Investments TV Food Network (Details) - Television Food Network, G.P. - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Revenues, net	$ 1,263,279	$ 1,208,357	$ 1,160,716
Operating income	654,296	593,409	535,131
Net income	670,738	608,327	$ 552,146
Current assets	800,990	840,763
Non-current assets	347,688	150,277
Current liabilities	108,568	92,193
Non-current liabilities	$ 109	$ 0