Revenues - Summary of Revenues Disaggregated by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Total revenue	$ 171,683	$ 62,978	$ 45,116	$ 64,249	$ 70,838	$ 68,816	$ 69,241	$ 64,680	$ 344,026	$ 273,575	$ 297,815
Broadcast Advertising
Disaggregation Of Revenue [Line Items]
Total revenue									152,677	148,082	169,009
Digital Advertising
Disaggregation Of Revenue [Line Items]
Total revenue									143,309	68,908	80,982
Spectrum Usage Rights
Disaggregation Of Revenue [Line Items]
Total revenue									5,429	13,061	2,976
Retransmission Consent
Disaggregation Of Revenue [Line Items]
Total revenue									36,766	35,362	35,066
Other
Disaggregation Of Revenue [Line Items]
Total revenue									$ 5,845	$ 8,162	$ 9,782