Assets Held for Sale and Discontinued Operations - Operating Results of Discontinued Operations (Details) - Radio Segment - Disposed of by sale - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenues	$ 17,386		$ 30,685
Total costs and expenses	(13,421)		(24,937)
Impairment of goodwill and intangible assets	(5,900)	$ (20,000)	(25,900)
Other, net	(9)		(157)
Loss from discontinued operations before income taxes	(1,944)		(20,309)
Provision (benefit) for income taxes	998		1,137
Net loss from discontinued operations	$ (2,942)		$ (21,446)