Other Non-Operating Income (Narrative) (Details) $ in Thousands	3 Months Ended					6 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) business	Dec. 31, 2017 USD ($)
Schedule of Non-Operating Income [Line Items]
Impairment of cost method investments									$ (200)
Gain on sale of an equity affiliate							$ 28,994	$ 0	0
Gains on cost method investments	$ 3,700	$ 1,300	$ 3,200	$ 8,500			5,080	11,663	0
Loss on Guarantor Lease Obligations							1,075	17,518	0
Net (loss) gain on sales of businesses							(564)	8,157	$ (569)
Sale Of KHE Campuses Business [Member]
Schedule of Non-Operating Income [Line Items]
Loss on Guarantor Lease Obligations						$ 17,500	1,100	17,500
Education [Member]
Schedule of Non-Operating Income [Line Items]
Net (loss) gain on sales of businesses								$ 8,200
Number Of Businesses Disposed | business								3
Gimlet Media [Member]
Schedule of Non-Operating Income [Line Items]
Gain on sale of an equity affiliate		$ 29,000
Higher Education [Member] | Education [Member] | Kaplan University Transaction [Member]
Schedule of Non-Operating Income [Line Items]
Net (loss) gain on sales of businesses			$ 4,300		$ 4,300			$ 4,300
Gain Related to Contingent Consideration							$ 1,400	$ 1,900