Business Segments (Information by Operating Segment) (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating Revenues	$ 689,087	$ 674,766	$ 672,677	$ 659,436	$ 675,817	$ 657,225	$ 676,087	$ 582,717	$ 2,695,966	$ 2,591,846	$ 2,481,890
Income (loss) from operations	75,582	60,739	65,626	44,214	49,459	26,950	49,741	10,253	246,161	136,403	222,869
Equity in earnings (losses) of affiliates, net	1,426	9,537	931	2,579	(4,697)	(532)	1,331	649	14,473	(3,249)	(7,937)
Interest expense, net									(32,549)	(27,305)	(32,297)
Debt extinguishment costs	0	0	(11,378)	0					(11,378)	0	0
Non-operating pension and postretirement benefit income, net	53,900	22,214	23,041	21,386	17,657	17,621	18,620	18,801	120,541	72,699	80,665
Loss on marketable equity securities, net	(44,149)	44,962	(2,554)	(14,102)					(15,843)	0	0
Other income (expense), net	(12,559)	3,142	2,333	9,187	(2,640)	1,963	4,069	849	2,103	4,241	(12,642)
Income Before Income Taxes	69,138	135,070	62,735	56,565	54,860	38,244	65,899	23,786	323,508	182,789	250,658
Depreciation of property, plant and equipment	14,813	13,648	13,619	14,642	15,984	16,002	15,871	14,652	56,722	62,509	64,620
Amortization of intangible assets	13,362	$ 12,269	$ 11,399	$ 10,384	12,897	$ 10,923	$ 10,531	$ 6,836	47,414	41,187	26,671
Amortization of intangible assets and impairment of goodwill and other long-lived assets									55,523	50,801	28,274
Pension service cost									18,221	18,687	20,461
Capital Expenditures									98,067	57,080	70,712
Identifiable Assets	3,120,280				3,216,141				3,120,280	3,216,141
Marketable equity securities	496,390								496,390
Marketable equity securities					536,315					536,315
Investments in Affiliates	143,813				128,590				143,813	128,590
Prepaid Pension Cost	1,003,558				1,056,777				1,003,558	1,056,777
Total Assets	4,764,041				4,937,823				4,764,041	4,937,823
Operating Segments [Member] | Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues									1,451,015	1,516,776	1,598,461
Income (loss) from operations									97,136	77,687	95,321
Depreciation of property, plant and equipment									28,099	32,906	41,187
Amortization of intangible assets									9,362	5,162	7,516
Amortization of intangible assets and impairment of goodwill and other long-lived assets									9,362	5,162	7,516
Pension service cost									8,753	9,720	11,803
Capital Expenditures									54,159	27,520	26,497
Identifiable Assets	1,568,747				1,592,097				1,568,747	1,592,097
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Kaplan International [Member]
Segment Reporting Information [Line Items]
Operating Revenues									719,982	697,999	696,362
Income (loss) from operations									70,315	51,623	48,398
Depreciation of property, plant and equipment									15,755	14,892	17,523
Pension service cost									298	264	268
Capital Expenditures									44,469	21,667	16,252
Identifiable Assets	1,101,040				1,115,919				1,101,040	1,115,919
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Higher Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues									342,085	431,425	501,784
Income (loss) from operations									15,217	16,719	39,196
Depreciation of property, plant and equipment									4,826	9,117	13,816
Pension service cost									4,310	5,269	6,544
Capital Expenditures									4,045	2,158	3,140
Identifiable Assets	126,752				231,986				126,752	231,986
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Test Preparation [Member]
Segment Reporting Information [Line Items]
Operating Revenues									256,102	273,298	286,556
Income (loss) from operations									19,096	11,507	9,599
Depreciation of property, plant and equipment									3,941	5,286	6,287
Pension service cost									2,611	2,755	3,072
Capital Expenditures									681	1,038	4,672
Identifiable Assets	145,308				130,938				145,308	130,938
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Professional (U.S.) [Member]
Segment Reporting Information [Line Items]
Operating Revenues									134,187	115,839	115,263
Income (loss) from operations									28,608	27,558	27,436
Depreciation of property, plant and equipment									3,096	3,041	3,006
Pension service cost									1,162	913	1,076
Capital Expenditures									4,845	2,475	2,224
Identifiable Assets	166,916				91,630				166,916	91,630
Operating Segments [Member] | Education [Member] | Kaplan Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating Revenues									1,142	294	214
Income (loss) from operations									(36,064)	(29,863)	(29,279)
Depreciation of property, plant and equipment									481	570	555
Pension service cost									372	519	843
Capital Expenditures									119	182	209
Identifiable Assets	28,731				21,624				28,731	21,624
Operating Segments [Member] | Education [Member] | Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues									(2,483)	(2,079)	(1,718)
Income (loss) from operations									(36)	143	(29)
Operating Segments [Member] | Television Broadcasting [Member]
Segment Reporting Information [Line Items]
Operating Revenues									505,549	409,916	409,718
Income (loss) from operations									210,533	139,258	202,863
Depreciation of property, plant and equipment									13,204	12,179	9,942
Amortization of intangible assets and impairment of goodwill and other long-lived assets									5,632	6,349	251
Pension service cost									2,188	1,942	1,714
Capital Expenditures									27,013	16,802	27,453
Identifiable Assets	452,853				455,884				452,853	455,884
Operating Segments [Member] | Graham Healthcare Group [Member]
Segment Reporting Information [Line Items]
Operating Revenues									149,275	154,202	146,962
Income (loss) from operations									(8,401)	(2,569)	2,799
Depreciation of property, plant and equipment									2,577	4,583	2,805
Amortization of intangible assets and impairment of goodwill and other long-lived assets									14,855	7,905	6,701
Pension service cost									573	665	0
Capital Expenditures									1,741	2,987	2,954
Identifiable Assets	108,596				129,856				108,596	129,856
Operating Segments [Member] | Other Businesses [Member]
Segment Reporting Information [Line Items]
Operating Revenues									590,227	511,003	326,888
Income (loss) from operations									(246)	(19,263)	(24,901)
Depreciation of property, plant and equipment									11,835	11,723	9,570
Amortization of intangible assets and impairment of goodwill and other long-lived assets									25,674	31,385	13,806
Pension service cost									1,373	1,125	1,118
Capital Expenditures									15,154	9,771	13,093
Identifiable Assets	827,113				855,399				827,113	855,399
Corporate office [Member]
Segment Reporting Information [Line Items]
Operating Revenues									0	0	0
Income (loss) from operations									(52,861)	(58,710)	(53,213)
Depreciation of property, plant and equipment									1,007	1,118	1,116
Amortization of intangible assets and impairment of goodwill and other long-lived assets									0	0	0
Pension service cost									5,334	5,235	5,826
Capital Expenditures									0	0	715
Identifiable Assets	$ 162,971				$ 182,905				162,971	182,905
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues									$ (100)	$ (51)	$ (139)