Business Segments (Information by Operating Segment) (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Operating Revenues	$ 801,152	$ 652,871	$ 1,513,607	$ 1,385,128
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	55,248	31,715	104,076	70,366
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	17,657	25,838	32,641	56,404
Income (Loss) from Operations	37,591	5,877	71,435	13,962
Equity in earnings (losses) of affiliates, net	1,776	1,182	15,204	(365)
Interest Expense, Net	(5,477)	(6,423)	(13,035)	(12,950)
Non-operating pension and postretirement benefit income, net	25,216	12,136	54,003	30,539
Gain (loss) on marketable equity securities, net	83,698	39,890	162,912	(60,503)
Other Income, Net	16,122	8,100	22,442	10,788
Income (Loss) Before Income Taxes	158,926	60,762	312,961	(18,529)
Depreciation of property, plant and equipment	16,600	22,913	33,145	39,617
Pension Service Cost	5,877	5,804	11,479	11,587
Identifiable Assets	3,910,311		3,910,311		$ 4,006,935
Marketable equity securities	751,440		751,440		573,102
Investments in Affiliates	164,203		164,203		155,777
Prepaid Pension Cost	1,750,588		1,750,588		1,708,305
Total Assets	6,576,542		6,576,542		6,444,119
Amortization of Intangible Assets	13,889	14,327	27,826	28,492
Impairment of goodwill and other long-lived assets	3,768	11,511	4,815	27,912
Operating Segments [Member] | Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	339,984	333,175	669,301	689,553
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	19,221	26,545	43,369	35,438
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	6,073	14,291	11,285	18,492
Income (Loss) from Operations	13,148	12,254	32,084	16,946
Depreciation of property, plant and equipment	7,482	10,324	15,262	17,653
Pension Service Cost	2,398	2,592	4,681	5,177
Identifiable Assets	1,854,482		1,854,482		1,975,104
Amortization of Intangible Assets	3,914	4,271	8,079	8,472
Impairment of goodwill and other long-lived assets	2,159	10,020	3,206	10,020
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Kaplan International [Member]
Segment Reporting Information [Line Items]
Operating Revenues	181,276	164,713	353,171	364,328
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	14,077	16,035	24,284	35,015
Income (Loss) from Operations	14,077	16,035	24,284	35,015
Depreciation of property, plant and equipment	4,835	5,619	10,087	10,197
Pension Service Cost	77	120	148	232
Identifiable Assets	1,346,838		1,346,838		1,455,722
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Higher Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	78,740	86,453	154,426	159,990
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	2,374	17,050	8,627	15,030
Income (Loss) from Operations	2,374	17,050	8,627	15,030
Depreciation of property, plant and equipment	873	832	1,725	1,555
Pension Service Cost	1,137	1,070	2,220	2,140
Identifiable Assets	181,508		181,508		187,123
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Supplemental Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	77,911	79,785	157,566	161,073
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	8,813	330	21,310	(6,220)
Income (Loss) from Operations	8,813	330	21,310	(6,220)
Depreciation of property, plant and equipment	1,670	3,772	3,246	5,711
Pension Service Cost	976	1,084	1,907	2,169
Identifiable Assets	261,229		261,229		274,687
Operating Segments [Member] | Education [Member] | Kaplan Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating Revenues	3,615	3,039	6,978	6,244
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(6,042)	(6,870)	(10,949)	(8,392)
Income (Loss) from Operations	(12,115)	(21,161)	(22,234)	(26,884)
Depreciation of property, plant and equipment	104	101	204	190
Pension Service Cost	208	318	406	636
Identifiable Assets	64,907		64,907		57,572
Operating Segments [Member] | Education [Member] | Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(1,558)	(815)	(2,840)	(2,082)
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(1)	0	97	5
Income (Loss) from Operations	(1)	0	97	5
Operating Segments [Member] | Television Broadcasting [Member]
Segment Reporting Information [Line Items]
Operating Revenues	119,966	100,762	233,591	216,210
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	36,964	24,988	71,301	62,124
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	1,361	1,361	2,720	2,721
Income (Loss) from Operations	35,603	23,627	68,581	59,403
Depreciation of property, plant and equipment	3,543	3,446	7,016	6,789
Pension Service Cost	956	836	1,791	1,632
Identifiable Assets	446,499		446,499		453,988
Operating Segments [Member] | Manufacturing [Member]
Segment Reporting Information [Line Items]
Operating Revenues	141,123	83,239	257,083	196,697
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	19,038	5,506	34,932	19,144
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	6,610	6,988	13,597	14,125
Income (Loss) from Operations	12,428	(1,482)	21,335	5,019
Depreciation of property, plant and equipment	2,427	2,526	4,944	5,053
Pension Service Cost	246	395	641	789
Identifiable Assets	555,155		555,155		551,611
Operating Segments [Member] | Healthcare [Member]
Segment Reporting Information [Line Items]
Operating Revenues	54,696	49,181	104,739	95,175
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	9,375	10,125	17,296	14,604
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	780	1,307	1,561	2,617
Income (Loss) from Operations	8,595	8,818	15,735	11,987
Depreciation of property, plant and equipment	331	493	648	1,033
Pension Service Cost	108	112	280	271
Identifiable Assets	165,521		165,521		160,654
Operating Segments [Member] | Other Businesses [Member]
Segment Reporting Information [Line Items]
Operating Revenues	145,899	86,863	249,938	188,145
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(14,780)	(22,429)	(33,472)	(39,352)
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	2,833	1,891	3,478	18,449
Income (Loss) from Operations	(17,613)	(24,320)	(36,950)	(57,801)
Depreciation of property, plant and equipment	2,659	5,948	4,949	8,738
Pension Service Cost	487	403	856	866
Identifiable Assets	805,245		805,245		517,533
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	(14,570)	(13,020)	(29,350)	(21,592)
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	0	0	0	0
Income (Loss) from Operations	(14,570)	(13,020)	(29,350)	(21,592)
Depreciation of property, plant and equipment	158	176	326	351
Pension Service Cost	1,682	1,466	3,230	2,852
Identifiable Assets	83,409		83,409		$ 348,045
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	$ (516)	$ (349)	$ (1,045)	$ (652)