Quarterly report pursuant to Section 13 or 15(d)

Recent Transactions - Divestitures - Additional Information (Detail)

v3.20.2
Recent Transactions - Divestitures - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 10, 2020
Apr. 06, 2020
Feb. 05, 2020
Dec. 31, 2020
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]              
Proceeds from sale of intangible assets         $ 188 $ 4,202  
Radio Stations [Member]              
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]              
Proceeds from sale of intangible assets $ 3,500 $ 200 $ 4,000        
Pretax loss on sale of assets       $ 1,400     $ 1,500