Other Non-Operating Income (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2022	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Non-Operating Income [Line Items]
Net gain on sale of businesses				$ 22,679	$ 3,789	$ 213,302
Gain on acquiring a controlling interest in an equity affiliate				0	0	3,708
Framebridge [Member]
Schedule of Non-Operating Income [Line Items]
Gain on acquiring a controlling interest in an equity affiliate			$ 3,700
Megaphone [Member]
Schedule of Non-Operating Income [Line Items]
Net gain on sale of businesses		$ 209,800
CyberVista [Member]
Schedule of Non-Operating Income [Line Items]
Net gain on sale of businesses	$ 18,400
Education [Member] | Higher Education [Member] | Kaplan University Transaction [Member]
Schedule of Non-Operating Income [Line Items]
Gain related to contingent consideration				$ 4,300	$ 3,900	$ 3,500