Broadcast Licenses, Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended														12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016		Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Indefinite-lived Intangible Assets [Line Items]
Balance				$ 86,622								$ 88,106			$ 86,622	$ 88,106
Acquisitions															8,086	8,123
Dispositions															(9,607)
Impairment charge	$ (1,449)	$ 0	$ 0	0	[1]	$ 0	[1]	$ 0		$ 0		0	[1]	$ (874)	(1,449)	0	$ (874)
Balance	93,259					86,622								88,106	93,259	86,622	88,106
Discontinued Operations [Member]
Indefinite-lived Intangible Assets [Line Items]
Balance				9,607								9,607			9,607	9,607
Acquisitions															0	0
Dispositions															(9,607)
Impairment charge															0
Balance	0					9,607								9,607	0	9,607	9,607
Continuing Operations [Member]
Indefinite-lived Intangible Assets [Line Items]
Balance				$ 86,622								$ 78,499			86,622	78,499
Acquisitions															8,086	8,123
Dispositions															0
Impairment charge															(1,449)
Balance	$ 93,259					$ 86,622								$ 78,499	$ 93,259	$ 86,622	$ 78,499

[1] Certain prior year amounts and March 31, 2017 quarterly data have been reclassified to conform with current presentation.