Business Segments (Information by Operating Segment) (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Operating Revenues	$ 712,455	$ 732,257
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	48,828	38,651
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	14,984	30,566
Income (Loss) from Operations	33,844	8,085
Equity in earnings (losses) of affiliates, net	13,428	(1,547)
Interest Expense, Net	(7,558)	(6,527)
Non-operating pension and postretirement benefit income, net	28,787	18,403
Gain (loss) on marketable equity securities, net	79,214	(100,393)
Other Income, Net	6,320	2,688
Income (Loss) Before Income Taxes	154,035	(79,291)
Depreciation of property, plant and equipment	16,545	16,704
Pension Service Cost	5,602	5,783
Identifiable Assets	3,918,240		$ 4,006,935
Marketable equity securities	700,352		573,102
Investments in Affiliates	169,203		155,777
Prepaid Pension Cost	1,730,625		1,708,305
Total Assets	6,518,420		6,444,119
Amortization of Intangible Assets	13,937	14,165
Impairment of goodwill and other long-lived assets	1,047	16,401
Operating Segments [Member] | Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	329,317	356,378
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	24,148	8,893
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	5,212	4,201
Income (Loss) from Operations	18,936	4,692
Depreciation of property, plant and equipment	7,780	7,329
Pension Service Cost	2,283	2,585
Identifiable Assets	1,901,257		1,975,104
Amortization of Intangible Assets	4,165	4,201
Impairment of goodwill and other long-lived assets	1,047	0
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Kaplan International [Member]
Segment Reporting Information [Line Items]
Operating Revenues	171,895	199,615
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	10,207	18,980
Income (Loss) from Operations	10,207	18,980
Depreciation of property, plant and equipment	5,252	4,578
Pension Service Cost	71	112
Identifiable Assets	1,387,772		1,455,722
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Higher Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	75,686	73,537
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	6,253	(2,020)
Income (Loss) from Operations	6,253	(2,020)
Depreciation of property, plant and equipment	852	723
Pension Service Cost	1,083	1,070
Identifiable Assets	188,602		187,123
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Supplemental Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	79,655	81,288
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	12,497	(6,550)
Income (Loss) from Operations	12,497	(6,550)
Depreciation of property, plant and equipment	1,576	1,939
Pension Service Cost	931	1,085
Identifiable Assets	265,408		274,687
Operating Segments [Member] | Education [Member] | Kaplan Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating Revenues	3,363	3,205
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(4,907)	(1,522)
Income (Loss) from Operations	(10,119)	(5,723)
Depreciation of property, plant and equipment	100	89
Pension Service Cost	198	318
Identifiable Assets	59,475		57,572
Operating Segments [Member] | Education [Member] | Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(1,282)	(1,267)
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	98	5
Income (Loss) from Operations	98	5
Operating Segments [Member] | Television Broadcasting [Member]
Segment Reporting Information [Line Items]
Operating Revenues	113,625	115,448
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	34,337	37,136
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	1,359	1,360
Income (Loss) from Operations	32,978	35,776
Depreciation of property, plant and equipment	3,473	3,343
Pension Service Cost	835	796
Identifiable Assets	450,403		453,988
Operating Segments [Member] | Manufacturing [Member]
Segment Reporting Information [Line Items]
Operating Revenues	115,960	113,458
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	15,894	13,638
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	6,987	7,137
Income (Loss) from Operations	8,907	6,501
Depreciation of property, plant and equipment	2,517	2,527
Pension Service Cost	395	394
Identifiable Assets	557,631		551,611
Operating Segments [Member] | Healthcare [Member]
Segment Reporting Information [Line Items]
Operating Revenues	50,043	45,994
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	7,921	4,479
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	781	1,310
Income (Loss) from Operations	7,140	3,169
Depreciation of property, plant and equipment	317	540
Pension Service Cost	172	159
Identifiable Assets	160,033		160,654
Operating Segments [Member] | Other Businesses [Member]
Segment Reporting Information [Line Items]
Operating Revenues	104,039	101,282
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(18,692)	(16,923)
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	645	16,558
Income (Loss) from Operations	(19,337)	(33,481)
Depreciation of property, plant and equipment	2,290	2,790
Pension Service Cost	369	463
Identifiable Assets	506,936		517,533
Corporate Office [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0	0
Income (Loss) from Operations before Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	(14,780)	(8,572)
Amortization of Intangible Assets and Impairment of Goodwill and Other Long-Lived Assets	0	0
Income (Loss) from Operations	(14,780)	(8,572)
Depreciation of property, plant and equipment	168	175
Pension Service Cost	1,548	1,386
Identifiable Assets	341,980		$ 348,045
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	$ (529)	$ (303)