Business Segments (Information by Operating Segment) (Details 1) - USD ($) $ in Thousands	3 Months Ended							9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Operating Revenues	$ 738,820	$ 737,602	$ 692,199	$ 689,087	$ 674,766	$ 672,677	$ 659,436	$ 2,168,621	$ 2,006,879	$ 2,695,966	$ 2,591,846
Income (Loss) from Operations	16,268	57,963	40,003	75,582	60,739	65,626	44,214	114,234	170,579	246,161	136,403
Equity in earnings of affiliates, net	4,683	1,467	1,679	1,426	9,537	931	2,579	7,829	13,047	14,473	(3,249)
Interest Expense, Net	(5,302)	(6,807)	(5,725)	(5,062)	(5,524)	(15,264)	(6,699)	(17,834)	(27,487)	(32,549)	(27,305)
Debt Extinguishment Costs	0			0	0	(11,378)	0	0	(11,378)	(11,378)	0
Non-operating pension and postretirement benefit income, net	19,556	12,253	19,928	53,900	22,214	23,041	21,386	51,737	66,641	120,541	72,699
Gain on marketable equity securities, net	17,404	7,791	24,066	(44,149)	44,962	(2,554)	(14,102)	49,261	28,306	(15,843)	0
Other income, net	5,556	1,228	29,351	(12,559)	3,142	2,333	9,187	36,135	14,662	2,103	4,241
Income Before Income Taxes	58,165	73,895	109,302	69,138	135,070	62,735	56,565	241,362	254,370	323,508	182,789
Depreciation of property, plant and equipment	15,351	13,884	13,523	14,813	13,648	13,619	14,642	42,758	41,909	56,722	62,509
Amortization Of Intangible Assets and Impairment of Long-Lived Assets	13,944	13,573	13,060	13,362	20,378	11,399	10,384	40,577	42,161	55,523	50,801
Amortization of Intangible Assets	13,572				12,269			39,512	34,052
Impairment of long-lived assets	372				8,109			1,065	8,109
Pension Service Cost	5,142	4,963	5,221	4,491	4,473	4,317	4,940	15,326	13,730	18,221	18,687
Capital Expenditures										98,067	57,080
Identifiable Assets	3,749,520			3,120,280				3,749,520		3,120,280
Marketable equity securities	535,564			496,390				535,564		496,390
Investments in Affiliates	163,986			143,813				163,986		143,813
Prepaid Pension Cost	1,038,676			1,003,558				1,038,676		1,003,558
Total Assets	5,487,746			4,764,041				5,487,746		4,764,041
Operating Segments [Member] | Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	357,319	367,763	372,454	346,910	358,601	370,005	375,499	1,097,536	1,104,105	1,451,015	1,516,776
Income (Loss) from Operations	(7,161)	26,305	25,595	14,620	22,262	37,554	22,700	44,739	82,516	97,136	77,687
Depreciation of property, plant and equipment	6,258	6,137	6,201	6,969	6,685	6,839	7,606	18,596	21,130	28,099	32,906
Amortization Of Intangible Assets and Impairment of Long-Lived Assets	3,944	4,070	3,567	3,868	2,682	1,663	1,149	11,581	5,494	9,362	5,162
Amortization of Intangible Assets	3,944				2,682			10,888	5,494
Impairment of long-lived assets	0				0			693	0
Pension Service Cost	2,603	2,522	2,664	2,104	2,107	1,878	2,664	7,789	6,649	8,753	9,720
Capital Expenditures										54,159	27,520
Identifiable Assets	1,925,819			1,568,747				1,925,819		1,568,747
Operating Segments [Member] | Education [Member] | Kaplan Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating Revenues	2,450				143			7,121	870
Income (Loss) from Operations	(8,011)				(9,452)			(30,405)	(27,110)
Depreciation of property, plant and equipment	66				119			172	431
Pension Service Cost	166				123			496	250
Identifiable Assets	66,989			28,731				66,989		28,731
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Kaplan International [Member]
Segment Reporting Information [Line Items]
Operating Revenues	178,169				167,668			552,505	535,553
Income (Loss) from Operations	(14,226)				8,375			35,596	52,966
Depreciation of property, plant and equipment	3,600				3,759			11,198	11,497
Pension Service Cost	114				66			341	233
Identifiable Assets	1,336,238			1,101,040				1,336,238		1,101,040
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Higher Education [Member]
Segment Reporting Information [Line Items]
Operating Revenues	78,712				89,269			237,780	275,080
Income (Loss) from Operations	5,177				6,042			9,813	18,616
Depreciation of property, plant and equipment	840				915			2,066	4,047
Pension Service Cost	1,136				1,050			3,401	3,260
Identifiable Assets	202,553			126,752				202,553		126,752
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Test Preparation [Member]
Segment Reporting Information [Line Items]
Operating Revenues	64,710				67,749			191,533	195,504
Income (Loss) from Operations	4,959				10,572			8,794	17,213
Depreciation of property, plant and equipment	774				1,033			2,358	2,984
Pension Service Cost	847				577			2,534	2,035
Identifiable Assets	165,471			145,308				165,471		145,308
Operating Segments [Member] | Education [Member] | Reportable Subsegments [Member] | Professional (U.S.) [Member]
Segment Reporting Information [Line Items]
