Goodwill and Other Intangible Assets (Other Intangible Assets) (Details 2) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Amortized Intangible Assets [Line Items]
Gross Carrying Amount	$ 440,661	$ 440,105
Accumulated Amortization	190,405	176,844
Net Carrying Amount	250,256	263,261
Indefinite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	128,557	99,052
Trade Names and Trademarks [Member]
Indefinite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	81,607	80,102
Franchise Agreements [Member]
Indefinite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	28,000	0
FCC licenses [Member]
Indefinite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	18,800	18,800
Licensure and Accreditation [Member]
Indefinite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	150	150
Student and Customer Relationships [Member]
Amortized Intangible Assets [Line Items]
Gross Carrying Amount	283,114	282,761
Accumulated Amortization	123,154	114,429
Net Carrying Amount	$ 159,960	$ 168,332
Student and Customer Relationships [Member] | Minimum [Member]
Amortized Intangible Assets [Line Items]
Useful Life	2 years	2 years
Student and Customer Relationships [Member] | Maximum [Member]
Amortized Intangible Assets [Line Items]
Useful Life	10 years	10 years
Trade Names and Trademarks [Member]
Amortized Intangible Assets [Line Items]
Gross Carrying Amount	$ 87,464	$ 87,285
Accumulated Amortization	42,136	39,825
Net Carrying Amount	$ 45,328	$ 47,460
Trade Names and Trademarks [Member] | Minimum [Member]
Amortized Intangible Assets [Line Items]
Useful Life	2 years	2 years
Trade Names and Trademarks [Member] | Maximum [Member]
Amortized Intangible Assets [Line Items]
Useful Life	10 years	10 years
Network Affiliation Agreements [Member]
Amortized Intangible Assets [Line Items]
Useful Life	10 years	10 years
Gross Carrying Amount	$ 17,400	$ 17,400
Accumulated Amortization	3,843	3,408
Net Carrying Amount	13,557	13,992
Databases and Technology [Member]
Amortized Intangible Assets [Line Items]
Gross Carrying Amount	27,059	27,041
Accumulated Amortization	9,702	8,471
Net Carrying Amount	$ 17,357	$ 18,570
Databases and Technology [Member] | Minimum [Member]
Amortized Intangible Assets [Line Items]
Useful Life	3 years	3 years
Databases and Technology [Member] | Maximum [Member]
Amortized Intangible Assets [Line Items]
Useful Life	6 years	6 years
Non-compete Agreements [Member]
Amortized Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,094	$ 1,088
Accumulated Amortization	869	838
Net Carrying Amount	$ 225	$ 250
Non-compete Agreements [Member] | Minimum [Member]
Amortized Intangible Assets [Line Items]
Useful Life	2 years	2 years
Non-compete Agreements [Member] | Maximum [Member]
Amortized Intangible Assets [Line Items]
Useful Life	5 years	5 years
Other [Member]
Amortized Intangible Assets [Line Items]
Gross Carrying Amount	$ 24,530	$ 24,530
Accumulated Amortization	10,701	9,873
Net Carrying Amount	$ 13,829	$ 14,657
Other [Member] | Minimum [Member]
Amortized Intangible Assets [Line Items]
Useful Life	1 year	1 year
Other [Member] | Maximum [Member]
Amortized Intangible Assets [Line Items]
Useful Life	8 years	8 years