Business Segments (Information by Operating Segment) (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Operating Revenues	$ 763,478	$ 738,820	$ 737,602	$ 692,199	$ 689,087	$ 674,766	$ 672,677	$ 659,436	$ 2,932,099	$ 2,695,966	$ 2,591,846
Income (loss) from operations	30,312	16,268	57,963	40,003	75,582	60,739	65,626	44,214	144,546	246,161	136,403
Equity in earnings (losses) of affiliates, net	3,835	4,683	1,467	1,679	1,426	9,537	931	2,579	11,664	14,473	(3,249)
Interest expense, net									(23,628)	(32,549)	(27,305)
Debt extinguishment costs					0	0	(11,378)	0	0	(11,378)	0
Non-operating pension and postretirement benefit income, net	111,061	19,556	12,253	19,928	53,900	22,214	23,041	21,386	162,798	120,541	72,699
Gain (loss) on marketable equity securities, net	49,407	17,404	7,791	24,066	(44,149)	44,962	(2,554)	(14,102)	98,668	(15,843)	0
Other income, net	(3,704)	5,556	1,228	29,351	(12,559)	3,142	2,333	9,187	32,431	2,103	4,241
Income Before Income Taxes	185,117	58,165	73,895	109,302	69,138	135,070	62,735	56,565	426,479	323,508	182,789
Depreciation of property, plant and equipment	16,495	15,351	13,884	13,523	14,813	13,648	13,619	14,642	59,253	56,722	62,509
Amortization of intangible assets and impairment of goodwill and other long-lived assets									62,395	55,523	50,801
Amortization of Intangible Assets	13,731	13,572	12,880	13,060	13,362	12,269	11,399	10,384	53,243	47,414	41,187
Impairment of Long-Lived Assets	8,087	$ 372	$ 693	$ 0	0	$ 8,109	$ 0	$ 0	9,152	8,109	9,614
Pension service cost									20,422	18,221	18,687
Capital Expenditures									93,947	98,067	57,080
Identifiable Assets	3,891,557				3,120,280				3,891,557	3,120,280
Marketable equity securities	585,080				496,390				585,080	496,390
Investments in Affiliates	162,249				143,813				162,249	143,813
Prepaid Pension Cost	1,292,350				1,003,558				1,292,350	1,003,558
Total Assets	5,931,236				4,764,041				5,931,236	4,764,041
Operating Segments [Member] | Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues									1,451,750	1,451,015	1,516,776
Income (loss) from operations									48,072	97,136	77,687
Depreciation of property, plant and equipment									25,655	28,099	32,906
Amortization of intangible assets and impairment of goodwill and other long-lived assets									15,608	9,362	5,162
Amortization of Intangible Assets									14,915	9,362	5,162
Impairment of Long-Lived Assets									693	0	0
Pension service cost									10,385	8,753	9,720
Capital Expenditures									57,246	54,159	27,520
Identifiable Assets	2,032,425				1,568,747				2,032,425	1,568,747
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Kaplan International [Member]
Segment Reporting Information [Line Items]
Operating Revenues									750,245	719,982	697,999
Income (loss) from operations									42,129	70,315	51,623
Depreciation of property, plant and equipment									15,394	15,755	14,892
Pension service cost									454	298	264
Capital Expenditures									48,362	44,469	21,667
Identifiable Assets	1,455,122				1,101,040				1,455,122	1,101,040
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Higher Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues									305,672	342,085	431,425
Income (loss) from operations									13,960	15,217	16,719
Depreciation of property, plant and equipment									2,883	4,826	9,117
Pension service cost									4,535	4,310	5,269
Capital Expenditures									3,463	4,045	2,158
Identifiable Assets	196,761				126,752				196,761	126,752
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Test Preparation [Member]
Segment Reporting Information [Line Items]
Operating Revenues									243,917	256,102	273,298
Income (loss) from operations									7,399	19,096	11,507
Depreciation of property, plant and equipment									3,284	3,941	5,286
Pension service cost									3,378	2,611	2,755
Capital Expenditures									1,527	681	1,038
Identifiable Assets	151,655				145,308				151,655	145,308
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Professional (U.S.) [Member]
Segment Reporting Information [Line Items]
Operating Revenues									144,897	134,187	115,839
Income (loss) from operations									27,088	28,608	27,558
