Revenues - Summary of Disaggregation of Broadcast Advertising Revenue by Sales Channel (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation Of Revenue [Line Items]
Total revenue	$ 70,838	$ 68,816	$ 69,241	$ 64,680	$ 82,073	$ 74,575	$ 74,329	$ 66,838	$ 273,575	$ 297,815	$ 536,034
Advertising
Disaggregation Of Revenue [Line Items]
Total revenue									148,082	169,009	171,715
Advertising | Local Direct
Disaggregation Of Revenue [Line Items]
Total revenue									25,972	27,522	30,343
Advertising | Local Agency
Disaggregation Of Revenue [Line Items]
Total revenue									58,425	61,226	64,724
Advertising | National Agency
Disaggregation Of Revenue [Line Items]
Total revenue									$ 63,685	$ 80,261	$ 76,648