Investments Career Builder (Details) - CareerBuilder, LLC and Dose Media, LLC - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Equity Method Investments [Line Items]
Revenues, net	$ 119,502	$ 165,961	$ 432,330	$ 505,383
Operating income (loss)	10,698	(9,661)	26,759	373
Net income (loss)	$ 3,884	$ (14,090)	$ 102,541	$ (842)