Business Segments (Information by Operating Segment) (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Operating Revenues	$ 809,436	$ 716,982	$ 2,323,043	$ 2,102,110
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	26,127	56,310	130,203	126,676
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	42,734	16,066	75,375	72,470
Income (Loss) from Operations	(16,607)	40,244	54,828	54,206
Equity in earnings of affiliates, net	12,964	4,092	28,168	3,727
Interest Expense, Net	(9,422)	(6,357)	(22,457)	(19,307)
Non-operating pension and postretirement benefit income, net	27,561	10,489	81,564	41,028
Gain (loss) on marketable equity securities, net	14,069	59,364	176,981	(1,139)
Other Income, Net	5,218	222	27,660	11,010
Income Before Income Taxes	33,783	108,054	346,744	89,525
Depreciation of property, plant and equipment	18,741	18,481	51,886	58,098
Pension Service Cost	5,775	5,457	17,254	17,044
Identifiable Assets	3,970,533		3,970,533		$ 4,006,935
Marketable equity securities	764,831		764,831		573,102
Investments in Affiliates	171,249		171,249		155,777
Prepaid Pension Cost	1,772,859		1,772,859		1,708,305
Total Assets	6,679,472		6,679,472		6,444,119
Amortization of Intangible Assets	15,981	14,150	43,807	42,642
Impairment of goodwill and other long-lived assets	26,753	1,916	31,568	29,828
Operating Segments [Member] | Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	335,999	302,467	1,005,300	992,020
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	13,869	9,584	57,238	45,022
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	3,955	6,251	15,240	24,743
Income (Loss) from Operations	9,914	3,333	41,998	20,279
Depreciation of property, plant and equipment	8,217	6,822	23,479	24,475
Pension Service Cost	2,339	2,350	7,020	7,527
Identifiable Assets	1,975,302		1,975,302		1,975,104
Amortization of Intangible Assets	3,888	4,335	11,967	12,807
Impairment of goodwill and other long-lived assets	67	1,916	3,273	11,936
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Kaplan International [Member]
Segment Reporting Information [Line Items]
Operating Revenues	168,143	123,768	521,314	488,096
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(999)	(13,759)	23,285	21,256
Income (Loss) from Operations	(999)	(13,759)	23,285	21,256
Depreciation of property, plant and equipment	5,516	4,585	15,603	14,782
Pension Service Cost	73	102	221	334
Identifiable Assets	1,445,125		1,445,125		1,455,722
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Higher Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	85,518	83,841	239,944	243,831
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	9,525	6,853	18,152	21,883
Income (Loss) from Operations	9,525	6,853	18,152	21,883
Depreciation of property, plant and equipment	923	682	2,648	2,237
Pension Service Cost	1,109	973	3,329	3,113
Identifiable Assets	207,834		207,834		187,123
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Supplemental Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	80,489	92,568	238,055	253,641
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	11,769	19,069	33,079	12,849
Income (Loss) from Operations	11,769	19,069	33,079	12,849
Depreciation of property, plant and equipment	1,658	1,454	4,904	7,165
Pension Service Cost	954	986	2,861	3,155
Identifiable Assets	263,169		263,169		274,687
Operating Segments [Member] | Education [Member] | Kaplan Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating Revenues	3,761	3,194	10,739	9,438
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(6,426)	(2,579)	(17,375)	(10,971)
Income (Loss) from Operations	(10,381)	(8,830)	(32,615)	(35,714)
Depreciation of property, plant and equipment	120	101	324	291
Pension Service Cost	203	289	609	925
Identifiable Assets	59,174		59,174		57,572
Operating Segments [Member] | Education [Member] | Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(1,912)	(904)	(4,752)	(2,986)
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	0	0	97	5
Income (Loss) from Operations	0	0	97	5
Operating Segments [Member] | Television Broadcasting [Member]
Segment Reporting Information [Line Items]
Operating Revenues	126,498	133,828	360,089	350,038
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	41,911	54,105	113,212	116,229
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	1,361	1,360	4,081	4,081
Income (Loss) from Operations	40,550	52,745	109,131	112,148
Depreciation of property, plant and equipment	3,462	3,399	10,478	10,188
Pension Service Cost	901	817	2,692	2,449
Identifiable Assets	441,098		441,098		453,988
Operating Segments [Member] | Manufacturing [Member]
Segment Reporting Information [Line Items]
Operating Revenues	99,766	106,690	356,849	303,387
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(6,942)	11,838	27,990	30,982
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	32,541	6,987	46,138	21,112
Income (Loss) from Operations	(39,483)	4,851	(18,148)	9,870
Depreciation of property, plant and equipment	2,402	2,557	7,346	7,610
Pension Service Cost	321	318	962	1,107
Identifiable Assets	486,241		486,241		551,611
Operating Segments [Member] | Healthcare [Member]
Segment Reporting Information [Line Items]
Operating Revenues	55,445	51,426	160,184	146,601
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	6,016	8,965	23,312	23,569
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	756	823	2,317	3,440
Income (Loss) from Operations	5,260	8,142	20,995	20,129
Depreciation of property, plant and equipment	322	318	970	1,351
Pension Service Cost	141	136	421	407
Identifiable Assets	163,286		163,286		160,654
Operating Segments [Member] | Automotive [Member]
Segment Reporting Information [Line Items]
Operating Revenues	84,702	76,790	242,702	182,288
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	4,506	1,986	8,815	69
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	0	0	0	6,698
Income (Loss) from Operations	4,506	1,986	8,815	(6,629)
Depreciation of property, plant and equipment	535	619	1,555	1,735
Pension Service Cost	0	0	0	0
Identifiable Assets	160,025		160,025		151,789
Operating Segments [Member] | Other Businesses [Member]
Segment Reporting Information [Line Items]
Operating Revenues	107,539	46,306	199,477	128,953
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(19,752)	(17,429)	(57,533)	(54,864)
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	4,121	645	7,599	12,396
Income (Loss) from Operations	(23,873)	(18,074)	(65,132)	(67,260)
Depreciation of property, plant and equipment	3,649	4,589	7,578	12,211
Pension Service Cost	458	410	1,314	1,276
Identifiable Assets	660,385		660,385		365,744
Corporate Office [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0	0	0	0
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(13,481)	(12,739)	(42,831)	(34,331)
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	0	0	0	0
Income (Loss) from Operations	(13,481)	(12,739)	(42,831)	(34,331)
Depreciation of property, plant and equipment	154	177	480	528
Pension Service Cost	1,615	1,426	4,845	4,278
Identifiable Assets	84,196		84,196		$ 348,045
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	$ (513)	$ (525)	$ (1,558)	$ (1,177)