Goodwill and Other Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Reduction in carrying amount of goodwill		$ (996)
Impairment charge related to goodwill		25,062
Aggregate amortization expense for amortizable intangible assets		32,600	$ 34,200
Impairment charge related to intangible assets	$ 105,300
AMCNI
Finite-Lived Intangible Assets [Line Items]
Impairment charge related to goodwill		25,100
National Networks
Finite-Lived Intangible Assets [Line Items]
Reduction in carrying amount of goodwill		(996)
Impairment charge related to goodwill		0
International and Other
Finite-Lived Intangible Assets [Line Items]
Accumulated impairment charges	$ 123,100	123,100		$ 98,000
Reduction in carrying amount of goodwill		0
Impairment charge related to goodwill		$ 25,062