Annual report pursuant to Section 13 and 15(d)

Acquisitions and Recent Transactions - Divestitures - Additional Information (Detail)

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Acquisitions and Recent Transactions - Divestitures - Additional Information (Detail) - USD ($)
$ in Thousands
 1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended
Aug. 28, 2018
Jun. 28, 2018
Aug. 06, 2018
Jun. 30, 2018
Jun. 20, 2018
May 24, 2018
Apr. 30, 2018
Oct. 31, 2018
Jun. 30, 2018
Dec. 31, 2018
Dec. 31, 2017
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]                      
Proceeds from sale of assets                   $ 9,894 $ 2,456
Proceeds from sale of property, plant, and equipment           $ 800          
Agreement to sell assets in cash           1,000          
Gain (loss) on disposition of assets           $ (200)          
Time Brokerage Agreement [Member]                      
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]                      
Payments to acquire businesses, gross             $ 1,200        
Fee for not exercising purchase option             $ 100        
KGBIFM [Member]                      
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]                      
Proceeds from sale of assets     $ 3,200                
Gain (loss) on disposition of assets     $ (2,400)           $ (3,200)    
Omaha KCRO-AM and KOTK-AM [Member]                      
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]                      
Proceeds from sale of assets               $ 1,400      
Gain (loss) on disposition of assets       $ (1,600)       $ (100)      
WQVN-AM [Member]                      
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]                      
Proceeds from sale of assets $ 3,500                    
Gain (loss) on disposition of assets $ (4,700)                    
WBIX-AM [Member]                      
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]                      
Proceeds from sale of assets         $ 700            
Gain (loss) on disposition of assets         $ 200            
Lakeside [Member]                      
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]                      
Proceeds from sale of assets   $ 300