Goodwill and Other Intangible Assets (Other Intangible Assets) (Details 2) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Amortized Intangible Assets [Line Items]
Gross Carrying Amount	$ 480,913	$ 481,950
Accumulated Amortization	290,872	277,304
Net Carrying Amount	190,041	204,646
Indefinite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	121,050	120,437
Trade Names and Trademarks [Member]
Indefinite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	88,042	87,429
Franchise Agreements [Member]
Indefinite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	21,858	21,858
FCC licenses [Member]
Indefinite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	11,000	11,000
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	293,481	294,077
Accumulated Amortization	185,781	178,075
Net Carrying Amount	$ 107,700	$ 116,002
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	$ 109,485	$ 109,809
Accumulated Amortization	57,667	54,766
Net Carrying Amount	$ 51,818	$ 55,043
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	7,322	6,888
Net Carrying Amount	10,078	10,512
Databases and Technology [Member]
Amortized Intangible Assets [Line Items]
Gross Carrying Amount	34,747	34,864
Accumulated Amortization	21,572	19,924
Net Carrying Amount	$ 13,175	$ 14,940
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	$ 1,000	$ 1,000
Accumulated Amortization	963	937
Net Carrying Amount	$ 37	$ 63
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	$ 24,800	$ 24,800
Accumulated Amortization	17,567	16,714
Net Carrying Amount	$ 7,233	$ 8,086
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