Depreciation of property, plant and equipment									3,848	3,096	3,041
Pension service cost									1,356	1,162	913
Capital Expenditures									3,835	4,845	2,475
Identifiable Assets	160,799				166,916				160,799	166,916
Operating Segments [Member] | Education [Member] | Kaplan Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating Revenues									9,480	1,142	294
Income (loss) from operations									(42,499)	(36,064)	(29,863)
Depreciation of property, plant and equipment									246	481	570
Pension service cost									662	372	519
Capital Expenditures									59	119	182
Identifiable Assets	68,088				28,731				68,088	28,731
Operating Segments [Member] | Education [Member] | Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues									(2,461)	(2,483)	(2,079)
Income (loss) from operations									(5)	(36)	143
Operating Segments [Member] | Television Broadcasting [Member]
Segment Reporting Information [Line Items]
Operating Revenues									463,464	505,549	409,916
Income (loss) from operations									152,668	210,533	139,258
Depreciation of property, plant and equipment									12,817	13,204	12,179
Amortization of intangible assets and impairment of goodwill and other long-lived assets									13,408	5,632	6,349
Pension service cost									3,025	2,188	1,942
Capital Expenditures									19,362	27,013	16,802
Identifiable Assets	463,689				452,853				463,689	452,853
Operating Segments [Member] | Manufacturing [Member]
Segment Reporting Information [Line Items]
Operating Revenues									449,053	487,619	414,193
Income (loss) from operations									20,467	28,851	14,947
Depreciation of property, plant and equipment									10,036	9,515	9,173
Amortization of intangible assets and impairment of goodwill and other long-lived assets									26,342	24,746	31,052
Pension service cost									80	72	79
Capital Expenditures									11,218	14,806	8,012
Identifiable Assets	564,251				593,111				564,251	593,111
Operating Segments [Member] | Graham Healthcare Group [Member]
Segment Reporting Information [Line Items]
Operating Revenues									161,768	149,275	154,202
Income (loss) from operations									7,908	(8,401)	(2,569)
Depreciation of property, plant and equipment									2,314	2,577	4,583
Amortization of intangible assets and impairment of goodwill and other long-lived assets									6,411	14,855	7,905
Pension service cost									492	573	665
Capital Expenditures									2,303	1,741	2,987
Identifiable Assets	160,033				108,596				160,033	108,596
Operating Segments [Member] | SocialCode [Member]
Segment Reporting Information [Line Items]
Operating Revenues									62,754	58,728	62,077
Income (loss) from operations									(3,283)	(1,081)	(3,674)
Depreciation of property, plant and equipment									1,017	797	1,004
Amortization of intangible assets and impairment of goodwill and other long-lived assets									626	928	333
Pension service cost									877	723	593
Capital Expenditures									643	113	756
Identifiable Assets	221,746				213,394				221,746	213,394
Operating Segments [Member] | Other Businesses [Member]
Segment Reporting Information [Line Items]
Operating Revenues									344,092	43,880	34,733
Income (loss) from operations									(30,129)	(28,016)	(30,536)
Depreciation of property, plant and equipment									6,539	1,523	1,546
Amortization of intangible assets and impairment of goodwill and other long-lived assets									0	0	0
Pension service cost									763	578	453
Capital Expenditures									3,060	235	1,003
Identifiable Assets	345,649				20,608				345,649	20,608
Corporate office [Member]
Segment Reporting Information [Line Items]
Operating Revenues									0	0	0
Income (loss) from operations									(51,157)	(52,861)	(58,710)
Depreciation of property, plant and equipment									875	1,007	1,118
Amortization of intangible assets and impairment of goodwill and other long-lived assets									0	0	0
Pension service cost									4,800	5,334	5,235
Capital Expenditures									115	0	0
Identifiable Assets	$ 103,764				$ 162,971				103,764	162,971
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues									$ (782)	$ (100)	$ (51)