Investments Career Builder and Dose Media Summarized Financial Information (Details) - CareerBuilder, LLC and Dose Media, LLC - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Revenues, net	$ 433,757	[1]	$ 645,790	$ 719,994
Operating income	25,791	[1]	(10,457)	93,619
Net income	101,573	[1]	(19,125)	$ 89,249
Current assets	1,653	[2]	180,828
Non-current assets	246	[2]	503,688
Current liabilities	566	[2]	196,101
Non-current liabilities	$ 0	[2]	$ 319,037

[1] (1)Revenues, net, operating income (loss) and net income (loss) that relate to CareerBuilder include results through September 13, 2018.

[2] (1)Summarized balance sheet information at December 31, 2018 excludes CareerBuilder as the investment was sold on September 13, 2018.