Restructuring (Restructuring and Related Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring expense	$ 6,128	$ 29,503	$ 14,998
National Networks [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense	(53)	8,516	3,194
International And Other [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense	$ 6,181	$ 20,987	$ 11,804