	$ 100	$ 400	$ (1,200)	$ (100)	$ (1,700)	$ 100	(800)	(2,900)
Earnings Per Share, Diluted, Foreign Currency Transaction Gain (Loss), Unrealized	$ (0.33)	$ 0.09	$ 0.02	$ 0.07	$ (0.23)	$ (0.02)	$ (0.32)	$ 0.02
Effective Income Tax Rate Reconciliation, Share-Based Compensation, Excess Tax Benefit				$ 1,700				$ (1,800)	1,743	1,731	$ 6,023
Earnings Per Share, Diluted, Effective Income Tax Rate Reconciliation, Share-based Compensation Excess Tax Benefit				$ 0.32				$ 0.33
Debt extinguishment costs, after tax							$ 8,600			8,600
Earnings per share, diluted, debt extinguishment costs							$ (1.60)
Gain on Lump Sum Pension Settlement and curtailment of postretirement benefit plans, after tax					$ 22,200					22,200
Earnings per share, diluted, settlement gain related to bulk lump sum pension offering and curtailment gain					$ 4.11
Non-operating gain from sales, write-ups and impairments of investments, and related to sales of land and businesses, including losses on guarantor obligations					$ (7,700)	$ 8,000	$ 1,800	$ 3,600		5,700
Earnings per share, Diluted, non-operating gain from sales, write-ups and impairments of investments, and related to sales of businesses, including loss on guarantor obligations					$ (1.43)	$ 1.48	$ 0.34	$ 0.65
Discrete Deferred Tax Benefit						$ 17,800				17,800
Earnings per share, Diluted, nonrecurring discrete deferred state tax benefit related to the release of valuation allowances						$ 3.31
Securities Subject to Mandatory Redemption [Member]
Quarterly Impact of Certain Items [Line Items]
Interest Expense, after tax							$ 6,200			6,200
Earnings per share, diluted, interest expense							$ (1.14)
Education [Member]
Quarterly Impact of Certain Items [Line Items]
Expenses Related to Separation Inventive Plan, After Tax			$ 5,100						5,100
Earnings Per Share, Diluted, Expenses Related to Separation Incentive Plan			$ (0.95)
Education [Member] | Kaplan International [Member]
Quarterly Impact of Certain Items [Line Items]
VAT Provision, After Tax		$ 13,900							13,900
Earnings per Share, Diluted, VAT Provision		$ (2.59)
Graham Healthcare Group [Member]
Quarterly Impact of Certain Items [Line Items]
Impairment of Intangible Assets, After Tax						$ 5,800
Earnings per Share, Diluted, Impairment Of Intangible Assets						$ (1.08)
Television Broadcasting [Member]
Quarterly Impact of Certain Items [Line Items]
Impairment of Intangible Assets, After Tax	$ 6,000								$ 6,000
Earnings per Share, Diluted, Impairment Of Intangible Assets	$ (1.12)
Kaplan University Transaction [Member] | Education [Member] | Higher Education [Member]
Quarterly Impact of Certain Items [Line Items]
Gain (Loss) on Disposition of Business, Net of Tax								$ 1,800		$ 1,800
Earnings Per Share, Diluted, Gain (Loss) on Disposition of Business								$ 0.33