Assets Held for Sale and Discontinued Operations - Additional Information (Details) - Radio Segment - Disposed of by sale $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 radio_station
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of radio stations \| radio_station			34
Impairment of goodwill \| $	$ 0	$ 25,900

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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