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Assets Held for Sale and Discontinued Operations - Additional Information (Details) - Radio Segment - Disposed of by sale
$ in Thousands
3 Months Ended
Mar. 31, 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 | $ $ 20,000