Business Segments (Information by Operating Segment) (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Operating Revenues	$ 716,982	$ 738,820	$ 2,102,110	$ 2,168,621
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	56,310	30,212	126,676	154,811
Amortization Of Intangible Assets And Impairment of Goodwill and Other Long-Lived Assets	16,066	13,944	72,470	40,577
Income (Loss) from Operations	40,244	16,268	54,206	114,234
Equity in earnings of affiliates, net	4,092	4,683	3,727	7,829
Interest Expense, Net	(6,357)	(5,302)	(19,307)	(17,834)
Non-operating pension and postretirement benefit income, net	10,489	19,556	41,028	51,737
Gain (loss) on marketable equity securities, net	59,364	17,404	(1,139)	49,261
Other income, net	222	5,556	11,010	36,135
Income Before Income Taxes	108,054	58,165	89,525	241,362
Depreciation of property, plant and equipment	18,481	15,351	58,098	42,758
Amortization of Intangible Assets	14,150	13,572	42,642	39,512
Impairment of goodwill and other long-lived assets	1,916	372	29,828	1,065
Pension Service Cost	5,457	5,142	17,044	15,326
Identifiable Assets	3,840,661		3,840,661		$ 3,891,557
Marketable equity securities	491,172		491,172		585,080
Investments in Affiliates	157,529		157,529		162,249
Prepaid Pension Cost	1,322,151		1,322,151		1,292,350
Total Assets	5,811,513		5,811,513		5,931,236
Operating Segments [Member] | Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	302,467	357,319	992,020	1,097,536
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	9,584	(3,217)	45,022	56,320
Amortization Of Intangible Assets And Impairment of Goodwill and Other Long-Lived Assets	6,251	3,944	24,743	11,581
Income (Loss) from Operations	3,333	(7,161)	20,279	44,739
Depreciation of property, plant and equipment	6,822	6,258	24,475	18,596
Amortization of Intangible Assets	4,335	3,944	12,807	10,888
Impairment of goodwill and other long-lived assets	1,916	0	11,936	693
Pension Service Cost	2,350	2,603	7,527	7,789
Identifiable Assets	1,880,694		1,880,694		2,032,425
Operating Segments [Member] | Education [Member] | Kaplan Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating Revenues	3,194	2,450	9,438	7,121
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	(2,579)	(4,067)	(10,971)	(18,824)
Income (Loss) from Operations	(8,830)	(8,011)	(35,714)	(30,405)
Depreciation of property, plant and equipment	101	66	291	172
Pension Service Cost	289	166	925	496
Identifiable Assets	66,671		66,671		68,088
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Kaplan International [Member]
Segment Reporting Information [Line Items]
Operating Revenues	123,768	178,169	488,096	552,505
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	(13,759)	(14,226)	21,256	35,596
Income (Loss) from Operations	(13,759)	(14,226)	21,256	35,596
Depreciation of property, plant and equipment	4,585	3,600	14,782	11,198
Pension Service Cost	102	114	334	341
Identifiable Assets	1,332,098		1,332,098		1,455,122
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Higher Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	83,841	78,712	243,831	237,780
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	6,853	5,177	21,883	9,813
Income (Loss) from Operations	6,853	5,177	21,883	9,813
Depreciation of property, plant and equipment	682	840	2,237	2,066
Pension Service Cost	973	1,136	3,113	3,401
Identifiable Assets	197,983		197,983		196,761
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Test Preparation [Member]
Segment Reporting Information [Line Items]
Operating Revenues	59,737	64,710	153,687	191,533
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	13,348	4,959	(376)	8,794
Income (Loss) from Operations	13,348	4,959	(376)	8,794
Depreciation of property, plant and equipment	335	774	3,768	2,358
Pension Service Cost	748	847	2,394	2,534
Identifiable Assets	138,180		138,180		151,655
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Professional (U.S.) [Member]
Segment Reporting Information [Line Items]
Operating Revenues	32,831	33,820	99,954	110,181
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	5,721	4,939	13,225	20,943
Income (Loss) from Operations	5,721	4,939	13,225	20,943
Depreciation of property, plant and equipment	1,119	978	3,397	2,802
Pension Service Cost	238	340	761	1,017
Identifiable Assets	145,762		145,762		160,799
Operating Segments [Member] | Education [Member] | Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(904)	(542)	(2,986)	(1,584)
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	0	1	5	(2)
Income (Loss) from Operations	0	1	5	(2)
Operating Segments [Member] | Television Broadcasting [Member]
Segment Reporting Information [Line Items]
Operating Revenues	133,828	115,161	350,038	340,012
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	54,105	38,221	116,229	121,071
Amortization Of Intangible Assets And Impairment of Goodwill and Other Long-Lived Assets	1,360	1,408	4,081	4,224
Income (Loss) from Operations	52,745	36,813	112,148	116,847
Depreciation of property, plant and equipment	3,399	3,307	10,188	9,839
Pension Service Cost	817	762	2,449	2,273
Identifiable Assets	451,660		451,660		463,689
Operating Segments [Member] | Manufacturing [Member]
Segment Reporting Information [Line Items]
Operating Revenues	106,690	111,676	303,387	341,706
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	11,838	13,367	30,982	34,391
Amortization Of Intangible Assets And Impairment of Goodwill and Other Long-Lived Assets	6,987	6,522	21,112	19,580
Income (Loss) from Operations	4,851	6,845	9,870	14,811
Depreciation of property, plant and equipment	2,557	2,671	7,610	7,488
Pension Service Cost	318	20	1,107	60
Identifiable Assets	564,207		564,207		564,251
Operating Segments [Member] | Healthcare [Member]
Segment Reporting Information [Line Items]
Operating Revenues	51,426	40,688	146,601	119,057
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	8,965	3,122	23,569	10,857
Amortization Of Intangible Assets And Impairment of Goodwill and Other Long-Lived Assets	823	1,914	3,440	4,722
Income (Loss) from Operations	8,142	1,208	20,129	6,135
Depreciation of property, plant and equipment	318	566	1,351	1,783
Pension Service Cost	136	123	407	369
Identifiable Assets	160,633		160,633		160,033
Operating Segments [Member] | Other Businesses [Member]
Segment Reporting Information [Line Items]
Operating Revenues	123,096	114,200	311,241	270,618
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	(15,443)	(9,251)	(54,795)	(28,336)
Amortization Of Intangible Assets And Impairment of Goodwill and Other Long-Lived Assets	645	156	19,094	470
Income (Loss) from Operations	(16,088)	(9,407)	(73,889)	(28,806)
Depreciation of property, plant and equipment	5,208	2,330	13,946	4,351
Pension Service Cost	410	434	1,276	1,235
Identifiable Assets	524,998		524,998		567,395
Corporate Office [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0	0	0	0
Operating Income before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets.	(12,739)	(12,030)	(34,331)	(39,492)
Amortization Of Intangible Assets And Impairment of Goodwill and Other Long-Lived Assets	0	0	0	0
Income (Loss) from Operations	(12,739)	(12,030)	(34,331)	(39,492)
Depreciation of property, plant and equipment	177	219	528	701
Pension Service Cost	1,426	1,200	4,278	3,600
Identifiable Assets	258,469		258,469		$ 103,764
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	$ (525)	$ (224)	$ (1,177)	$ (308)