Operating Revenues	33,820				34,302			110,181	98,715
Income (Loss) from Operations	4,939				6,768			20,943	20,863
Depreciation of property, plant and equipment	978				859			2,802	2,171
Pension Service Cost	340				291			1,017	871
Identifiable Assets	154,568			166,916				154,568		166,916
Operating Segments [Member] | Education [Member] | Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(542)				(530)			(1,584)	(1,617)
Income (Loss) from Operations	1				(43)			(2)	(32)
Operating Segments [Member] | Television Broadcasting [Member]
Segment Reporting Information [Line Items]
Operating Revenues	115,161	116,628	108,223	152,647	130,014	114,086	108,802	340,012	352,902	505,549	409,916
Income (Loss) from Operations	36,813	44,494	35,540	73,420	55,453	41,118	40,542	116,847	137,113	210,533	139,258
Depreciation of property, plant and equipment	3,307	3,293	3,239	3,961	3,198	2,974	3,071	9,839	9,243	13,204	12,179
Amortization Of Intangible Assets and Impairment of Long-Lived Assets	1,408	1,408	1,408	1,408	1,408	1,408	1,408	4,224	4,224	5,632	6,349
Pension Service Cost	762	780	731	550	544	601	493	2,273	1,638	2,188	1,942
Capital Expenditures										27,013	16,802
Identifiable Assets	470,915			452,853				470,915		452,853
Operating Segments [Member] | Manufacturing [Member]
Segment Reporting Information [Line Items]
Operating Revenues	111,676	114,873	115,157	117,723	126,028	126,462	117,406	341,706	369,896	487,619	414,193
Income (Loss) from Operations	6,845	4,692	3,274	6,412	5,146	8,665	8,628	14,811	22,439	28,851	14,947
Depreciation of property, plant and equipment	2,671	2,384	2,433	2,400	2,333	2,331	2,451	7,488	7,115	9,515	9,173
Amortization Of Intangible Assets and Impairment of Long-Lived Assets	6,522	6,528	6,530	6,530	6,345	5,935	5,936	19,580	18,216	24,746	31,052
Pension Service Cost	20	15	25	18	18	19	17	60	54	72	79
Capital Expenditures										14,806	8,012
Identifiable Assets	577,244			593,111				577,244		593,111
Operating Segments [Member] | Healthcare [Member]
Segment Reporting Information [Line Items]
Operating Revenues	40,688	40,641	37,728	37,960	35,486	38,208	37,621	119,057	111,315	149,275	154,202
Income (Loss) from Operations	1,208	2,598	2,329	928	(8,702)	764	(1,391)	6,135	(9,329)	(8,401)	(2,569)
Depreciation of property, plant and equipment	566	607	610	629	648	647	653	1,783	1,948	2,577	4,583
Amortization Of Intangible Assets and Impairment of Long-Lived Assets	1,914	1,410	1,398	1,399	9,839	1,809	1,808	4,722	13,456	14,855	7,905
Pension Service Cost	123	63	183	143	143	165	122	369	430	573	665
Capital Expenditures										1,741	2,987
Identifiable Assets	132,068			108,596				132,068		108,596
Operating Segments [Member] | SocialCode [Member]
Segment Reporting Information [Line Items]
Operating Revenues	15,975	16,382	13,447	16,878	13,781	14,770	13,299	45,804	41,850	58,728	62,077
Income (Loss) from Operations	(378)	(975)	(4,018)	(682)	5,124	(1,742)	(3,781)	(5,371)	(399)	(1,081)	(3,674)
Depreciation of property, plant and equipment	356	384	152	177	187	200	233	892	620	797	1,004
Amortization Of Intangible Assets and Impairment of Long-Lived Assets	156	157	157	157	104	584	83	470	771	928	333
Pension Service Cost	219	191	248	181	181	205	156	658	542	723	593
Capital Expenditures										113	756
Identifiable Assets	238,253			213,394				238,253		213,394
Operating Segments [Member] | Other Businesses [Member]
Segment Reporting Information [Line Items]
Operating Revenues	98,225	81,359	45,230	17,024	10,856	9,167	6,833	224,814	26,856	43,880	34,733
Income (Loss) from Operations	(9,029)	(5,913)	(8,493)	(5,840)	(5,657)	(7,977)	(8,542)	(23,435)	(22,176)	(28,016)	(30,536)
Depreciation of property, plant and equipment	1,974	837	648	428	345	375	375	3,459	1,095	1,523	1,546
Amortization Of Intangible Assets and Impairment of Long-Lived Assets	0	0	0	0	0	0	0	0	0	0	0
Pension Service Cost	215	161	201	161	147	154	116	577	417	578	453
Capital Expenditures										235	1,003
Identifiable Assets	333,720			20,608				333,720		20,608
Corporate Office [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0	0	0	0	0	0	0	0	0	0	0
Income (Loss) from Operations	(12,030)	(13,238)	(14,224)	(13,276)	(12,887)	(12,756)	(13,942)	(39,492)	(39,585)	(52,861)	(58,710)
Depreciation of property, plant and equipment	219	242	240	249	252	253	253	701	758	1,007	1,118
Amortization Of Intangible Assets and Impairment of Long-Lived Assets	0	0	0	0	0	0	0	0	0	0	0
Pension Service Cost	1,200	1,231	1,169	1,334	1,333	1,295	1,372	3,600	4,000	5,334	5,235
Capital Expenditures										0	0
Identifiable Assets	71,501			162,971				71,501		162,971
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	$ (224)	$ (44)	$ (40)	$ (55)	$ 0	$ (21)	$ (24)	$ (308)	$ (45)	$ (100)	$ (51)