Description Of Business And Basis Of Presentation (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment network	Sep. 30, 2017 USD ($)	Jan. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated earnings	$ 1,157,063		$ 1,157,063			$ 766,725
Number of Operating Segments | segment			2
Number of Nationally Distributed Programming Networks | network			5
Program Rights Write Offs	$ 11,400	$ 8,000	$ 20,600	$ 9,700
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated earnings					$ 12,800