Recent Transactions - Pending Transactions -Additional Information (Detail) - USD ($) $ in Thousands				3 Months Ended	12 Months Ended
	Sep. 10, 2020	Apr. 06, 2020	Feb. 05, 2020	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Agreement to sell business					$ 189	$ 20,741
Radio Stations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Agreement to sell business	$ 3,500	$ 200	$ 4,000
Pretax loss on sale of assets				$ 1,400		$ 1,500