Segment Information (Summary Of Inter-Segment Eliminations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Revenues, net	$ 634,646	$ 632,165	$ 2,026,057	$ 1,901,985
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues, net	(5,087)	(3,578)	(12,273)	(4,452)
Intersegment Eliminations [Member] | National Networks [Member]
Segment Reporting Information [Line Items]
Revenues, net	(5,079)	(3,563)	(12,015)	(4,351)
Intersegment Eliminations [Member] | International And Other [Member]
Segment Reporting Information [Line Items]
Revenues, net	$ (8)	$ (15)	$ (258)	$ (101)